Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

fixbugs Finding section exceptions when strip removing information #9

Closed
wants to merge 1 commit into from
Closed

fixbugs Finding section exceptions when strip removing information #9

wants to merge 1 commit into from

Conversation

kiraskyler
Copy link

@kiraskyler kiraskyler commented Sep 26, 2023 •
edited
Loading

Exception occurred while strip removing information

strip -g /root/rpmbuild/BUILDROOT/glibc-2.28-226.cy8.aarch64/usr/lib64/gcrt1.o
strip:/root/rpmbuild/BUILDROOT/glibc-2.28-226.cy8.aarch64/usr/lib64/stViQ9wt[.gnu.build.attributes.hot]: error: failed to copy merged notes into output: Bad value

The reason is that this elf has a section with a duplicate name that needs to be removed

[root@localhost ~]# readelf -t ./gcrt1.o |grep attributes.hot
  [63] .gnu.build.attributes.hot
  [64] .rela.gnu.build.attributes.hot
  [71] .gnu.build.attributes.hot
  [72] .rela.gnu.build.attributes.hot
  [79] .gnu.build.attributes.hot
  [80] .rela.gnu.build.attributes.hot

Merged_ Note_ Sections are inverted linked lists, while obfd ->sections are positive linked lists, and there will be sections that need to be processed if errors are found

@kiraskyler kiraskyler closed this by deleting the head repository Sep 26, 2023
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@T-J-Teru
gdb: don't restart vfork parent while waiting for child to finish
14ec417 
While working on a later patch, which changes gdb.base/foll-vfork.exp,
I noticed that sometimes I would hit this assert:

  x86_linux_update_debug_registers: Assertion `lwp_is_stopped (lwp)' failed.

I eventually tracked it down to a combination of schedule-multiple
mode being on, target-non-stop being off, follow-fork-mode being set
to child, and some bad timing.  The failing case is pretty simple, a
single threaded application performs a vfork, the child process then
execs some other application while the parent process (once the vfork
child has completed its exec) just exits.  As best I understand
things, here's what happens when things go wrong:

  1. The parent process performs a vfork, GDB sees the VFORKED event
  and creates an inferior and thread for the vfork child,

  2. GDB resumes the vfork child process.  As schedule-multiple is on
  and target-non-stop is off, this is translated into a request to
  start all processes (see user_visible_resume_ptid),

  3. In the linux-nat layer we spot that one of the threads we are
  about to start is a vfork parent, and so don't start that
  thread (see resume_lwp), the vfork child thread is resumed,

  4. GDB waits for the next event, eventually entering
  linux_nat_target::wait, which in turn calls linux_nat_wait_1,

  5. In linux_nat_wait_1 we eventually call
  resume_stopped_resumed_lwps, this should restart threads that have
  stopped but don't actually have anything interesting to report.

  6. Unfortunately, resume_stopped_resumed_lwps doesn't check for
  vfork parents like resume_lwp does, so at this point the vfork
  parent is resumed.  This feels like the start of the bug, and this
  is where I'm proposing to fix things, but, resuming the vfork parent
  isn't the worst thing in the world because....

  7. As the vfork child is still alive the kernel holds the vfork
  parent stopped,

  8. Eventually the child performs its exec and GDB is sent and EXECD
  event.  However, because the parent is resumed, as soon as the child
  performs its exec the vfork parent also sends a VFORK_DONE event to
  GDB,

  9. Depending on timing both of these events might seem to arrive in
  GDB at the same time.  Normally GDB expects to see the EXECD or
  EXITED/SIGNALED event from the vfork child before getting the
  VFORK_DONE in the parent.  We know this because it is as a result of
  the EXECD/EXITED/SIGNALED that GDB detaches from the parent (see
  handle_vfork_child_exec_or_exit for details).  Further the comment
  in target/waitstatus.h on TARGET_WAITKIND_VFORK_DONE indicates that
  when we remain attached to the child (not the parent) we should not
  expect to see a VFORK_DONE,

  10. If both events arrive at the same time then GDB will randomly
  choose one event to handle first, in some cases this will be the
  VFORK_DONE.  As described above, upon seeing a VFORK_DONE GDB
  expects that (a) the vfork child has finished, however, in this case
  this is not completely true, the child has finished, but GDB has not
  processed the event associated with the completion yet, and (b) upon
  seeing a VFORK_DONE GDB assumes we are remaining attached to the
  parent, and so resumes the parent process,

  11. GDB now handles the EXECD event.  In our case we are detaching
  from the parent, so GDB calls target_detach (see
  handle_vfork_child_exec_or_exit),

  12. While this has been going on the vfork parent is executing, and
  might even exit,

  13. In linux_nat_target::detach the first thing we do is stop all
  threads in the process we're detaching from, the result of the stop
  request will be cached on the lwp_info object,

  14. In our case the vfork parent has exited though, so when GDB
  waits for the thread, instead of a stop due to signal, we instead
  get a thread exited status,

  15. Later in the detach process we try to resume the threads just
  prior to making the ptrace call to actually detach (see
  detach_one_lwp), as part of the process to resume a thread we try to
  touch some registers within the thread, and before doing this GDB
  asserts that the thread is stopped,

  16. An exited thread is not classified as stopped, and so the assert
  triggers!

So there's two bugs I see here.  The first, and most critical one here
is in step bminor#6.  I think that resume_stopped_resumed_lwps should not
resume a vfork parent, just like resume_lwp doesn't resume a vfork
parent.

With this change in place the vfork parent will remain stopped in step
instead GDB will only see the EXECD/EXITED/SIGNALLED event.  The
problems in bminor#9 and bminor#10 are therefore skipped and we arrive at bminor#11,
handling the EXECD event.  As the parent is still stopped bminor#12 doesn't
apply, and in #13 when we try to stop the process we will see that it
is already stopped, there's no risk of the vfork parent exiting before
we get to this point.  And finally, in #15 we are safe to poke the
process registers because it will not have exited by this point.

However, I did mention two bugs.

The second bug I've not yet managed to actually trigger, but I'm
convinced it must exist: if we forget vforks for a moment, in step #13
above, when linux_nat_target::detach is called, we first try to stop
all threads in the process GDB is detaching from.  If we imagine a
multi-threaded inferior with many threads, and GDB running in non-stop
mode, then, if the user tries to detach there is a chance that thread
could exit just as linux_nat_target::detach is entered, in which case
we should be able to trigger the same assert.

But, like I said, I've not (yet) managed to trigger this second bug,
and even if I could, the fix would not belong in this commit, so I'm
pointing this out just for completeness.

There's no test included in this commit.  In a couple of commits time
I will expand gdb.base/foll-vfork.exp which is when this bug would be
exposed.  Unfortunately there are at least two other bugs (separate
from the ones discussed above) that need fixing first, these will be
fixed in the next commits before the gdb.base/foll-vfork.exp test is
expanded.

If you do want to reproduce this failure then you will for certainly
need to run the gdb.base/foll-vfork.exp test in a loop as the failures
are all very timing sensitive.  I've found that running multiple
copies in parallel makes the failure more likely to appear, I usually
run ~6 copies in parallel and expect to see a failure after within
10mins.
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix data race on index_cache::m_enabled
8adc552 
With gdb build with -fsanitize=thread and test-case gdb.base/index-cache.exp I
run into:
...
(gdb) file build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache
Reading symbols from build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache...
(gdb) show index-cache enabled
The index cache is off.
(gdb) PASS: gdb.base/index-cache.exp: test_basic_stuff: index-cache is disabled by default
set index-cache enabled on
==================
WARNING: ThreadSanitizer: data race (pid=32248)
  Write of size 1 at 0x00000321f540 by main thread:
    #0 index_cache::enable() gdb/dwarf2/index-cache.c:76 (gdb+0x82cfdd)
    bminor#1 set_index_cache_enabled_command gdb/dwarf2/index-cache.c:270 (gdb+0x82d9af)
    bminor#2 bool setting::set<bool>(bool const&) gdb/command.h:353 (gdb+0x6fe5f2)
    bminor#3 do_set_command(char const*, int, cmd_list_element*) gdb/cli/cli-setshow.c:414 (gdb+0x6fcd21)
    bminor#4 execute_command(char const*, int) gdb/top.c:567 (gdb+0xff2e64)
    bminor#5 command_handler(char const*) gdb/event-top.c:552 (gdb+0x94acc0)
    bminor#6 command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:788 (gdb+0x94b37d)
    bminor#7 tui_command_line_handler gdb/tui/tui-interp.c:104 (gdb+0x103467e)
    bminor#8 gdb_rl_callback_handler gdb/event-top.c:259 (gdb+0x94a265)
    bminor#9 rl_callback_read_char readline/readline/callback.c:290 (gdb+0x11bdd3f)
    bminor#10 gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195 (gdb+0x94a064)
    bminor#11 gdb_rl_callback_read_char_wrapper gdb/event-top.c:234 (gdb+0x94a125)
    bminor#12 stdin_event_handler gdb/ui.c:155 (gdb+0x1074922)
    #13 handle_file_event gdbsupport/event-loop.cc:573 (gdb+0x1d94de4)
    #14 gdb_wait_for_event gdbsupport/event-loop.cc:694 (gdb+0x1d9551c)
    #15 gdb_do_one_event(int) gdbsupport/event-loop.cc:264 (gdb+0x1d93908)
    #16 start_event_loop gdb/main.c:412 (gdb+0xb5a256)
    #17 captured_command_loop gdb/main.c:476 (gdb+0xb5a445)
    #18 captured_main gdb/main.c:1320 (gdb+0xb5c5c5)
    #19 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xb5c674)
    #20 main gdb/gdb.c:32 (gdb+0x416776)

  Previous read of size 1 at 0x00000321f540 by thread T12:
    #0 index_cache::enabled() const gdb/dwarf2/index-cache.h:48 (gdb+0x82e1a6)
    bminor#1 index_cache::store(dwarf2_per_bfd*) gdb/dwarf2/index-cache.c:94 (gdb+0x82d0bc)
    bminor#2 cooked_index::maybe_write_index(dwarf2_per_bfd*) gdb/dwarf2/cooked-index.c:638 (gdb+0x7f1b97)
    bminor#3 operator() gdb/dwarf2/cooked-index.c:468 (gdb+0x7f0f24)
    bminor#4 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x7f285b)
    bminor#5 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x700952)
    bminor#6 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x7381a0)
    bminor#7 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x737e91)
    bminor#8 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x737b59)
    bminor#9 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x738660)
    bminor#10 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x73825c)
    bminor#11 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x733623)
    bminor#12 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x732bdf)
    #13 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x734c4f)
    #14 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x733bc5)
    #15 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x73300d)
    #16 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x7330b2)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x7330f2)
    #18 pthread_once <null> (libtsan.so.0+0x4457c)
    #19 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72f5dd)
    #20 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x733224)
    #21 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x732852)
    #22 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x737bef)
    #23 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x1dac492)
    #24 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x1dabdb4)
    #25 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x1dace63)
    #26 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x1dac294)
    #27 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x1daf5c6)
    #28 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x1daf551)
    #29 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x1daf506)
    #30 <null> <null> (libstdc++.so.6+0xdcac2)

  Location is global 'global_index_cache' of size 48 at 0x00000321f520 (gdb+0x00000321f540)
  ...
SUMMARY: ThreadSanitizer: data race gdb/dwarf2/index-cache.c:76 in index_cache::enable()
...

The race happens when issuing a "file $exec" command followed by a
"set index-cache enabled on" command.

The race is between:
- a worker thread reading index_cache::m_enabled to determine whether an
  index-cache entry for $exec needs to be written
  (due to command "file $exec"), and
- the main thread setting index_cache::m_enabled
  (due to command "set index-cache enabled on").

Fix this by capturing the value of index_cache::m_enabled in the main thread,
and using the captured value in the worker thread.

Tested on x86_64-linux.

PR symtab/30392
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30392
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix data race on bfd::{cacheable,format}
488b3ff 
With gdb build with -fsanitize=thread and test-case gdb.base/index-cache.exp I
run into:
...
(gdb) file build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache
Reading symbols from build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache...
==================
WARNING: ThreadSanitizer: data race (pid=12261)
  Write of size 4 at 0x7b4400097d08 by main thread:
    #0 bfd_open_file bfd/cache.c:584 (gdb+0x148bb92)
    bminor#1 bfd_cache_lookup_worker bfd/cache.c:261 (gdb+0x148b12a)
    bminor#2 cache_bseek bfd/cache.c:289 (gdb+0x148b324)
    bminor#3 bfd_seek bfd/bfdio.c:459 (gdb+0x1489c31)
    bminor#4 _bfd_generic_get_section_contents bfd/libbfd.c:1069 (gdb+0x14977a4)
    bminor#5 bfd_get_section_contents bfd/section.c:1606 (gdb+0x149cc7c)
    bminor#6 gdb_bfd_scan_elf_dyntag(int, bfd*, unsigned long*, unsigned long*) gdb/solib.c:1601 (gdb+0xed8eca)
    bminor#7 elf_locate_base gdb/solib-svr4.c:705 (gdb+0xec28ac)
    bminor#8 svr4_iterate_over_objfiles_in_search_order gdb/solib-svr4.c:3430 (gdb+0xeca55d)
    bminor#9 gdbarch_iterate_over_objfiles_in_search_order(gdbarch*, gdb::function_view<bool (objfile*)>, objfile*) gdb/gdbarch.c:5041 (gdb+0x537cad)
    bminor#10 find_main_name gdb/symtab.c:6270 (gdb+0xf743a5)
    bminor#11 main_language() gdb/symtab.c:6313 (gdb+0xf74499)
    bminor#12 set_initial_language() gdb/symfile.c:1700 (gdb+0xf4285c)
    #13 symbol_file_add_main_1 gdb/symfile.c:1212 (gdb+0xf40e2a)
    #14 symbol_file_command(char const*, int) gdb/symfile.c:1681 (gdb+0xf427d1)
    #15 file_command gdb/exec.c:554 (gdb+0x94f74b)
    #16 do_simple_func gdb/cli/cli-decode.c:95 (gdb+0x6d9528)
    #17 cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735 (gdb+0x6e0f69)
    #18 execute_command(char const*, int) gdb/top.c:575 (gdb+0xff303c)
    #19 command_handler(char const*) gdb/event-top.c:552 (gdb+0x94adde)
    #20 command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:788 (gdb+0x94b49b)
    #21 tui_command_line_handler gdb/tui/tui-interp.c:104 (gdb+0x103479c)
    #22 gdb_rl_callback_handler gdb/event-top.c:259 (gdb+0x94a383)
    #23 rl_callback_read_char readline/readline/callback.c:290 (gdb+0x11bde5d)
    #24 gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195 (gdb+0x94a182)
    #25 gdb_rl_callback_read_char_wrapper gdb/event-top.c:234 (gdb+0x94a243)
    #26 stdin_event_handler gdb/ui.c:155 (gdb+0x1074a40)
    #27 handle_file_event gdbsupport/event-loop.cc:573 (gdb+0x1d94f02)
    #28 gdb_wait_for_event gdbsupport/event-loop.cc:694 (gdb+0x1d9563a)
    #29 gdb_do_one_event(int) gdbsupport/event-loop.cc:264 (gdb+0x1d93a26)
    #30 start_event_loop gdb/main.c:412 (gdb+0xb5a374)
    #31 captured_command_loop gdb/main.c:476 (gdb+0xb5a563)
    #32 captured_main gdb/main.c:1320 (gdb+0xb5c6e3)
    #33 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xb5c792)
    #34 main gdb/gdb.c:32 (gdb+0x416776)

  Previous read of size 1 at 0x7b4400097d08 by thread T12:
    #0 bfd_check_format_matches bfd/format.c:323 (gdb+0x1492db4)
    bminor#1 bfd_check_format bfd/format.c:94 (gdb+0x1492104)
    bminor#2 build_id_bfd_get(bfd*) gdb/build-id.c:42 (gdb+0x6648f7)
    bminor#3 index_cache::store(dwarf2_per_bfd*, index_cache_store_context*) gdb/dwarf2/index-cache.c:110 (gdb+0x82d205)
    bminor#4 cooked_index::maybe_write_index(dwarf2_per_bfd*) gdb/dwarf2/cooked-index.c:640 (gdb+0x7f1bf1)
    bminor#5 operator() gdb/dwarf2/cooked-index.c:470 (gdb+0x7f0f40)
    bminor#6 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x7f28f7)
    bminor#7 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x700952)
    bminor#8 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x7381a0)
    bminor#9 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x737e91)
    bminor#10 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x737b59)
    bminor#11 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x738660)
    bminor#12 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x73825c)
    #13 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x733623)
    #14 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x732bdf)
    #15 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x734c4f)
    #16 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x733bc5)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x73300d)
    #18 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x7330b2)
    #19 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x7330f2)
    #20 pthread_once <null> (libtsan.so.0+0x4457c)
    #21 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72f5dd)
    #22 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x733224)
    #23 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x732852)
    #24 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x737bef)
    #25 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x1dac5b0)
    #26 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x1dabed2)
    #27 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x1dacf81)
    #28 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x1dac3b2)
    #29 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x1daf6e4)
    #30 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x1daf66f)
    #31 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x1daf624)
    #32 <null> <null> (libstdc++.so.6+0xdcac2)
  ...
SUMMARY: ThreadSanitizer: data race bfd/cache.c:584 in bfd_open_file
...

The race happens when issuing the "file $exec" command.

The race is between:
- a worker thread getting the build id while writing the index cache, and in
  the process reading bfd::format, and
- the main thread calling find_main_name, and in the process setting
  bfd::cacheable.

The two bitfields bfd::cacheable and bfd::format share the same bitfield
container.

Fix this by capturing the build id in the main thread, and using the captured
value in the worker thread.

Likewise for the dwz build id, which likely suffers from the same issue.

While we're at it, also move the creation of the cache directory to
the index_cache_store_context constructor, to:
- make sure there's no race between subsequent file commands, and
- issue any related warning or error messages during the file command.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

PR symtab/30392
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30392
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix race on dwarf2_per_cu_data::{queued,is_debug_type}
12afdee 
With gdb build with -fsanitize=thread and test-case gdb.base/index-cache.exp I
run into:
...
(gdb) file build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache
Reading symbols from build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache...
==================
WARNING: ThreadSanitizer: data race (pid=24296)
  Write of size 1 at 0x7b200000420d by main thread:
    #0 queue_comp_unit gdb/dwarf2/read.c:5564 (gdb+0x8939ce)
    bminor#1 dw2_do_instantiate_symtab gdb/dwarf2/read.c:1754 (gdb+0x885b96)
    bminor#2 dw2_instantiate_symtab gdb/dwarf2/read.c:1792 (gdb+0x885d86)
    bminor#3 dw2_expand_symtabs_matching_one(dwarf2_per_cu_data*, dwarf2_per_objfile*, gdb::function_view<bool (char const*, bool)>, gdb::function_view<bool (compunit_symtab*)>) gdb/dwarf2/read.c:3042 (gdb+0x88ac77)
    bminor#4 cooked_index_functions::expand_symtabs_matching(objfile*, gdb::function_view<bool (char const*, bool)>, lookup_name_info const*, gdb::function_view<bool (char const*)>, gdb::function_view<bool (compunit_symtab*)>, enum_flags<block_search_flag_values>, domain_enum, search_domain) gdb/dwarf2/read.c:16915 (gdb+0x8c1c8a)
    bminor#5 objfile::lookup_symbol(block_enum, char const*, domain_enum) gdb/symfile-debug.c:288 (gdb+0xf389a1)
    bminor#6 lookup_symbol_via_quick_fns gdb/symtab.c:2385 (gdb+0xf66403)
    bminor#7 lookup_symbol_in_objfile gdb/symtab.c:2516 (gdb+0xf66a67)
    bminor#8 operator() gdb/symtab.c:2562 (gdb+0xf66bbe)
    bminor#9 operator() gdb/../gdbsupport/function-view.h:305 (gdb+0xf76ffd)
    bminor#10 _FUN gdb/../gdbsupport/function-view.h:299 (gdb+0xf77054)
    bminor#11 gdb::function_view<bool (objfile*)>::operator()(objfile*) const gdb/../gdbsupport/function-view.h:289 (gdb+0xc3f5e3)
    bminor#12 svr4_iterate_over_objfiles_in_search_order gdb/solib-svr4.c:3455 (gdb+0xeca793)
    #13 gdbarch_iterate_over_objfiles_in_search_order(gdbarch*, gdb::function_view<bool (objfile*)>, objfile*) gdb/gdbarch.c:5041 (gdb+0x537cad)
    #14 lookup_global_or_static_symbol gdb/symtab.c:2559 (gdb+0xf66e47)
    #15 lookup_global_symbol(char const*, block const*, domain_enum) gdb/symtab.c:2615 (gdb+0xf670cc)
    #16 language_defn::lookup_symbol_nonlocal(char const*, block const*, domain_enum) const gdb/symtab.c:2447 (gdb+0xf666ba)
    #17 lookup_symbol_aux gdb/symtab.c:2123 (gdb+0xf655ff)
    #18 lookup_symbol_in_language(char const*, block const*, domain_enum, language, field_of_this_result*) gdb/symtab.c:1931 (gdb+0xf646f7)
    #19 set_initial_language() gdb/symfile.c:1708 (gdb+0xf429c0)
    #20 symbol_file_add_main_1 gdb/symfile.c:1212 (gdb+0xf40f54)
    #21 symbol_file_command(char const*, int) gdb/symfile.c:1681 (gdb+0xf428fb)
    #22 file_command gdb/exec.c:554 (gdb+0x94f875)
    #23 do_simple_func gdb/cli/cli-decode.c:95 (gdb+0x6d9528)
    #24 cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735 (gdb+0x6e0f69)
    #25 execute_command(char const*, int) gdb/top.c:575 (gdb+0xff3166)
    #26 command_handler(char const*) gdb/event-top.c:552 (gdb+0x94af08)
    #27 command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:788 (gdb+0x94b5c5)
    #28 tui_command_line_handler gdb/tui/tui-interp.c:104 (gdb+0x10348c6)
    #29 gdb_rl_callback_handler gdb/event-top.c:259 (gdb+0x94a4ad)
    #30 rl_callback_read_char readline/readline/callback.c:290 (gdb+0x11bdf87)
    #31 gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195 (gdb+0x94a2ac)
    #32 gdb_rl_callback_read_char_wrapper gdb/event-top.c:234 (gdb+0x94a36d)
    #33 stdin_event_handler gdb/ui.c:155 (gdb+0x1074b6a)
    #34 handle_file_event gdbsupport/event-loop.cc:573 (gdb+0x1d9502c)
    #35 gdb_wait_for_event gdbsupport/event-loop.cc:694 (gdb+0x1d95764)
    #36 gdb_do_one_event(int) gdbsupport/event-loop.cc:264 (gdb+0x1d93b50)
    #37 start_event_loop gdb/main.c:412 (gdb+0xb5a49e)
    #38 captured_command_loop gdb/main.c:476 (gdb+0xb5a68d)
    #39 captured_main gdb/main.c:1320 (gdb+0xb5c80d)
    #40 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xb5c8bc)
    #41 main gdb/gdb.c:32 (gdb+0x416776)

  Previous read of size 1 at 0x7b200000420d by thread T12:
    #0 write_gdbindex gdb/dwarf2/index-write.c:1229 (gdb+0x8310c8)
    bminor#1 write_dwarf_index(dwarf2_per_bfd*, char const*, char const*, char const*, dw_index_kind) gdb/dwarf2/index-write.c:1484 (gdb+0x83232f)
    bminor#2 index_cache::store(dwarf2_per_bfd*, index_cache_store_context*) gdb/dwarf2/index-cache.c:177 (gdb+0x82d62b)
    bminor#3 cooked_index::maybe_write_index(dwarf2_per_bfd*) gdb/dwarf2/cooked-index.c:640 (gdb+0x7f1bf7)
    bminor#4 operator() gdb/dwarf2/cooked-index.c:470 (gdb+0x7f0f40)
    bminor#5 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x7f2909)
    bminor#6 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x700952)
    bminor#7 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x7381a0)
    bminor#8 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x737e91)
    bminor#9 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x737b59)
    bminor#10 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x738660)
    bminor#11 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x73825c)
    bminor#12 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x733623)
    #13 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x732bdf)
    #14 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x734c4f)
    #15 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x733bc5)
    #16 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x73300d)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x7330b2)
    #18 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x7330f2)
    #19 pthread_once <null> (libtsan.so.0+0x4457c)
    #20 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72f5dd)
    #21 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x733224)
    #22 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x732852)
    #23 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x737bef)
    #24 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x1dac6da)
    #25 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x1dabffc)
    #26 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x1dad0ab)
    #27 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x1dac4dc)
    #28 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x1daf80e)
    #29 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x1daf799)
    #30 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x1daf74e)
    #31 <null> <null> (libstdc++.so.6+0xdcac2)
 ...
SUMMARY: ThreadSanitizer: data race gdb/dwarf2/read.c:5564 in queue_comp_unit
...

The race happens when issuing the "file $exec" command.

The race is between:
- a worker thread writing the index cache, and in the process reading
  dwarf2_per_cu_data::is_debug_type, and
- the main thread expanding the CU containing main, and in the process setting
  dwarf2_per_cu_data::queued.

The two bitfields dwarf2_per_cu_data::queue and
dwarf2_per_cu_data::is_debug_type share the same bitfield container.

Fix this by making dwarf2_per_cu_data::queued a packed<bool, 1>.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

PR symtab/30392
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30392
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix data race on dwarf2_per_cu_data::{m_header_read_in,i…
edb157d 
…s_debug_type}

With gdb build with -fsanitize=thread and test-case gdb.base/index-cache.exp
and target board debug-types, I run into:
...
(gdb) file build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache
Reading symbols from build/gdb/testsuite/outputs/gdb.base/index-cache/index-cache...
==================
WARNING: ThreadSanitizer: data race (pid=9654)
  Write of size 1 at 0x7b200000420d by main thread:
    #0 dwarf2_per_cu_data::get_header() const gdb/dwarf2/read.c:21513 (gdb+0x8d1eee)
    bminor#1 dwarf2_per_cu_data::addr_size() const gdb/dwarf2/read.c:21524 (gdb+0x8d1f4e)
    bminor#2 dwarf2_cu::addr_type() const gdb/dwarf2/cu.c:112 (gdb+0x806327)
    bminor#3 set_die_type gdb/dwarf2/read.c:21932 (gdb+0x8d3870)
    bminor#4 read_base_type gdb/dwarf2/read.c:15448 (gdb+0x8bcacb)
    bminor#5 read_type_die_1 gdb/dwarf2/read.c:19832 (gdb+0x8cc0a5)
    bminor#6 read_type_die gdb/dwarf2/read.c:19767 (gdb+0x8cbe6d)
    bminor#7 lookup_die_type gdb/dwarf2/read.c:19739 (gdb+0x8cbdc7)
    bminor#8 die_type gdb/dwarf2/read.c:19593 (gdb+0x8cb68a)
    bminor#9 read_subroutine_type gdb/dwarf2/read.c:14648 (gdb+0x8b998e)
    bminor#10 read_type_die_1 gdb/dwarf2/read.c:19792 (gdb+0x8cbf2f)
    bminor#11 read_type_die gdb/dwarf2/read.c:19767 (gdb+0x8cbe6d)
    bminor#12 read_func_scope gdb/dwarf2/read.c:10154 (gdb+0x8a4f36)
    #13 process_die gdb/dwarf2/read.c:6667 (gdb+0x898daa)
    #14 read_file_scope gdb/dwarf2/read.c:7682 (gdb+0x89bad8)
    #15 process_die gdb/dwarf2/read.c:6654 (gdb+0x898ced)
    #16 process_full_comp_unit gdb/dwarf2/read.c:6418 (gdb+0x8981de)
    #17 process_queue gdb/dwarf2/read.c:5690 (gdb+0x894433)
    #18 dw2_do_instantiate_symtab gdb/dwarf2/read.c:1770 (gdb+0x88623a)
    #19 dw2_instantiate_symtab gdb/dwarf2/read.c:1792 (gdb+0x886300)
    #20 dw2_expand_symtabs_matching_one(dwarf2_per_cu_data*, dwarf2_per_objfile*, gdb::function_view<bool (char const*, bool)>, gdb::function_view<bool (compunit_symtab*)>) gdb/dwarf2/read.c:3042 (gdb+0x88b1f1)
    #21 cooked_index_functions::expand_symtabs_matching(objfile*, gdb::function_view<bool (char const*, bool)>, lookup_name_info const*, gdb::function_view<bool (char const*)>, gdb::function_view<bool (compunit_symtab*)>, enum_flags<block_search_flag_values>, domain_enum, search_domain) gdb/dwarf2/read.c:16917 (gdb+0x8c228e)
    #22 objfile::lookup_symbol(block_enum, char const*, domain_enum) gdb/symfile-debug.c:288 (gdb+0xf39055)
    #23 lookup_symbol_via_quick_fns gdb/symtab.c:2385 (gdb+0xf66ab7)
    #24 lookup_symbol_in_objfile gdb/symtab.c:2516 (gdb+0xf6711b)
    #25 operator() gdb/symtab.c:2562 (gdb+0xf67272)
    #26 operator() gdb/../gdbsupport/function-view.h:305 (gdb+0xf776b1)
    #27 _FUN gdb/../gdbsupport/function-view.h:299 (gdb+0xf77708)
    #28 gdb::function_view<bool (objfile*)>::operator()(objfile*) const gdb/../gdbsupport/function-view.h:289 (gdb+0xc3fc97)
    #29 svr4_iterate_over_objfiles_in_search_order gdb/solib-svr4.c:3455 (gdb+0xecae47)
    #30 gdbarch_iterate_over_objfiles_in_search_order(gdbarch*, gdb::function_view<bool (objfile*)>, objfile*) gdb/gdbarch.c:5041 (gdb+0x537cad)
    #31 lookup_global_or_static_symbol gdb/symtab.c:2559 (gdb+0xf674fb)
    #32 lookup_global_symbol(char const*, block const*, domain_enum) gdb/symtab.c:2615 (gdb+0xf67780)
    #33 language_defn::lookup_symbol_nonlocal(char const*, block const*, domain_enum) const gdb/symtab.c:2447 (gdb+0xf66d6e)
    #34 lookup_symbol_aux gdb/symtab.c:2123 (gdb+0xf65cb3)
    #35 lookup_symbol_in_language(char const*, block const*, domain_enum, language, field_of_this_result*) gdb/symtab.c:1931 (gdb+0xf64dab)
    #36 set_initial_language() gdb/symfile.c:1708 (gdb+0xf43074)
    #37 symbol_file_add_main_1 gdb/symfile.c:1212 (gdb+0xf41608)
    #38 symbol_file_command(char const*, int) gdb/symfile.c:1681 (gdb+0xf42faf)
    #39 file_command gdb/exec.c:554 (gdb+0x94ff29)
    #40 do_simple_func gdb/cli/cli-decode.c:95 (gdb+0x6d9528)
    #41 cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735 (gdb+0x6e0f69)
    #42 execute_command(char const*, int) gdb/top.c:575 (gdb+0xff379c)
    #43 command_handler(char const*) gdb/event-top.c:552 (gdb+0x94b5bc)
    #44 command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:788 (gdb+0x94bc79)
    #45 tui_command_line_handler gdb/tui/tui-interp.c:104 (gdb+0x1034efc)
    #46 gdb_rl_callback_handler gdb/event-top.c:259 (gdb+0x94ab61)
    #47 rl_callback_read_char readline/readline/callback.c:290 (gdb+0x11be4ef)
    #48 gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195 (gdb+0x94a960)
    #49 gdb_rl_callback_read_char_wrapper gdb/event-top.c:234 (gdb+0x94aa21)
    #50 stdin_event_handler gdb/ui.c:155 (gdb+0x10751a0)
    #51 handle_file_event gdbsupport/event-loop.cc:573 (gdb+0x1d95bac)
    #52 gdb_wait_for_event gdbsupport/event-loop.cc:694 (gdb+0x1d962e4)
    #53 gdb_do_one_event(int) gdbsupport/event-loop.cc:264 (gdb+0x1d946d0)
    #54 start_event_loop gdb/main.c:412 (gdb+0xb5ab52)
    #55 captured_command_loop gdb/main.c:476 (gdb+0xb5ad41)
    #56 captured_main gdb/main.c:1320 (gdb+0xb5cec1)
    #57 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xb5cf70)
    #58 main gdb/gdb.c:32 (gdb+0x416776)

  Previous read of size 1 at 0x7b200000420d by thread T11:
    #0 write_gdbindex gdb/dwarf2/index-write.c:1229 (gdb+0x831630)
    bminor#1 write_dwarf_index(dwarf2_per_bfd*, char const*, char const*, char const*, dw_index_kind) gdb/dwarf2/index-write.c:1484 (gdb+0x832897)
    bminor#2 index_cache::store(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/index-cache.c:173 (gdb+0x82db8d)
    bminor#3 cooked_index::maybe_write_index(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/cooked-index.c:645 (gdb+0x7f1d49)
    bminor#4 operator() gdb/dwarf2/cooked-index.c:474 (gdb+0x7f0f31)
    bminor#5 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x7f2a13)
    bminor#6 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x700952)
    bminor#7 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x7381a0)
    bminor#8 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x737e91)
    bminor#9 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x737b59)
    bminor#10 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x738660)
    bminor#11 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x73825c)
    bminor#12 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x733623)
    #13 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x732bdf)
    #14 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x734c4f)
    #15 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x733bc5)
    #16 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x73300d)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x7330b2)
    #18 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x7330f2)
    #19 pthread_once <null> (libtsan.so.0+0x4457c)
    #20 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72f5dd)
    #21 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x733224)
    #22 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x732852)
    #23 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x737bef)
    #24 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x1dad25a)
    #25 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x1dacb7c)
    #26 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x1dadc2b)
    #27 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x1dad05c)
    #28 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x1db038e)
    #29 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x1db0319)
    #30 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x1db02ce)
    #31 <null> <null> (libstdc++.so.6+0xdcac2)
  ...
SUMMARY: ThreadSanitizer: data race gdb/dwarf2/read.c:21513 in dwarf2_per_cu_data::get_header() const
...

The race happens when issuing the "file $exec" command.

The race is between:
- a worker thread writing the index cache, and in the process reading
   dwarf2_per_cu_data::is_debug_type, and
- the main thread writing to dwarf2_per_cu_data::m_header_read_in.

The two bitfields dwarf2_per_cu_data::m_header_read_in and
dwarf2_per_cu_data::is_debug_type share the same bitfield container.

Fix this by making dwarf2_per_cu_data::m_header_read_in a packed<bool, 1>.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>

PR symtab/30392
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30392
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix data race on dwarf2_per_cu_data::{mark,is_debug_types}
38ef7c3 
With gdb build with -fsanitize=thread, and the exec from test-case
gdb.base/index-cache.exp, I run into:
...
$ rm -f ~/.cache/gdb/*; \
  gdb -q -batch -iex "set index-cache enabled on" index-cache \
    -ex "print foobar"
  ...
WARNING: ThreadSanitizer: data race (pid=23970)
  Write of size 1 at 0x7b200000410d by main thread:
    #0 dw_expand_symtabs_matching_file_matcher(dwarf2_per_objfile*, gdb::function_view<bool (char const*, bool)>) gdb/dwarf2/read.c:3077 (gdb+0x7ac54e)
    bminor#1 cooked_index_functions::expand_symtabs_matching(objfile*, gdb::function_view<bool (char const*, bool)>, lookup_name_info const*, gdb::function_view<bool (char const*)>, gdb::function_view<bool (compunit_symtab*)>, enum_flags<block_search_flag_values>, domain_enum, search_domain) gdb/dwarf2/read.c:16812 (gdb+0x7d039f)
    bminor#2 objfile::map_symtabs_matching_filename(char const*, char const*, gdb::function_view<bool (symtab*)>) gdb/symfile-debug.c:219 (gdb+0xda5aee)
    bminor#3 iterate_over_symtabs(char const*, gdb::function_view<bool (symtab*)>) gdb/symtab.c:648 (gdb+0xdc439d)
    bminor#4 lookup_symtab(char const*) gdb/symtab.c:662 (gdb+0xdc44a2)
    bminor#5 classify_name gdb/c-exp.y:3083 (gdb+0x61afec)
    bminor#6 c_yylex gdb/c-exp.y:3251 (gdb+0x61dd13)
    bminor#7 c_yyparse() build/gdb/c-exp.c.tmp:1988 (gdb+0x61f07e)
    bminor#8 c_parse(parser_state*) gdb/c-exp.y:3417 (gdb+0x62d864)
    bminor#9 language_defn::parser(parser_state*) const gdb/language.c:598 (gdb+0x9771c5)
    bminor#10 parse_exp_in_context gdb/parse.c:414 (gdb+0xb10a9b)
    bminor#11 parse_expression(char const*, innermost_block_tracker*, enum_flags<parser_flag>) gdb/parse.c:462 (gdb+0xb110ae)
    bminor#12 process_print_command_args gdb/printcmd.c:1321 (gdb+0xb4bf0c)
    #13 print_command_1 gdb/printcmd.c:1335 (gdb+0xb4ca2a)
    #14 print_command gdb/printcmd.c:1468 (gdb+0xb4cd5a)
    #15 do_simple_func gdb/cli/cli-decode.c:95 (gdb+0x65b078)
    #16 cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735 (gdb+0x65ed53)
    #17 execute_command(char const*, int) gdb/top.c:575 (gdb+0xe3a76a)
    #18 catch_command_errors gdb/main.c:518 (gdb+0xa1837d)
    #19 execute_cmdargs gdb/main.c:617 (gdb+0xa1853f)
    #20 captured_main_1 gdb/main.c:1289 (gdb+0xa1aa58)
    #21 captured_main gdb/main.c:1310 (gdb+0xa1b95a)
    #22 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xa1b95a)
    #23 main gdb/gdb.c:39 (gdb+0x42506a)

  Previous read of size 1 at 0x7b200000410d by thread T1:
    #0 write_gdbindex gdb/dwarf2/index-write.c:1214 (gdb+0x75bb30)
    bminor#1 write_dwarf_index(dwarf2_per_bfd*, char const*, char const*, char const*, dw_index_kind) gdb/dwarf2/index-write.c:1469 (gdb+0x75f803)
    bminor#2 index_cache::store(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/index-cache.c:173 (gdb+0x755a36)
    bminor#3 cooked_index::maybe_write_index(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/cooked-index.c:642 (gdb+0x71c96d)
    bminor#4 operator() gdb/dwarf2/cooked-index.c:471 (gdb+0x71c96d)
    bminor#5 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x71c96d)
    bminor#6 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x72a57c)
    bminor#7 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x72a5db)
    bminor#8 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x72a5db)
    bminor#9 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x72a5db)
    bminor#10 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x72a5db)
    bminor#11 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x72a5db)
    bminor#12 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x724954)
    #13 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x724954)
    #14 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x72434a)
    #15 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x72434a)
    #16 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x72434a)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x72434a)
    #18 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x72434a)
    #19 pthread_once <null> (libtsan.so.0+0x4457c)
    #20 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72532b)
    #21 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x72532b)
    #22 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x174568d)
    #23 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x174568d)
    #24 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x174568d)
    #25 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x174568d)
    #26 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x1748040)
    #27 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x1748040)
    #28 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x1748040)
    #29 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x1748040)
    #30 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x1748040)
    #31 <null> <null> (libstdc++.so.6+0xdcac2)
  ...
SUMMARY: ThreadSanitizer: data race gdb/dwarf2/read.c:3077 in dw_expand_symtabs_matching_file_matcher(dwarf2_per_objfile*, gdb::function_view<bool (char const*, bool)>)
...

The race happens when issuing the "file $exec" command.

The race is between:
- a worker thread writing the index cache, and in the process reading
  dwarf2_per_cu_data::is_debug_type, and
- the main thread writing to dwarf2_per_cu_data::mark.

The two bitfields dwarf2_per_cu_data::mark and
dwarf2_per_cu_data::is_debug_type share the same bitfield container.

Fix this by making dwarf2_per_cu_data::mark a packed<unsigned int, 1>.

Tested on x86_64-linux.

PR symtab/30718
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30718
Clownsw pushed a commit to Clownsw/binutils-gdb that referenced this pull request Sep 27, 2023
@vries
[gdb/symtab] Fix data race on dwarf2_per_cu_data::{files_read,is_debu…
0961970 
…g_types}

With gdb build with -fsanitize=thread, and the exec from test-case
gdb.base/index-cache.exp, I run into:
...
$ rm -f ~/.cache/gdb/*; \
  gdb -q -batch -iex "set index-cache enabled on" index-cache \
    -ex "print foobar"
  ...
WARNING: ThreadSanitizer: data race (pid=25018)
  Write of size 1 at 0x7b200000410d by main thread:
    #0 dw2_get_file_names_reader gdb/dwarf2/read.c:2033 (gdb+0x7ab023)
    bminor#1 dw2_get_file_names gdb/dwarf2/read.c:2130 (gdb+0x7ab023)
    bminor#2 dw_expand_symtabs_matching_file_matcher(dwarf2_per_objfile*, gdb::function_view<bool (char const*, bool)>) gdb/dwarf2/read.c:3105 (gdb+0x7ac6e9)
    bminor#3 cooked_index_functions::expand_symtabs_matching(objfile*, gdb::function_view<bool (char const*, bool)>, lookup_name_info const*, gdb::function_view<bool (char const*)>, gdb::function_view<bool (compunit_symtab*)>, enum_flags<block_search_flag_values>, domain_enum, search_domain) gdb/dwarf2/read.c:16812 (gdb+0x7d040f)
    bminor#4 objfile::map_symtabs_matching_filename(char const*, char const*, gdb::function_view<bool (symtab*)>) gdb/symfile-debug.c:219 (gdb+0xda5b6e)
    bminor#5 iterate_over_symtabs(char const*, gdb::function_view<bool (symtab*)>) gdb/symtab.c:648 (gdb+0xdc441d)
    bminor#6 lookup_symtab(char const*) gdb/symtab.c:662 (gdb+0xdc4522)
    bminor#7 classify_name gdb/c-exp.y:3083 (gdb+0x61afec)
    bminor#8 c_yylex gdb/c-exp.y:3251 (gdb+0x61dd13)
    bminor#9 c_yyparse() build/gdb/c-exp.c.tmp:1988 (gdb+0x61f07e)
    bminor#10 c_parse(parser_state*) gdb/c-exp.y:3417 (gdb+0x62d864)
    bminor#11 language_defn::parser(parser_state*) const gdb/language.c:598 (gdb+0x977245)
    bminor#12 parse_exp_in_context gdb/parse.c:414 (gdb+0xb10b1b)
    #13 parse_expression(char const*, innermost_block_tracker*, enum_flags<parser_flag>) gdb/parse.c:462 (gdb+0xb1112e)
    #14 process_print_command_args gdb/printcmd.c:1321 (gdb+0xb4bf8c)
    #15 print_command_1 gdb/printcmd.c:1335 (gdb+0xb4caaa)
    #16 print_command gdb/printcmd.c:1468 (gdb+0xb4cdda)
    #17 do_simple_func gdb/cli/cli-decode.c:95 (gdb+0x65b078)
    #18 cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735 (gdb+0x65ed53)
    #19 execute_command(char const*, int) gdb/top.c:575 (gdb+0xe3a7ea)
    #20 catch_command_errors gdb/main.c:518 (gdb+0xa183fd)
    #21 execute_cmdargs gdb/main.c:617 (gdb+0xa185bf)
    #22 captured_main_1 gdb/main.c:1289 (gdb+0xa1aad8)
    #23 captured_main gdb/main.c:1310 (gdb+0xa1b9da)
    #24 gdb_main(captured_main_args*) gdb/main.c:1339 (gdb+0xa1b9da)
    #25 main gdb/gdb.c:39 (gdb+0x42506a)

  Previous read of size 1 at 0x7b200000410d by thread T2:
    #0 write_gdbindex gdb/dwarf2/index-write.c:1214 (gdb+0x75bb30)
    bminor#1 write_dwarf_index(dwarf2_per_bfd*, char const*, char const*, char const*, dw_index_kind) gdb/dwarf2/index-write.c:1469 (gdb+0x75f803)
    bminor#2 index_cache::store(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/index-cache.c:173 (gdb+0x755a36)
    bminor#3 cooked_index::maybe_write_index(dwarf2_per_bfd*, index_cache_store_context const&) gdb/dwarf2/cooked-index.c:642 (gdb+0x71c96d)
    bminor#4 operator() gdb/dwarf2/cooked-index.c:471 (gdb+0x71c96d)
    bminor#5 _M_invoke /usr/include/c++/7/bits/std_function.h:316 (gdb+0x71c96d)
    bminor#6 std::function<void ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x72a57c)
    bminor#7 void std::__invoke_impl<void, std::function<void ()>&>(std::__invoke_other, std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:60 (gdb+0x72a5db)
    bminor#8 std::__invoke_result<std::function<void ()>&>::type std::__invoke<std::function<void ()>&>(std::function<void ()>&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x72a5db)
    bminor#9 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}::operator()() const /usr/include/c++/7/future:1421 (gdb+0x72a5db)
    bminor#10 std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void>::operator()() const /usr/include/c++/7/future:1362 (gdb+0x72a5db)
    bminor#11 std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<void>, std::__future_base::_Result_base::_Deleter>, std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run()::{lambda()bminor#1}, void> >::_M_invoke(std::_Any_data const&) /usr/include/c++/7/bits/std_function.h:302 (gdb+0x72a5db)
    bminor#12 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const /usr/include/c++/7/bits/std_function.h:706 (gdb+0x724954)
    #13 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*) /usr/include/c++/7/future:561 (gdb+0x724954)
    #14 void std::__invoke_impl<void, void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::__invoke_memfun_deref, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x72434a)
    #15 std::__invoke_result<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>::type std::__invoke<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x72434a)
    #16 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#1}::operator()() const /usr/include/c++/7/mutex:672 (gdb+0x72434a)
    #17 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::operator()() const /usr/include/c++/7/mutex:677 (gdb+0x72434a)
    #18 std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&)::{lambda()bminor#2}::_FUN() /usr/include/c++/7/mutex:677 (gdb+0x72434a)
    #19 pthread_once <null> (libtsan.so.0+0x4457c)
    #20 __gthread_once /usr/include/c++/7/x86_64-suse-linux/bits/gthr-default.h:699 (gdb+0x72532b)
    #21 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*>(std::once_flag&, void (std::__future_base::_State_baseV2::*&&)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*), std::__future_base::_State_baseV2*&&, std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*&&, bool*&&) /usr/include/c++/7/mutex:684 (gdb+0x72532b)
    #22 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool) /usr/include/c++/7/future:401 (gdb+0x174570d)
    #23 std::__future_base::_Task_state<std::function<void ()>, std::allocator<int>, void ()>::_M_run() /usr/include/c++/7/future:1423 (gdb+0x174570d)
    #24 std::packaged_task<void ()>::operator()() /usr/include/c++/7/future:1556 (gdb+0x174570d)
    #25 gdb::thread_pool::thread_function() gdbsupport/thread-pool.cc:242 (gdb+0x174570d)
    #26 void std::__invoke_impl<void, void (gdb::thread_pool::*)(), gdb::thread_pool*>(std::__invoke_memfun_deref, void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:73 (gdb+0x17480c0)
    #27 std::__invoke_result<void (gdb::thread_pool::*)(), gdb::thread_pool*>::type std::__invoke<void (gdb::thread_pool::*)(), gdb::thread_pool*>(void (gdb::thread_pool::*&&)(), gdb::thread_pool*&&) /usr/include/c++/7/bits/invoke.h:95 (gdb+0x17480c0)
    #28 decltype (__invoke((_S_declval<0ul>)(), (_S_declval<1ul>)())) std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::_M_invoke<0ul, 1ul>(std::_Index_tuple<0ul, 1ul>) /usr/include/c++/7/thread:234 (gdb+0x17480c0)
    #29 std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> >::operator()() /usr/include/c++/7/thread:243 (gdb+0x17480c0)
    #30 std::thread::_State_impl<std::thread::_Invoker<std::tuple<void (gdb::thread_pool::*)(), gdb::thread_pool*> > >::_M_run() /usr/include/c++/7/thread:186 (gdb+0x17480c0)
    #31 <null> <null> (libstdc++.so.6+0xdcac2)
  ...
SUMMARY: ThreadSanitizer: data race gdb/dwarf2/read.c:2033 in dw2_get_file_names_reader
...

The race happens when issuing the "file $exec" command.

The race is between:
- a worker thread writing the index cache, and in the process reading
  dwarf2_per_cu_data::is_debug_type, and
- the main thread writing to dwarf2_per_cu_data::files_read.

The two bitfields dwarf2_per_cu_data::files_read and
dwarf2_per_cu_data::is_debug_type share the same bitfield container.

Fix this by making dwarf2_per_cu_data::files_read a packed<bool, 1>.

Tested on x86_64-linux.

PR symtab/30718
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30718
berenm pushed a commit that referenced this pull request Sep 29, 2023
@T-J-Teru
gdb: use reopen_exec_file from reread_symbols
c7bdb38 
This commit fixes an issue that was discovered while writing the tests
for the previous commit.

I noticed that, when GDB restarts an inferior, the executable_changed
event would trigger twice.  The first notification would originate
from:

  #0  exec_file_attach (filename=0x4046680 "/tmp/hello.x", from_tty=0) at ../../src/gdb/exec.c:513
  #1  0x00000000006f3adb in reopen_exec_file () at ../../src/gdb/corefile.c:122
  #2  0x0000000000e6a3f2 in generic_mourn_inferior () at ../../src/gdb/target.c:3682
  #3  0x0000000000995121 in inf_child_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/inf-child.c:192
  #4  0x0000000000995cff in inf_ptrace_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/inf-ptrace.c:125
  #5  0x0000000000a32472 in linux_nat_target::mourn_inferior (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/linux-nat.c:3609
  #6  0x0000000000e68a40 in target_mourn_inferior (ptid=...) at ../../src/gdb/target.c:2761
  #7  0x0000000000a323ec in linux_nat_target::kill (this=0x2fe95c0 <the_amd64_linux_nat_target>) at ../../src/gdb/linux-nat.c:3593
  #8  0x0000000000e64d1c in target_kill () at ../../src/gdb/target.c:924
  #9  0x00000000009a19bc in kill_if_already_running (from_tty=1) at ../../src/gdb/infcmd.c:328
  #10 0x00000000009a1a6f in run_command_1 (args=0x0, from_tty=1, run_how=RUN_STOP_AT_MAIN) at ../../src/gdb/infcmd.c:381
  #11 0x00000000009a20a5 in start_command (args=0x0, from_tty=1) at ../../src/gdb/infcmd.c:527
  #12 0x000000000068dc5d in do_simple_func (args=0x0, from_tty=1, c=0x35c7200) at ../../src/gdb/cli/cli-decode.c:95

While the second originates from:

  #0  exec_file_attach (filename=0x3d7a1d0 "/tmp/hello.x", from_tty=0) at ../../src/gdb/exec.c:513
  #1  0x0000000000dfe525 in reread_symbols (from_tty=1) at ../../src/gdb/symfile.c:2517
  #2  0x00000000009a1a98 in run_command_1 (args=0x0, from_tty=1, run_how=RUN_STOP_AT_MAIN) at ../../src/gdb/infcmd.c:398
  #3  0x00000000009a20a5 in start_command (args=0x0, from_tty=1) at ../../src/gdb/infcmd.c:527
  #4  0x000000000068dc5d in do_simple_func (args=0x0, from_tty=1, c=0x35c7200) at ../../src/gdb/cli/cli-decode.c:95

In the first case the call to exec_file_attach first passes through
reopen_exec_file.  The reopen_exec_file performs a modification time
check on the executable file, and only calls exec_file_attach if the
executable has changed on disk since it was last loaded.

However, in the second case things work a little differently.  In this
case GDB is really trying to reread the debug symbol.  As such, we
iterate over the objfiles list, and for each of those we check the
modification time, if the file on disk has changed then we reload the
debug symbols from that file.

However, there is an additional check, if the objfile has the same
name as the executable then we will call exec_file_attach, but we do
so without checking the cached modification time that indicates when
the executable was last reloaded, as a result, we reload the
executable twice.

In this commit I propose that reread_symbols be changed to
unconditionally call reopen_exec_file before performing the objfile
iteration.  This will ensure that, if the executable has changed, then
the executable will be reloaded, however, if the executable has
already been recently reloaded, we will not reload it for a second
time.

After handling the executable, GDB can then iterate over the objfiles
list and reload them in the normal way.

With this done I now see the executable reloaded only once when GDB
restarts an inferior, which means I can remove the kfail that I added
to the gdb.python/py-exec-file.exp test in the previous commit.

Approved-By: Tom Tromey <tom@tromey.com>
berenm pushed a commit that referenced this pull request Oct 6, 2023
@T-J-Teru @simark
gdb: fix auxv cache clearing from new_objfile observer
1b28c0f 
It was pointed out on the mailing list that a recently added
test (gdb.python/py-progspace-events.exp) was failing when run with
the native-extended-gdbserver board.  This test was added with this
commit:

  commit 59912fb
  Date:   Tue Sep 19 11:45:36 2023 +0100

      gdb: add Python events for program space addition and removal

It turns out though that the test is failing due to a existing bug
in GDB, the new test just exposes the problem.  Additionally, the
failure really doesn't even rely on the new functionality added in the
above commit.  I reduced the test to a simple set of steps that
reproduced the failure and tested against GDB 13, and the test passes;
so the bug was introduced since then.  In fact, the bug was introduced
with this commit:

  commit a282736
  Date:   Fri Sep 8 15:48:16 2023 +0100

      gdb: remove final user of the executable_changed observer

This commit changed how the per-inferior auxv data cache is managed,
specifically, when the cache is cleared, and it is this that leads to
the failure.

This bug is interesting because it exposes a number of issues with
GDB, I'll explain all of the problems I see, though ultimately, I only
propose fixing one problem in this commit, which is enough to resolve
the crash we are currently seeing.

The crash that we are seeing manifests like this:

  ...
  [Inferior 2 (process 3970384) exited normally]
  +inferior 1
  [Switching to inferior 1 [process 3970383] (/tmp/build/gdb/testsuite/outputs/gdb.python/py-progspace-events/py-progspace-events)]
  [Switching to thread 1.1 (Thread 3970383.3970383)]
  #0  breakpt () at /tmp/build/gdb/testsuite/../../../src/gdb/testsuite/gdb.python/py-progspace-events.c:28
  28	{ /* Nothing.  */ }
  (gdb) step
  +step
  terminate called after throwing an instance of 'gdb_exception_error'

  Fatal signal: Aborted
  ... etc ...

What's happening is that GDB attempts to refill the auxv cache as a
result of the gdbarch_has_shared_address_space call in
program_space::~program_space, the backtrace looks like this:

  #0  0x00007fb4f419a9a5 in raise () from /lib64/libpthread.so.0
  #1  0x00000000008b635d in handle_fatal_signal (sig=6) at ../../src/gdb/event-top.c:912
  #2  <signal handler called>
  #3  0x00007fb4f38e3625 in raise () from /lib64/libc.so.6
  #4  0x00007fb4f38cc8d9 in abort () from /lib64/libc.so.6
  #5  0x00007fb4f3c70756 in __gnu_cxx::__verbose_terminate_handler() [clone .cold] () from /lib64/libstdc++.so.6
  #6  0x00007fb4f3c7c6dc in __cxxabiv1::__terminate(void (*)()) () from /lib64/libstdc++.so.6
  #7  0x00007fb4f3c7b6e9 in __cxa_call_terminate () from /lib64/libstdc++.so.6
  #8  0x00007fb4f3c7c094 in __gxx_personality_v0 () from /lib64/libstdc++.so.6
  #9  0x00007fb4f3a80c63 in _Unwind_RaiseException_Phase2 () from /lib64/libgcc_s.so.1
  #10 0x00007fb4f3a8154e in _Unwind_Resume () from /lib64/libgcc_s.so.1
  #11 0x0000000000e8832d in target_read_alloc_1<unsigned char> (ops=0x408a3a0, object=TARGET_OBJECT_AUXV, annex=0x0) at ../../src/gdb/target.c:2266
  #12 0x0000000000e73dea in target_read_alloc (ops=0x408a3a0, object=TARGET_OBJECT_AUXV, annex=0x0) at ../../src/gdb/target.c:2315
  #13 0x000000000058248c in target_read_auxv_raw (ops=0x408a3a0) at ../../src/gdb/auxv.c:379
  #14 0x000000000058243d in target_read_auxv () at ../../src/gdb/auxv.c:368
  #15 0x000000000058255c in target_auxv_search (match=0x0, valp=0x7ffdee17c598) at ../../src/gdb/auxv.c:415
  #16 0x0000000000a464bb in linux_is_uclinux () at ../../src/gdb/linux-tdep.c:433
  #17 0x0000000000a464f6 in linux_has_shared_address_space (gdbarch=0x409a2d0) at ../../src/gdb/linux-tdep.c:440
  #18 0x0000000000510eae in gdbarch_has_shared_address_space (gdbarch=0x409a2d0) at ../../src/gdb/gdbarch.c:4889
  #19 0x0000000000bc7558 in program_space::~program_space (this=0x4544aa0, __in_chrg=<optimized out>) at ../../src/gdb/progspace.c:124
  #20 0x00000000009b245d in delete_inferior (inf=0x47b3de0) at ../../src/gdb/inferior.c:290
  #21 0x00000000009b2c10 in prune_inferiors () at ../../src/gdb/inferior.c:480
  #22 0x00000000009c5e3e in fetch_inferior_event () at ../../src/gdb/infrun.c:4558
  #23 0x000000000099b4dc in inferior_event_handler (event_type=INF_REG_EVENT) at ../../src/gdb/inf-loop.c:42
  #24 0x0000000000cbc64f in remote_async_serial_handler (scb=0x4090a30, context=0x408a6b0) at ../../src/gdb/remote.c:14859
  #25 0x0000000000d83d3a in run_async_handler_and_reschedule (scb=0x4090a30) at ../../src/gdb/ser-base.c:138
  #26 0x0000000000d83e1f in fd_event (error=0, context=0x4090a30) at ../../src/gdb/ser-base.c:189

So this is problem #1, if we throw an exception while deleting a
program_space then this is not caught, and is going to crash GDB.

Problem #2 becomes evident when we ask why GDB is throwing an error in
this case; the error is thrown because the remote target, operating in
non-async mode, can't read the auxv data while an inferior is running
and GDB is waiting for a stop reply.  The problem here then, is why
does GDB get into a position where it tries to interact with the
remote target in this way, at this time?  The problem is caused by the
prune_inferiors call which can be seen in the above backtrace.

In prune_inferiors we check if the inferior is deletable, and if it
is, we delete it.  The problem is, I think, we should also check if
the target is currently in a state that would allow us to delete the
inferior.  We don't currently have such a check available, we'd need
to add one, but for the remote target, this would return false if the
remote is in async mode and the remote is currently waiting for a stop
reply.  With this change in place GDB would defer deleting the
inferior until the remote target has stopped, at which point GDB would
be able to refill the auxv cache successfully.

And then, problem #3 becomes evident when we ask why GDB is needing to
refill the auxv cache now when it didn't need to for GDB 13.  This is
where the second commit mentioned above (a282736) comes in.
Prior to this commit, the auxv cache was cleared by the
executable_changed observer, while after that commit the auxv cache
was cleared by the new_objfile observer -- but only when the
new_objfile observer is used in the special mode that actually means
that all objfiles have been unloaded (I know, the overloading of the
new_objfile observer is horrible, and unnecessary, but it's not really
important for this bug).

The difference arises because the new_objfile observer is triggered
from clear_symtab_users, which in turn is called from
program_space::~program_space.  The new_objfile observer for auxv does
this:

  static void
  auxv_new_objfile_observer (struct objfile *objfile)
  {
    if (objfile == nullptr)
      invalidate_auxv_cache_inf (current_inferior ());
  }

That is, when all the objfiles are unloaded, we clear the auxv cache
for the current inferior.

The problem is, then when we look at the prune_inferiors ->
delete_inferior -> ~program_space path, we see that the current
inferior is not going to be an inferior that exists within the
program_space being deleted; delete_inferior removes the deleted
inferior from the global inferior list, and then only deletes the
program_space if program_space::empty() returns true, which is only
the case if the current inferior isn't within the program_space to
delete, and no other inferior exists within that program_space
either.

What this means is that when the new_objfile observer is called we
can't rely on the current inferior having any relationship with the
program space in which the objfiles were removed.  This was an error
in the commit a282736, the only thing we can rely on is the
current program space.  As a result of this mistake, after commit
a282736, GDB was sometimes clearing the auxv cache for a random
inferior.  In the native target case this was harmless as we can
always refill the cache when needed, but in the remote target case, if
we need to refill the cache when the remote target is executing, then
we get the crash we observed.

And additionally, if we think about this a little more, we see that
commit a282736 made another mistake.  When all the objfiles are
removed, they are removed from a program_space, a program_space might
contain multiple inferiors, so surely, we should clear the auxv cache
for all of the matching inferiors?

Given these two insights, that the current_inferior is not relevant,
only the current_program_space, and that we should be clearing the
cache for all inferiors in the current_program_space, we can update
auxv_new_objfile_observer to:

  if (objfile == nullptr)
    {
      for (inferior *inf : all_inferiors ())
	{
	  if (inf->pspace == current_program_space)
	    invalidate_auxv_cache_inf (inf);
	}
    }

With this change we now correctly clear the auxv cache for the correct
inferiors, and GDB no longer needs to refill the cache at an
inconvenient time, this avoids the crash we were seeing.

And finally, we reach problem #4.  Inspired by the observation that
using the current_inferior from within the ~program_space function was
not correct, I added some debug to see if current_inferior() was
called anywhere else (below ~program_space), and the answer is yes,
it's called a often.  Mostly the culprit is GDB doing:

  current_inferior ()->top_target ()-> ....

But I think all of these calls are most likely doing the wrong thing,
and only work because the top target in all these cases is shared
between all inferiors, e.g. it's the native target, or the remote
target for all inferiors.  But if we had a truly multi-connection
setup, then we might start to see odd behaviour.

Problem #1 I'm just ignoring for now, I guess at some point we might
run into this again, and then we'd need to solve this.  But in this
case I wasn't sure what a "good" solution would look like.  We need
the auxv data in order to implement the linux_is_uclinux() function.
If we can't get the auxv data then what should we do, assume yes, or
assume no?  The right answer would probably be to propagate the error
back up the stack, but then we reach ~program_space, and throwing
exceptions from a destructor is problematic, so we'd need to catch and
deal at this point.  The linux_is_uclinux() call is made from within
gdbarch_has_shared_address_space(), which is used like:

  if (!gdbarch_has_shared_address_space (target_gdbarch ()))
    delete this->aspace;

So, we would have to choose; delete the address space or not.  If we
delete it on error, then we might delete an address space that is
shared within another program space.  If we don't delete the address
space, then we might leak it.  Neither choice is great.

A better solution might be to have the address spaces be reference
counted, then we could remove the gdbarch_has_shared_address_space
call completely, and just rely on the reference count to auto-delete
the address space when appropriate.

The solution for problem #2 I already hinted at above, we should have
a new target_can_delete_inferiors() call, which should be called from
prune_inferiors, this would prevent GDB from trying to delete
inferiors when a (remote) target is in a state where we know it can't
delete the inferior.  Deleting an inferior often (always?) requires
sending packets to the remote, and if the remote is waiting for a stop
reply then this will never work, so the pruning should be deferred in
this case.

The solution for problem #3 is included in this commit.

And, for problem #4, I'm not sure what the right solution is.  Maybe
delete_inferior should ensure the inferior to be deleted is in place
when ~program_space is called?  But that seems a little weird, as the
current inferior would, in theory, still be using the current
program_space...

Anyway, after this commit, the gdb.python/py-progspace-events.exp test
now passes when run with the native-extended-remote board.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30935
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I41f0e6e2d7ecc1e5e55ec170f37acd4052f46eaf
migthymax referenced this pull request in AmigaLabs/binutils-gdb Oct 10, 2023
@migthymax
Merge pull request #9 from migthymax/2-default-behavior-of-strip-caus…
7afeb90 
…e-error-symbol-xxxxxx-required-but-not-present-while-adtoolss-default-behavior-of-strip-works

2 default behavior of strip cause error symbol xxxxxx required but not present while adtoolss default behavior of strip works
berenm pushed a commit that referenced this pull request Nov 14, 2023
@palves
stop_all_threads: (re-)enable async before waiting for stops
d828dbe 
Running the
gdb.threads/step-over-thread-exit-while-stop-all-threads.exp testcase
added later in the series against gdbserver, after the
TARGET_WAITKIND_NO_RESUMED fix from the following patch, would run
into an infinite loop in stop_all_threads, leading to a timeout:

  FAIL: gdb.threads/step-over-thread-exit-while-stop-all-threads.exp: displaced-stepping=off: target-non-stop=on: iter 0: continue (timeout)

The is really a latent bug, and it is about the fact that
stop_all_threads stops listening to events from a target as soon as it
sees a TARGET_WAITKIND_NO_RESUMED, ignoring that
TARGET_WAITKIND_NO_RESUMED may be delayed.  handle_no_resumed knows
how to handle delayed no-resumed events, but stop_all_threads was
never taught to.

In more detail, here's what happens with that testcase:

#1 - Multiple threads report breakpoint hits to gdb.

#2 - gdb picks one events, and it's for thread 1.  All other stops are
     left pending.  thread 1 needs to move past a breakpoint, so gdb
     stops all threads to start an inline step over for thread 1.
     While stopping threads, some of the threads that were still
     running report events that are also left pending.

#2 - gdb steps thread 1

#3 - Thread 1 exits while stepping (it steps over an exit syscall),
     gdbserver reports thread exit for thread 1

#4 - Thread 1 was the last resumed thread, so gdbserver also reports
     no-resumed:

    [remote]   Notification received: Stop:w0;p3445d0.3445d3
    [remote] Sending packet: $vStopped#55
    [remote] Packet received: N
    [remote] Sending packet: $vStopped#55
    [remote] Packet received: OK

#5 - gdb processes the thread exit for thread 1, finishes the step
     over and restarts threads.

#6 - gdb picks the next event to process out of one of the resumed
     threads with pending events:

    [infrun] random_resumed_with_pending_wait_status: Found 32 events, selecting #11

#7 - This is again a breakpoint hit and the breakpoint needs to be
     stepped over too, so gdb starts a step-over dance again.

#8 - We reach stop_all_threads, which finds that some threads need to
     be stopped.

#9 - wait_one finally consumes the no-resumed event queue by #4.
     Seeing this, wait_one disable target async, to stop listening for
     events out of the remote target.

#10 - We still haven't seen all the stops expected, so
      stop_all_threads tries another iteration.

#11 - Because the remote target is no longer async, and there are no
      other targets, wait_one return no-resumed immediately without
      polling the remote target.

#12 - We still haven't seen all the stops expected, so
      stop_all_threads tries another iteration.  goto #11, looping
      forever.

Fix this by explicitly enabling/re-enabling target async on targets
that can async, before waiting for stops.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>
Change-Id: Ie3ffb0df89635585a6631aa842689cecc989e33f
berenm pushed a commit that referenced this pull request Dec 4, 2023
@KevinBuettner @T-J-Teru
Fix detach bug when lwp has exited/terminated
57e6a09 
When using GDB on native linux, it can happen that, while attempting
to detach an inferior, the inferior may have been exited or have been
killed, yet still be in the list of lwps.  Should that happen, the
assert in x86_linux_update_debug_registers in
gdb/nat/x86-linux-dregs.c will trigger.  The line in question looks
like this:

  gdb_assert (lwp_is_stopped (lwp));

For this case, the lwp isn't stopped - it's dead.

The bug which brought this problem to my attention is one in which the
pwntools library uses GDB to to debug a process; as the script is
shutting things down, it kills the process that GDB is debugging and
also sends GDB a SIGTERM signal, which causes GDB to detach all
inferiors prior to exiting.  Here's a link to the bug:

https://bugzilla.redhat.com/show_bug.cgi?id=2192169

The following shell command mimics part of what the pwntools
reproducer script does (with regard to shutting things down), but
reproduces the bug much less reliably.  I have found it necessary to
run the command a bunch of times before seeing the bug.  (I usually
see it within 5-10 repetitions.)  If you choose to try this command,
make sure that you have no running "cat" or "gdb" processes first!

  cat </dev/zero >/dev/null & \
  (sleep 5; (kill -KILL `pgrep cat` & kill -TERM `pgrep gdb`)) & \
  sleep 1 ; \
  gdb -q -iex 'set debuginfod enabled off' -ex 'set height 0' \
      -ex c /usr/bin/cat `pgrep cat`

So, basically, the idea here is to kill both gdb and cat at roughly
the same time.  If we happen to attempt the detach before the process
lwp has been deleted from GDB's (linux native) LWP data structures,
then the assert will trigger.  The relevant part of the backtrace
looks like this:

  #8  0x00000000008a83ae in x86_linux_update_debug_registers (lwp=0x1873280)
      at gdb/nat/x86-linux-dregs.c:146
  #9  0x00000000008a862f in x86_linux_prepare_to_resume (lwp=0x1873280)
      at gdb/nat/x86-linux.c:81
  #10 0x000000000048ea42 in x86_linux_nat_target::low_prepare_to_resume (
      this=0x121eee0 <the_amd64_linux_nat_target>, lwp=0x1873280)
      at gdb/x86-linux-nat.h:70
  #11 0x000000000081a452 in detach_one_lwp (lp=0x1873280, signo_p=0x7fff8ca3441c)
      at gdb/linux-nat.c:1374
  #12 0x000000000081a85f in linux_nat_target::detach (
      this=0x121eee0 <the_amd64_linux_nat_target>, inf=0x16e8f70, from_tty=0)
      at gdb/linux-nat.c:1450
  #13 0x000000000083a23b in thread_db_target::detach (
      this=0x1206ae0 <the_thread_db_target>, inf=0x16e8f70, from_tty=0)
      at gdb/linux-thread-db.c:1385
  #14 0x0000000000a66722 in target_detach (inf=0x16e8f70, from_tty=0)
      at gdb/target.c:2526
  #15 0x0000000000a8f0ad in kill_or_detach (inf=0x16e8f70, from_tty=0)
      at gdb/top.c:1659
  #16 0x0000000000a8f4fa in quit_force (exit_arg=0x0, from_tty=0)
      at gdb/top.c:1762
  #17 0x000000000070829c in async_sigterm_handler (arg=0x0)
      at gdb/event-top.c:1141

My colleague, Andrew Burgess, has done some recent work on other
problems with detach.  Upon hearing of this problem, he came up a test
case which reliably reproduces the problem and tests for a few other
problems as well.  In addition to testing detach when the inferior has
terminated due to a signal, it also tests detach when the inferior has
exited normally.  Andrew observed that the linux-native-only
"checkpoint" command would be affected too, so the test also tests
those cases when there's an active checkpoint.

For the LWP exit / termination case with no checkpoint, that's handled
via newly added checks of the waitstatus in detach_one_lwp in
linux-nat.c.

For the checkpoint detach problem, I chose to pass the lwp_info
to linux_fork_detach in linux-fork.c.  With that in place, suitable
tests were added before attempting a PTRACE_DETACH operation.

I added a few asserts at the beginning of linux_fork_detach and
modified the caller code so that the newly added asserts shouldn't
trigger.  (That's what the 'pid == inferior_ptid.pid' check is about
in gdb/linux-nat.c.)

Lastly, I'll note that the checkpoint code needs some work with regard
to background execution.  This patch doesn't attempt to fix that
problem, but it doesn't make it any worse.  It does slightly improve
the situation with detach because, due to the check noted above,
linux_fork_detach() won't be called for the wrong inferior when there
are multiple inferiors.  (There are at least two other problems with
the checkpoint code when there are multiple inferiors.  See:
https://sourceware.org/bugzilla/show_bug.cgi?id=31065)

This commit also adds a new test,
gdb.base/process-dies-while-detaching.exp.  Andrew Burgess is the
primary author of this test case.  Its design is similar to that of
gdb.threads/main-thread-exit-during-detach.exp, which was also written
by Andrew.

This test checks that GDB correctly handles several cases that can
occur when GDB attempts to detach an inferior process.  The process
can exit or be terminated (e.g.  via SIGKILL) prior to GDB's event
loop getting a chance to remove it from GDB's internal data
structures.  To complicate things even more, detach works differently
when a checkpoint (created via GDB's "checkpoint" command) exists for
the inferior.  This test checks all four possibilities: process exit
with no checkpoint, process termination with no checkpoint, process
exit with a checkpoint, and process termination with a checkpoint.

Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Approved-By: Andrew Burgess <aburgess@redhat.com>
berenm pushed a commit that referenced this pull request Feb 13, 2024
@vries
[gdb/dap] Catch and log exceptions in dap threads
433ae2c 
When running test-case gdb.dap/eof.exp, it occasionally coredumps.

The thread triggering the coredump is:
...
 #0  0x0000ffff42bb2280 in __pthread_kill_implementation () from /lib64/libc.so.6
 #1  0x0000ffff42b65800 [PAC] in raise () from /lib64/libc.so.6
 #2  0x00000000007b03e8 [PAC] in handle_fatal_signal (sig=11)
     at gdb/event-top.c:926
 #3  0x00000000007b0470 in handle_sigsegv (sig=11)
     at gdb/event-top.c:976
 #4  <signal handler called>
 #5  0x0000000000606080 in cli_ui_out::do_message (this=0xffff2f7ed728, style=...,
     format=0xffff0c002af1 "%s", args=...) at gdb/cli-out.c:232
 #6  0x0000000000ce6358 in ui_out::call_do_message (this=0xffff2f7ed728, style=...,
     format=0xffff0c002af1 "%s") at gdb/ui-out.c:584
 #7  0x0000000000ce6610 in ui_out::vmessage (this=0xffff2f7ed728, in_style=...,
     format=0x16f93ea "", args=...) at gdb/ui-out.c:621
 #8  0x0000000000ce3a9c in ui_file::vprintf (this=0xfffffbea1b18, ...)
     at gdb/ui-file.c:74
 #9  0x0000000000d2b148 in gdb_vprintf (stream=0xfffffbea1b18, format=0x16f93e8 "%s",
     args=...) at gdb/utils.c:1898
 #10 0x0000000000d2b23c in gdb_printf (stream=0xfffffbea1b18, format=0x16f93e8 "%s")
     at gdb/utils.c:1913
 #11 0x0000000000ab5208 in gdbpy_write (self=0x33fe35d0, args=0x342ec280, kw=0x345c08b0)
     at gdb/python/python.c:1464
 #12 0x0000ffff434acedc in cfunction_call () from /lib64/libpython3.12.so.1.0
 #13 0x0000ffff4347c500 [PAC] in _PyObject_MakeTpCall ()
     from /lib64/libpython3.12.so.1.0
 #14 0x0000ffff43488b64 [PAC] in _PyEval_EvalFrameDefault ()
    from /lib64/libpython3.12.so.1.0
 #15 0x0000ffff434d8cd0 [PAC] in method_vectorcall () from /lib64/libpython3.12.so.1.0
 #16 0x0000ffff434b9824 [PAC] in PyObject_CallOneArg () from /lib64/libpython3.12.so.1.0
 #17 0x0000ffff43557674 [PAC] in PyFile_WriteObject () from /lib64/libpython3.12.so.1.0
 #18 0x0000ffff435577a0 [PAC] in PyFile_WriteString () from /lib64/libpython3.12.so.1.0
 #19 0x0000ffff43465354 [PAC] in thread_excepthook () from /lib64/libpython3.12.so.1.0
 #20 0x0000ffff434ac6e0 [PAC] in cfunction_vectorcall_O ()
    from /lib64/libpython3.12.so.1.0
 #21 0x0000ffff434a32d8 [PAC] in PyObject_Vectorcall () from /lib64/libpython3.12.so.1.0
 #22 0x0000ffff43488b64 [PAC] in _PyEval_EvalFrameDefault ()
    from /lib64/libpython3.12.so.1.0
 #23 0x0000ffff434d8d88 [PAC] in method_vectorcall () from /lib64/libpython3.12.so.1.0
 #24 0x0000ffff435e0ef4 [PAC] in thread_run () from /lib64/libpython3.12.so.1.0
 #25 0x0000ffff43591ec0 [PAC] in pythread_wrapper () from /lib64/libpython3.12.so.1.0
 #26 0x0000ffff42bb0584 [PAC] in start_thread () from /lib64/libc.so.6
 #27 0x0000ffff42c1fd4c [PAC] in thread_start () from /lib64/libc.so.6
...

The direct cause for the coredump seems to be that cli_ui_out::do_message
is trying to write to a stream variable which does not look sound:
...
(gdb) p *stream
$8 = {_vptr.ui_file = 0x0, m_applied_style = {m_foreground = {m_simple = true, {
        m_value = 0, {m_red = 0 '\000', m_green = 0 '\000', m_blue = 0 '\000'}}},
    m_background = {m_simple = 32, {m_value = 65535, {m_red = 255 '\377',
          m_green = 255 '\377', m_blue = 0 '\000'}}},
    m_intensity = (unknown: 0x438fe710), m_reverse = 255}}
...

The string that is being printed is:
...
(gdb) p str
$9 = "Exception in thread "
...
so AFAICT this is a DAP thread running into an exception and trying to print
it.

If we look at the state of gdb's main thread, we have:
...
 #0  0x0000ffff42bac914 in __futex_abstimed_wait_cancelable64 () from /lib64/libc.so.6
 #1  0x0000ffff42bafb44 [PAC] in pthread_cond_timedwait@@GLIBC_2.17 ()
    from /lib64/libc.so.6
 #2  0x0000ffff43466e9c [PAC] in take_gil () from /lib64/libpython3.12.so.1.0
 #3  0x0000ffff43484fe0 [PAC] in PyEval_RestoreThread ()
     from /lib64/libpython3.12.so.1.0
 #4  0x0000000000ab8698 [PAC] in gdbpy_allow_threads::~gdbpy_allow_threads (
     this=0xfffffbea1cf8, __in_chrg=<optimized out>)
     at gdb/python/python-internal.h:769
 #5  0x0000000000ab2fec in execute_gdb_command (self=0x33fe35d0, args=0x34297b60,
     kw=0x34553d20) at gdb/python/python.c:681
 #6  0x0000ffff434acedc in cfunction_call () from /lib64/libpython3.12.so.1.0
 #7  0x0000ffff4347c500 [PAC] in _PyObject_MakeTpCall ()
     from /lib64/libpython3.12.so.1.0
 #8  0x0000ffff43488b64 [PAC] in _PyEval_EvalFrameDefault ()
    from /lib64/libpython3.12.so.1.0
 #9  0x0000ffff4353bce8 [PAC] in _PyObject_VectorcallTstate.lto_priv.3 ()
    from /lib64/libpython3.12.so.1.0
 #10 0x0000000000ab87fc [PAC] in gdbpy_event::operator() (this=0xffff14005900)
     at gdb/python/python.c:1061
 #11 0x0000000000ab93e8 in std::__invoke_impl<void, gdbpy_event&> (__f=...)
     at /usr/include/c++/13/bits/invoke.h:61
 #12 0x0000000000ab9204 in std::__invoke_r<void, gdbpy_event&> (__fn=...)
     at /usr/include/c++/13/bits/invoke.h:111
 #13 0x0000000000ab8e90 in std::_Function_handler<..>::_M_invoke(...) (...)
     at /usr/include/c++/13/bits/std_function.h:290
 #14 0x000000000062e0d0 in std::function<void ()>::operator()() const (
     this=0xffff14005830) at /usr/include/c++/13/bits/std_function.h:591
 #15 0x0000000000b67f14 in run_events (error=0, client_data=0x0)
     at gdb/run-on-main-thread.c:76
 #16 0x000000000157e290 in handle_file_event (file_ptr=0x33dae3a0, ready_mask=1)
     at gdbsupport/event-loop.cc:573
 #17 0x000000000157e760 in gdb_wait_for_event (block=1)
     at gdbsupport/event-loop.cc:694
 #18 0x000000000157d464 in gdb_do_one_event (mstimeout=-1)
     at gdbsupport/event-loop.cc:264
 #19 0x0000000000943a84 in start_event_loop () at gdb/main.c:401
 #20 0x0000000000943bfc in captured_command_loop () at gdb/main.c:465
 #21 0x000000000094567c in captured_main (data=0xfffffbea23e8)
     at gdb/main.c:1335
 #22 0x0000000000945700 in gdb_main (args=0xfffffbea23e8)
     at gdb/main.c:1354
 #23 0x0000000000423ab4 in main (argc=14, argv=0xfffffbea2578)
     at gdb/gdb.c:39
...

AFAIU, there's a race between the two threads on gdb_stderr:
- the DAP thread samples the gdb_stderr value, and uses it a bit later to
  print to
- the gdb main thread changes the gdb_stderr value forth and back,
  using a temporary value for string capture purposes

The non-sound stream value is caused by gdb_stderr being sampled while
pointing to a str_file object, and used once the str_file object is already
destroyed.

The error here is that the DAP thread attempts to print to gdb_stderr.

Fix this by adding a thread_wrapper that:
- catches all exceptions and logs them to dap.log, and
- while we're at it, logs when exiting
and using the thread_wrapper for each DAP thread.

Tested on aarch64-linux.

Approved-By: Tom Tromey <tom@tromey.com>
berenm pushed a commit that referenced this pull request Feb 15, 2024
@vries
[gdb/dap] Fix exit race
98e1896 
When running test-case gdb.dap/eof.exp, we're likely to get a coredump due to
a segfault in new_threadstate.

At the point of the core dump, the gdb main thread looks like:
...
 (gdb) bt
 #0  0x0000fffee30d2280 in __pthread_kill_implementation () from /lib64/libc.so.6
 #1  0x0000fffee3085800 [PAC] in raise () from /lib64/libc.so.6
 #2  0x00000000007b03e8 [PAC] in handle_fatal_signal (sig=11)
     at gdb/event-top.c:926
 #3  0x00000000007b0470 in handle_sigsegv (sig=11)
     at gdb/event-top.c:976
 #4  <signal handler called>
 #5  0x0000fffee3a4db14 in new_threadstate () from /lib64/libpython3.12.so.1.0
 #6  0x0000fffee3ab0548 [PAC] in PyGILState_Ensure () from /lib64/libpython3.12.so.1.0
 #7  0x0000000000a6d034 [PAC] in gdbpy_gil::gdbpy_gil (this=0xffffcb279738)
     at gdb/python/python-internal.h:787
 #8  0x0000000000ab87ac in gdbpy_event::~gdbpy_event (this=0xfffea8001ee0,
     __in_chrg=<optimized out>) at gdb/python/python.c:1051
 #9  0x0000000000ab9460 in std::_Function_base::_Base_manager<...>::_M_destroy
     (__victim=...) at /usr/include/c++/13/bits/std_function.h:175
 #10 0x0000000000ab92dc in std::_Function_base::_Base_manager<...>::_M_manager
     (__dest=..., __source=..., __op=std::__destroy_functor)
     at /usr/include/c++/13/bits/std_function.h:203
 #11 0x0000000000ab8f14 in std::_Function_handler<...>::_M_manager(...) (...)
     at /usr/include/c++/13/bits/std_function.h:282
 #12 0x000000000042dd9c in std::_Function_base::~_Function_base (this=0xfffea8001c10,
     __in_chrg=<optimized out>) at /usr/include/c++/13/bits/std_function.h:244
 #13 0x000000000042e654 in std::function<void ()>::~function() (this=0xfffea8001c10,
     __in_chrg=<optimized out>) at /usr/include/c++/13/bits/std_function.h:334
 #14 0x0000000000b68e60 in std::_Destroy<std::function<void ()> >(...) (...)
     at /usr/include/c++/13/bits/stl_construct.h:151
 #15 0x0000000000b68cd0 in std::_Destroy_aux<false>::__destroy<...>(...) (...)
     at /usr/include/c++/13/bits/stl_construct.h:163
 #16 0x0000000000b689d8 in std::_Destroy<...>(...) (...)
     at /usr/include/c++/13/bits/stl_construct.h:196
 #17 0x0000000000b68414 in std::_Destroy<...>(...) (...)
     at /usr/include/c++/13/bits/alloc_traits.h:948
 #18 std::vector<...>::~vector() (this=0x2a183c8 <runnables>)
     at /usr/include/c++/13/bits/stl_vector.h:732
 #19 0x0000fffee3088370 in __run_exit_handlers () from /lib64/libc.so.6
 #20 0x0000fffee3088450 [PAC] in exit () from /lib64/libc.so.6
 #21 0x0000000000c95600 [PAC] in quit_force (exit_arg=0x0, from_tty=0)
     at gdb/top.c:1822
 #22 0x0000000000609140 in quit_command (args=0x0, from_tty=0)
     at gdb/cli/cli-cmds.c:508
 #23 0x0000000000c926a4 in quit_cover () at gdb/top.c:300
 #24 0x00000000007b09d4 in async_disconnect (arg=0x0)
     at gdb/event-top.c:1230
 #25 0x0000000000548acc in invoke_async_signal_handlers ()
     at gdb/async-event.c:234
 #26 0x000000000157d2d4 in gdb_do_one_event (mstimeout=-1)
     at gdbsupport/event-loop.cc:199
 #27 0x0000000000943a84 in start_event_loop () at gdb/main.c:401
 #28 0x0000000000943bfc in captured_command_loop () at gdb/main.c:465
 #29 0x000000000094567c in captured_main (data=0xffffcb279d08)
     at gdb/main.c:1335
 #30 0x0000000000945700 in gdb_main (args=0xffffcb279d08)
     at gdb/main.c:1354
 #31 0x0000000000423ab4 in main (argc=14, argv=0xffffcb279e98)
     at gdb/gdb.c:39
...

The direct cause of the segfault is calling PyGILState_Ensure after
calling Py_Finalize.

AFAICT the problem is a race between the gdb main thread and DAP's JSON writer
thread.

On one side, we have the following events:
- DAP's JSON reader thread reads an EOF, and lets DAP's main thread known
  by writing None into read_queue
- DAP's main thread lets DAP's JSON writer thread known by writing None into
  write_queue
- DAP's JSON writer thread sees the None in its queue, and calls
  send_gdb("quit")
- a corresponding gdbpy_event is deposited in the runnables vector, to be
  run by the gdb main thread

On the other side, we have the following events:
- the gdb main thread receives a SIGHUP
- the corresponding handler calls quit_force, which calls do_final_cleanups
- one of the final cleanups is finalize_python, which calls Py_Finalize
- quit_force calls exit, which triggers the exit handlers
- one of the exit handlers is the destructor of the runnables vector
- destruction of the vector triggers destruction of the remaining element
- the remaining element is a gdbpy_event, and the destructor (indirectly)
  calls PyGILState_Ensure

It's good to note that both events (EOF and SIGHUP) are caused by this line in
the test-case:
...
catch "close -i $gdb_spawn_id"
...
where "expect close" closes the stdin and stdout file descriptors, which
causes the SIGHUP to be send.

So, for the system I'm running this on, the send_gdb("quit") is actually not
needed.

I'm not sure if we support any systems where it's actually needed.

Fix this by removing the send_gdb("quit").

Tested on aarch64-linux.

PR dap/31306
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31306
berenm pushed a commit that referenced this pull request Feb 20, 2024
@vries
[gdb/exp] Fix printing of out of bounds struct members
c3e06e6 
When building gdb with -O0 -fsanitize=address, and running test-case
gdb.ada/uninitialized_vars.exp, I run into:
...
(gdb) info locals
a = 0
z = (a => 1, b => false, c => 2.0)
=================================================================
==66372==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000097f58 at pc 0xffff52c0da1c bp 0xffffc90a1d40 sp 0xffffc90a1d80
READ of size 4 at 0x602000097f58 thread T0
    #0 0xffff52c0da18 in memmove (/lib64/libasan.so.8+0x6da18)
    #1 0xbcab24 in unsigned char* std::__copy_move_backward<false, true, std::random_access_iterator_tag>::__copy_move_b<unsigned char const, unsigned char>(unsigned char const*, unsigned char const*, unsigned char*) /usr/include/c++/13/bits/stl_algobase.h:748
    #2 0xbc9bf4 in unsigned char* std::__copy_move_backward_a2<false, unsigned char const*, unsigned char*>(unsigned char const*, unsigned char const*, unsigned char*) /usr/include/c++/13/bits/stl_algobase.h:769
    #3 0xbc898c in unsigned char* std::__copy_move_backward_a1<false, unsigned char const*, unsigned char*>(unsigned char const*, unsigned char const*, unsigned char*) /usr/include/c++/13/bits/stl_algobase.h:778
    #4 0xbc715c in unsigned char* std::__copy_move_backward_a<false, unsigned char const*, unsigned char*>(unsigned char const*, unsigned char const*, unsigned char*) /usr/include/c++/13/bits/stl_algobase.h:807
    #5 0xbc4e6c in unsigned char* std::copy_backward<unsigned char const*, unsigned char*>(unsigned char const*, unsigned char const*, unsigned char*) /usr/include/c++/13/bits/stl_algobase.h:867
    #6 0xbc2934 in void gdb::copy<unsigned char const, unsigned char>(gdb::array_view<unsigned char const>, gdb::array_view<unsigned char>) gdb/../gdbsupport/array-view.h:223
    #7 0x20e0100 in value::contents_copy_raw(value*, long, long, long) gdb/value.c:1239
    #8 0x20e9830 in value::primitive_field(long, int, type*) gdb/value.c:3078
    #9 0x20e98f8 in value_field(value*, int) gdb/value.c:3095
    #10 0xcafd64 in print_field_values gdb/ada-valprint.c:658
    #11 0xcb0fa0 in ada_val_print_struct_union gdb/ada-valprint.c:857
    #12 0xcb1bb4 in ada_value_print_inner(value*, ui_file*, int, value_print_options const*) gdb/ada-valprint.c:1042
    #13 0xc66e04 in ada_language::value_print_inner(value*, ui_file*, int, value_print_options const*) const (/home/vries/gdb/build/gdb/gdb+0xc66e04)
    #14 0x20ca1e8 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) gdb/valprint.c:1092
    #15 0x20caabc in common_val_print_checked(value*, ui_file*, int, value_print_options const*, language_defn const*) gdb/valprint.c:1184
    #16 0x196c524 in print_variable_and_value(char const*, symbol*, frame_info_ptr, ui_file*, int) gdb/printcmd.c:2355
    #17 0x1d99ca0 in print_variable_and_value_data::operator()(char const*, symbol*) gdb/stack.c:2308
    #18 0x1dabca0 in gdb::function_view<void (char const*, symbol*)>::bind<print_variable_and_value_data>(print_variable_and_value_data&)::{lambda(gdb::fv_detail::erased_callable, char const*, symbol*)#1}::operator()(gdb::fv_detail::erased_callable, char const*, symbol*) const gdb/../gdbsupport/function-view.h:305
    #19 0x1dabd14 in gdb::function_view<void (char const*, symbol*)>::bind<print_variable_and_value_data>(print_variable_and_value_data&)::{lambda(gdb::fv_detail::erased_callable, char const*, symbol*)#1}::_FUN(gdb::fv_detail::erased_callable, char const*, symbol*) gdb/../gdbsupport/function-view.h:299
    #20 0x1dab34c in gdb::function_view<void (char const*, symbol*)>::operator()(char const*, symbol*) const gdb/../gdbsupport/function-view.h:289
    #21 0x1d9963c in iterate_over_block_locals gdb/stack.c:2240
    #22 0x1d99790 in iterate_over_block_local_vars(block const*, gdb::function_view<void (char const*, symbol*)>) gdb/stack.c:2259
    #23 0x1d9a598 in print_frame_local_vars gdb/stack.c:2380
    #24 0x1d9afac in info_locals_command(char const*, int) gdb/stack.c:2458
    #25 0xfd7b30 in do_simple_func gdb/cli/cli-decode.c:95
    #26 0xfe5a2c in cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735
    #27 0x1f03790 in execute_command(char const*, int) gdb/top.c:575
    #28 0x1384080 in command_handler(char const*) gdb/event-top.c:566
    #29 0x1384e2c in command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:802
    #30 0x1f731e4 in tui_command_line_handler gdb/tui/tui-interp.c:104
    #31 0x1382a58 in gdb_rl_callback_handler gdb/event-top.c:259
    #32 0x21dbb80 in rl_callback_read_char readline/readline/callback.c:290
    #33 0x1382510 in gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195
    #34 0x138277c in gdb_rl_callback_read_char_wrapper gdb/event-top.c:234
    #35 0x1fe9b40 in stdin_event_handler gdb/ui.c:155
    #36 0x35ff1bc in handle_file_event gdbsupport/event-loop.cc:573
    #37 0x35ff9d8 in gdb_wait_for_event gdbsupport/event-loop.cc:694
    #38 0x35fd284 in gdb_do_one_event(int) gdbsupport/event-loop.cc:264
    #39 0x1768080 in start_event_loop gdb/main.c:408
    #40 0x17684c4 in captured_command_loop gdb/main.c:472
    #41 0x176cfc8 in captured_main gdb/main.c:1342
    #42 0x176d088 in gdb_main(captured_main_args*) gdb/main.c:1361
    #43 0xb73edc in main gdb/gdb.c:39
    #44 0xffff519b09d8 in __libc_start_call_main (/lib64/libc.so.6+0x309d8)
    #45 0xffff519b0aac in __libc_start_main@@GLIBC_2.34 (/lib64/libc.so.6+0x30aac)
    #46 0xb73c2c in _start (/home/vries/gdb/build/gdb/gdb+0xb73c2c)

0x602000097f58 is located 0 bytes after 8-byte region [0x602000097f50,0x602000097f58)
allocated by thread T0 here:
    #0 0xffff52c65218 in calloc (/lib64/libasan.so.8+0xc5218)
    #1 0xcbc278 in xcalloc gdb/alloc.c:97
    #2 0x35f21e8 in xzalloc(unsigned long) gdbsupport/common-utils.cc:29
    #3 0x20de270 in value::allocate_contents(bool) gdb/value.c:937
    #4 0x20edc08 in value::fetch_lazy() gdb/value.c:4033
    #5 0x20dadc0 in value::entirely_covered_by_range_vector(std::vector<range, std::allocator<range> > const&) gdb/value.c:229
    #6 0xcb2298 in value::entirely_optimized_out() gdb/value.h:560
    #7 0x20ca6fc in value_check_printable gdb/valprint.c:1133
    #8 0x20caa8c in common_val_print_checked(value*, ui_file*, int, value_print_options const*, language_defn const*) gdb/valprint.c:1182
    #9 0x196c524 in print_variable_and_value(char const*, symbol*, frame_info_ptr, ui_file*, int) gdb/printcmd.c:2355
    #10 0x1d99ca0 in print_variable_and_value_data::operator()(char const*, symbol*) gdb/stack.c:2308
    #11 0x1dabca0 in gdb::function_view<void (char const*, symbol*)>::bind<print_variable_and_value_data>(print_variable_and_value_data&)::{lambda(gdb::fv_detail::erased_callable, char const*, symbol*)#1}::operator()(gdb::fv_detail::erased_callable, char const*, symbol*) const gdb/../gdbsupport/function-view.h:305
    #12 0x1dabd14 in gdb::function_view<void (char const*, symbol*)>::bind<print_variable_and_value_data>(print_variable_and_value_data&)::{lambda(gdb::fv_detail::erased_callable, char const*, symbol*)#1}::_FUN(gdb::fv_detail::erased_callable, char const*, symbol*) gdb/../gdbsupport/function-view.h:299
    #13 0x1dab34c in gdb::function_view<void (char const*, symbol*)>::operator()(char const*, symbol*) const gdb/../gdbsupport/function-view.h:289
    #14 0x1d9963c in iterate_over_block_locals gdb/stack.c:2240
    #15 0x1d99790 in iterate_over_block_local_vars(block const*, gdb::function_view<void (char const*, symbol*)>) gdb/stack.c:2259
    #16 0x1d9a598 in print_frame_local_vars gdb/stack.c:2380
    #17 0x1d9afac in info_locals_command(char const*, int) gdb/stack.c:2458
    #18 0xfd7b30 in do_simple_func gdb/cli/cli-decode.c:95
    #19 0xfe5a2c in cmd_func(cmd_list_element*, char const*, int) gdb/cli/cli-decode.c:2735
    #20 0x1f03790 in execute_command(char const*, int) gdb/top.c:575
    #21 0x1384080 in command_handler(char const*) gdb/event-top.c:566
    #22 0x1384e2c in command_line_handler(std::unique_ptr<char, gdb::xfree_deleter<char> >&&) gdb/event-top.c:802
    #23 0x1f731e4 in tui_command_line_handler gdb/tui/tui-interp.c:104
    #24 0x1382a58 in gdb_rl_callback_handler gdb/event-top.c:259
    #25 0x21dbb80 in rl_callback_read_char readline/readline/callback.c:290
    #26 0x1382510 in gdb_rl_callback_read_char_wrapper_noexcept gdb/event-top.c:195
    #27 0x138277c in gdb_rl_callback_read_char_wrapper gdb/event-top.c:234
    #28 0x1fe9b40 in stdin_event_handler gdb/ui.c:155
    #29 0x35ff1bc in handle_file_event gdbsupport/event-loop.cc:573

SUMMARY: AddressSanitizer: heap-buffer-overflow (/lib64/libasan.so.8+0x6da18) in memmove
...

The error happens when trying to print either variable y or y2:
...
   type Variable_Record (A : Boolean := True) is record
      case A is
         when True =>
            B : Integer;
         when False =>
            C : Float;
            D : Integer;
      end case;
   end record;
   Y  : Variable_Record := (A => True, B => 1);
   Y2 : Variable_Record := (A => False, C => 1.0, D => 2);
...
when the variables are uninitialized.

The error happens only when printing the entire variable:
...
(gdb) p y.a
$2 = 216
(gdb) p y.b
There is no member named b.
(gdb) p y.c
$3 = 9.18340949e-41
(gdb) p y.d
$4 = 1
(gdb) p y
<AddressSanitizer: heap-buffer-overflow>
...

The error happens as follows:
- field a functions as discriminant, choosing either the b, or c+d variant.
- when y.a happens to be set to 216, as above, gdb interprets this as the
  variable having the c+d variant (which is why trying to print y.b fails).
- when printing y, gdb allocates a value, copies the bytes into it from the
  target, and then prints the value.
- gdb allocates the value using the type size, which is 8.  It's 8 because
  that's what the DW_AT_byte_size indicates.  Note that for valid values of a,
  it gives correct results: if a is 0 (c+d variant), size is 12, if a is 1
  (b variant), size is 8.
- gdb tries to print field d, which is at an 8 byte offset, and that results
  in a out-of-bounds access for the allocated 8-byte value.

Fix this by handling this case in value::contents_copy_raw, such that we have:
...
(gdb) p y
$1 = (a => 24, c => 9.18340949e-41,
      d => <error reading variable: access outside bounds of object>)
...

An alternative (additional) fix could be this: in compute_variant_fields_inner
gdb reads the discriminant y.a to decide which variant is active.  It would be
nice to detect that the value (y.a == 24) is not a valid Boolean, and give up
on choosing a variant altoghether.  However, the situation regarding the
internal type CODE_TYPE_BOOL is currently ambiguous (see PR31282) and it's not
possible to reliably decide what valid values are.

The test-case source file gdb.ada/uninitialized-variable-record/parse.adb is
a reduced version of gdb.ada/uninitialized_vars/parse.adb, so it copies the
copyright years.

Note that the test-case needs gcc-12 or newer, it's unsupported for older gcc
versions. [ So, it would be nice to rewrite it into a dwarf assembly
test-case. ]

The test-case loops over all languages.  This is inherited from an earlier
attempt to fix this, which had language-specific fixes (in print_field_values,
cp_print_value_fields, pascal_object_print_value_fields and
f_language::value_print_inner).  I've left this in, but I suppose it's not
strictly necessary anymore.

Tested on x86_64-linux.

PR exp/31258
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31258
berenm pushed a commit that referenced this pull request Feb 20, 2024
@barisaktemur @moguzhankarakaya
gdb, python: selectively omit enabling stdin in gdb.execute
046a94c 
From the Python API, we can execute GDB commands via gdb.execute.  If
the command gives an exception, however, we need to recover the GDB
prompt and enable stdin, because the exception does not reach
top-level GDB or normal_stop.  This was done in commit

  commit 1ba1ac8
  Author: Andrew Burgess <andrew.burgess@embecosm.com>
  Date:   Tue Nov 19 11:17:20 2019 +0000

    gdb: Enable stdin on exception in execute_gdb_command

with the following code:

  catch (const gdb_exception &except)
    {
      /* If an exception occurred then we won't hit normal_stop (), or have
         an exception reach the top level of the event loop, which are the
         two usual places in which stdin would be re-enabled. So, before we
         convert the exception and continue back in Python, we should
         re-enable stdin here.  */
      async_enable_stdin ();
      GDB_PY_HANDLE_EXCEPTION (except);
    }

In this patch, we explain what happens when we run a GDB command in
the context of a synchronous command, e.g.  via Python observer
notifications.

As an example, suppose we have the following objfile event listener,
specified in a file named file.py:

~~~
import gdb

class MyListener:
    def __init__(self):
        gdb.events.new_objfile.connect(self.handle_new_objfile_event)
        self.processed_objfile = False

    def handle_new_objfile_event(self, event):
        if self.processed_objfile:
            return

        print("loading " + event.new_objfile.filename)
        self.processed_objfile = True
        gdb.execute('add-inferior -no-connection')
        gdb.execute('inferior 2')
        gdb.execute('target remote | gdbserver - /tmp/a.out')
        gdb.execute('inferior 1')

the_listener = MyListener()
~~~

Using this Python file, we see the behavior below:

  $ gdb -q -ex "source file.py" -ex "run" --args a.out
  Reading symbols from a.out...
  Starting program: /tmp/a.out
  loading /lib64/ld-linux-x86-64.so.2
  [New inferior 2]
  Added inferior 2
  [Switching to inferior 2 [<null>] (<noexec>)]
  stdin/stdout redirected
  Process /tmp/a.out created; pid = 3075406
  Remote debugging using stdio
  Reading /tmp/a.out from remote target...
  ...
  [Switching to inferior 1 [process 3075400] (/tmp/a.out)]
  [Switching to thread 1.1 (process 3075400)]
  #0  0x00007ffff7fe3290 in ?? () from /lib64/ld-linux-x86-64.so.2
  (gdb) [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  [Inferior 1 (process 3075400) exited normally]

Note how the GDB prompt comes in-between the debugger output.  We have this
obscure behavior, because the executed command, "target remote", triggers
an invocation of `normal_stop` that enables stdin.  After that, however,
the Python notification context completes and GDB continues with its normal
flow of executing the 'run' command.  This can be seen in the call stack
below:

  (top-gdb) bt
  #0  async_enable_stdin () at src/gdb/event-top.c:523
  #1  0x00005555561c3acd in normal_stop () at src/gdb/infrun.c:9432
  #2  0x00005555561b328e in start_remote (from_tty=0) at src/gdb/infrun.c:3801
  #3  0x0000555556441224 in remote_target::start_remote_1 (this=0x5555587882e0, from_tty=0, extended_p=0) at src/gdb/remote.c:5225
  #4  0x000055555644166c in remote_target::start_remote (this=0x5555587882e0, from_tty=0, extended_p=0) at src/gdb/remote.c:5316
  #5  0x00005555564430cf in remote_target::open_1 (name=0x55555878525e "| gdbserver - /tmp/a.out", from_tty=0, extended_p=0) at src/gdb/remote.c:6175
  #6  0x0000555556441707 in remote_target::open (name=0x55555878525e "| gdbserver - /tmp/a.out", from_tty=0) at src/gdb/remote.c:5338
  #7  0x00005555565ea63f in open_target (args=0x55555878525e "| gdbserver - /tmp/a.out", from_tty=0, command=0x555558589280)  at src/gdb/target.c:824
  #8  0x0000555555f0d89a in cmd_func (cmd=0x555558589280, args=0x55555878525e "| gdbserver - /tmp/a.out", from_tty=0) at src/gdb/cli/cli-decode.c:2735
  #9  0x000055555661fb42 in execute_command (p=0x55555878529e "t", from_tty=0) at src/gdb/top.c:575
  #10 0x0000555555f1a506 in execute_control_command_1 (cmd=0x555558756f00, from_tty=0) at src/gdb/cli/cli-script.c:529
  #11 0x0000555555f1abea in execute_control_command (cmd=0x555558756f00, from_tty=0) at src/gdb/cli/cli-script.c:701
  #12 0x0000555555f19fc7 in execute_control_commands (cmdlines=0x555558756f00, from_tty=0) at src/gdb/cli/cli-script.c:411
  #13 0x0000555556400d91 in execute_gdb_command (self=0x7ffff43b5d00, args=0x7ffff440ab60, kw=0x0) at src/gdb/python/python.c:700
  #14 0x00007ffff7a96023 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #15 0x00007ffff7a4dadc in _PyObject_MakeTpCall () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #16 0x00007ffff79e9a1c in _PyEval_EvalFrameDefault () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #17 0x00007ffff7b303af in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #18 0x00007ffff7a50358 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #19 0x00007ffff7a4f3f4 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #20 0x00007ffff7a4f883 in PyObject_CallFunctionObjArgs () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #21 0x00005555563a9758 in evpy_emit_event (event=0x7ffff42b5430, registry=0x7ffff42b4690) at src/gdb/python/py-event.c:104
  #22 0x00005555563cb874 in emit_new_objfile_event (objfile=0x555558761700) at src/gdb/python/py-newobjfileevent.c:52
  #23 0x00005555563b53bc in python_new_objfile (objfile=0x555558761700) at src/gdb/python/py-inferior.c:195
  #24 0x0000555555d6dff0 in std::__invoke_impl<void, void (*&)(objfile*), objfile*> (__f=@0x5555585b5860: 0x5555563b5360 <python_new_objfile(objfile*)>) at /usr/include/c++/11/bits/invoke.h:61
  #25 0x0000555555d6be18 in std::__invoke_r<void, void (*&)(objfile*), objfile*> (__fn=@0x5555585b5860: 0x5555563b5360 <python_new_objfile(objfile*)>) at /usr/include/c++/11/bits/invoke.h:111
  #26 0x0000555555d69661 in std::_Function_handler<void (objfile*), void (*)(objfile*)>::_M_invoke(std::_Any_data const&, objfile*&&) (__functor=..., __args#0=@0x7fffffffd080: 0x555558761700) at /usr/include/c++/11/bits/std_function.h:290
  #27 0x0000555556314caf in std::function<void (objfile*)>::operator()(objfile*) const (this=0x5555585b5860, __args#0=0x555558761700) at /usr/include/c++/11/bits/std_function.h:590
  #28 0x000055555631444e in gdb::observers::observable<objfile*>::notify (this=0x55555836eea0 <gdb::observers::new_objfile>, args#0=0x555558761700) at src/gdb/../gdbsupport/observable.h:166
  #29 0x0000555556599b3f in symbol_file_add_with_addrs (abfd=..., name=0x55555875d310 "/lib64/ld-linux-x86-64.so.2", add_flags=..., addrs=0x7fffffffd2f0, flags=..., parent=0x0) at src/gdb/symfile.c:1125
  #30 0x0000555556599ca4 in symbol_file_add_from_bfd (abfd=..., name=0x55555875d310 "/lib64/ld-linux-x86-64.so.2", add_flags=..., addrs=0x7fffffffd2f0, flags=..., parent=0x0) at src/gdb/symfile.c:1160
  #31 0x0000555556546371 in solib_read_symbols (so=..., flags=...) at src/gdb/solib.c:692
  #32 0x0000555556546f0f in solib_add (pattern=0x0, from_tty=0, readsyms=1) at src/gdb/solib.c:1015
  #33 0x0000555556539891 in enable_break (info=0x55555874e180, from_tty=0) at src/gdb/solib-svr4.c:2416
  #34 0x000055555653b305 in svr4_solib_create_inferior_hook (from_tty=0) at src/gdb/solib-svr4.c:3058
  #35 0x0000555556547cee in solib_create_inferior_hook (from_tty=0) at src/gdb/solib.c:1217
  #36 0x0000555556196f6a in post_create_inferior (from_tty=0) at src/gdb/infcmd.c:275
  #37 0x0000555556197670 in run_command_1 (args=0x0, from_tty=1, run_how=RUN_NORMAL) at src/gdb/infcmd.c:486
  #38 0x000055555619783f in run_command (args=0x0, from_tty=1) at src/gdb/infcmd.c:512
  #39 0x0000555555f0798d in do_simple_func (args=0x0, from_tty=1, c=0x555558567510) at src/gdb/cli/cli-decode.c:95
  #40 0x0000555555f0d89a in cmd_func (cmd=0x555558567510, args=0x0, from_tty=1) at src/gdb/cli/cli-decode.c:2735
  #41 0x000055555661fb42 in execute_command (p=0x7fffffffe2c4 "", from_tty=1) at src/gdb/top.c:575
  #42 0x000055555626303b in catch_command_errors (command=0x55555661f4ab <execute_command(char const*, int)>, arg=0x7fffffffe2c1 "run", from_tty=1, do_bp_actions=true) at src/gdb/main.c:513
  #43 0x000055555626328a in execute_cmdargs (cmdarg_vec=0x7fffffffdaf0, file_type=CMDARG_FILE, cmd_type=CMDARG_COMMAND, ret=0x7fffffffda3c) at src/gdb/main.c:612
  #44 0x0000555556264849 in captured_main_1 (context=0x7fffffffdd40) at src/gdb/main.c:1293
  #45 0x0000555556264a7f in captured_main (data=0x7fffffffdd40) at src/gdb/main.c:1314
  #46 0x0000555556264b2e in gdb_main (args=0x7fffffffdd40) at src/gdb/main.c:1343
  #47 0x0000555555ceccab in main (argc=9, argv=0x7fffffffde78) at src/gdb/gdb.c:39
  (top-gdb)

The use of the "target remote" command here is just an example.  In
principle, we would reproduce the problem with any command that
triggers an invocation of `normal_stop`.

To omit enabling the stdin in `normal_stop`, we would have to check the
context we are in.  Since we cannot do that, we add a new field to
`struct ui` to track whether the prompt was already blocked, and set
the tracker flag in the Python context before executing a GDB command.

After applying this patch, the output becomes

  ...
  Reading symbols from a.out...
  Starting program: /tmp/a.out
  loading /lib64/ld-linux-x86-64.so.2
  [New inferior 2]
  Added inferior 2
  [Switching to inferior 2 [<null>] (<noexec>)]
  stdin/stdout redirected
  Process /tmp/a.out created; pid = 3032261
  Remote debugging using stdio
  Reading /tmp/a.out from remote target...
  ...
  [Switching to inferior 1 [process 3032255] (/tmp/a.out)]
  [Switching to thread 1.1 (process 3032255)]
  #0  0x00007ffff7fe3290 in ?? () from /lib64/ld-linux-x86-64.so.2
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
  [Inferior 1 (process 3032255) exited normally]
  (gdb)

Let's now consider a secondary scenario, where the command executed from
the Python raises an error.  As an example, suppose we have the Python
file below:

    def handle_new_objfile_event(self, event):
        ...
        print("loading " + event.new_objfile.filename)
        self.processed_objfile = True
        gdb.execute('print a')

The executed command, "print a", gives an error because "a" is not
defined.  Without this patch, we see the behavior below, where the
prompt is again placed incorrectly:

  ...
  Reading symbols from /tmp/a.out...
  Starting program: /tmp/a.out
  loading /lib64/ld-linux-x86-64.so.2
  Python Exception <class 'gdb.error'>: No symbol "a" in current context.
  (gdb) [Inferior 1 (process 3980401) exited normally]

This time, `async_enable_stdin` is called from the 'catch' block in
`execute_gdb_command`:

  (top-gdb) bt
  #0  async_enable_stdin () at src/gdb/event-top.c:523
  #1  0x0000555556400f0a in execute_gdb_command (self=0x7ffff43b5d00, args=0x7ffff440ab60, kw=0x0) at src/gdb/python/python.c:713
  #2  0x00007ffff7a96023 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #3  0x00007ffff7a4dadc in _PyObject_MakeTpCall () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #4  0x00007ffff79e9a1c in _PyEval_EvalFrameDefault () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #5  0x00007ffff7b303af in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #6  0x00007ffff7a50358 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #7  0x00007ffff7a4f3f4 in ?? () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #8  0x00007ffff7a4f883 in PyObject_CallFunctionObjArgs () from /lib/x86_64-linux-gnu/libpython3.10.so.1.0
  #9  0x00005555563a9758 in evpy_emit_event (event=0x7ffff42b5430, registry=0x7ffff42b4690) at src/gdb/python/py-event.c:104
  #10 0x00005555563cb874 in emit_new_objfile_event (objfile=0x555558761410) at src/gdb/python/py-newobjfileevent.c:52
  #11 0x00005555563b53bc in python_new_objfile (objfile=0x555558761410) at src/gdb/python/py-inferior.c:195
  #12 0x0000555555d6dff0 in std::__invoke_impl<void, void (*&)(objfile*), objfile*> (__f=@0x5555585b5860: 0x5555563b5360 <python_new_objfile(objfile*)>) at /usr/include/c++/11/bits/invoke.h:61
  #13 0x0000555555d6be18 in std::__invoke_r<void, void (*&)(objfile*), objfile*> (__fn=@0x5555585b5860: 0x5555563b5360 <python_new_objfile(objfile*)>) at /usr/include/c++/11/bits/invoke.h:111
  #14 0x0000555555d69661 in std::_Function_handler<void (objfile*), void (*)(objfile*)>::_M_invoke(std::_Any_data const&, objfile*&&) (__functor=..., __args#0=@0x7fffffffd080: 0x555558761410) at /usr/include/c++/11/bits/std_function.h:290
  #15 0x0000555556314caf in std::function<void (objfile*)>::operator()(objfile*) const (this=0x5555585b5860, __args#0=0x555558761410) at /usr/include/c++/11/bits/std_function.h:590
  #16 0x000055555631444e in gdb::observers::observable<objfile*>::notify (this=0x55555836eea0 <gdb::observers::new_objfile>, args#0=0x555558761410) at src/gdb/../gdbsupport/observable.h:166
  #17 0x0000555556599b3f in symbol_file_add_with_addrs (abfd=..., name=0x55555875d020 "/lib64/ld-linux-x86-64.so.2", add_flags=..., addrs=0x7fffffffd2f0, flags=..., parent=0x0) at src/gdb/symfile.c:1125
  #18 0x0000555556599ca4 in symbol_file_add_from_bfd (abfd=..., name=0x55555875d020 "/lib64/ld-linux-x86-64.so.2", add_flags=..., addrs=0x7fffffffd2f0, flags=..., parent=0x0) at src/gdb/symfile.c:1160
  #19 0x0000555556546371 in solib_read_symbols (so=..., flags=...) at src/gdb/solib.c:692
  #20 0x0000555556546f0f in solib_add (pattern=0x0, from_tty=0, readsyms=1) at src/gdb/solib.c:1015
  #21 0x0000555556539891 in enable_break (info=0x55555874a670, from_tty=0) at src/gdb/solib-svr4.c:2416
  #22 0x000055555653b305 in svr4_solib_create_inferior_hook (from_tty=0) at src/gdb/solib-svr4.c:3058
  #23 0x0000555556547cee in solib_create_inferior_hook (from_tty=0) at src/gdb/solib.c:1217
  #24 0x0000555556196f6a in post_create_inferior (from_tty=0) at src/gdb/infcmd.c:275
  #25 0x0000555556197670 in run_command_1 (args=0x0, from_tty=1, run_how=RUN_NORMAL) at src/gdb/infcmd.c:486
  #26 0x000055555619783f in run_command (args=0x0, from_tty=1) at src/gdb/infcmd.c:512
  #27 0x0000555555f0798d in do_simple_func (args=0x0, from_tty=1, c=0x555558567510) at src/gdb/cli/cli-decode.c:95
  #28 0x0000555555f0d89a in cmd_func (cmd=0x555558567510, args=0x0, from_tty=1) at src/gdb/cli/cli-decode.c:2735
  #29 0x000055555661fb42 in execute_command (p=0x7fffffffe2c4 "", from_tty=1) at src/gdb/top.c:575
  #30 0x000055555626303b in catch_command_errors (command=0x55555661f4ab <execute_command(char const*, int)>, arg=0x7fffffffe2c1 "run", from_tty=1, do_bp_actions=true) at src/gdb/main.c:513
  #31 0x000055555626328a in execute_cmdargs (cmdarg_vec=0x7fffffffdaf0, file_type=CMDARG_FILE, cmd_type=CMDARG_COMMAND, ret=0x7fffffffda3c) at src/gdb/main.c:612
  #32 0x0000555556264849 in captured_main_1 (context=0x7fffffffdd40) at src/gdb/main.c:1293
  #33 0x0000555556264a7f in captured_main (data=0x7fffffffdd40) at src/gdb/main.c:1314
  #34 0x0000555556264b2e in gdb_main (args=0x7fffffffdd40) at src/gdb/main.c:1343
  #35 0x0000555555ceccab in main (argc=9, argv=0x7fffffffde78) at src/gdb/gdb.c:39
  (top-gdb)

Again, after we enable stdin, GDB continues with its normal flow
of the 'run' command and receives the inferior's exit event, where
it would have enabled stdin, if we had not done it prematurely.

  (top-gdb) bt
  #0  async_enable_stdin () at src/gdb/event-top.c:523
  #1  0x00005555561c3acd in normal_stop () at src/gdb/infrun.c:9432
  #2  0x00005555561b5bf1 in fetch_inferior_event () at src/gdb/infrun.c:4700
  #3  0x000055555618d6a7 in inferior_event_handler (event_type=INF_REG_EVENT) at src/gdb/inf-loop.c:42
  #4  0x000055555620ecdb in handle_target_event (error=0, client_data=0x0) at src/gdb/linux-nat.c:4316
  #5  0x0000555556f33035 in handle_file_event (file_ptr=0x5555587024e0, ready_mask=1) at src/gdbsupport/event-loop.cc:573
  #6  0x0000555556f3362f in gdb_wait_for_event (block=0) at src/gdbsupport/event-loop.cc:694
  #7  0x0000555556f322cd in gdb_do_one_event (mstimeout=-1) at src/gdbsupport/event-loop.cc:217
  #8  0x0000555556262df8 in start_event_loop () at src/gdb/main.c:407
  #9  0x0000555556262f85 in captured_command_loop () at src/gdb/main.c:471
  #10 0x0000555556264a84 in captured_main (data=0x7fffffffdd40) at src/gdb/main.c:1324
  #11 0x0000555556264b2e in gdb_main (args=0x7fffffffdd40) at src/gdb/main.c:1343
  #12 0x0000555555ceccab in main (argc=9, argv=0x7fffffffde78) at src/gdb/gdb.c:39
  (top-gdb)

The solution implemented by this patch addresses the problem.  After
applying the patch, the output becomes

  $ gdb -q -ex "source file.py" -ex "run" --args a.out
  Reading symbols from /tmp/a.out...
  Starting program: /tmp/a.out
  loading /lib64/ld-linux-x86-64.so.2
  Python Exception <class 'gdb.error'>: No symbol "a" in current context.
  [Inferior 1 (process 3984511) exited normally]
  (gdb)

Regression-tested on X86_64 Linux using the default board file (i.e.  unix).

Co-Authored-By: Oguzhan Karakaya <oguzhan.karakaya@intel.com>
Reviewed-By: Guinevere Larsen <blarsen@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>
berenm pushed a commit that referenced this pull request Apr 28, 2024
@vries
[gdb/remote] Fix abort on REMOTE_CLOSE_ERROR
e705ee1 
When running test-case gdb.server/connect-with-no-symbol-file.exp on
aarch64-linux (specifically, an opensuse leap 15.5 container on a
fedora asahi 39 system), I run into:
...
(gdb) detach^M
Detaching from program: target:connect-with-no-symbol-file, process 185104^M
Ending remote debugging.^M
terminate called after throwing an instance of 'gdb_exception_error'^M
...

The detailed backtrace of the corefile is:
...
 (gdb) bt
 #0  0x0000ffff75504f54 in raise () from /lib64/libpthread.so.0
 #1  0x00000000007a86b4 in handle_fatal_signal (sig=6)
     at gdb/event-top.c:926
 #2  <signal handler called>
 #3  0x0000ffff74b977b4 in raise () from /lib64/libc.so.6
 #4  0x0000ffff74b98c18 in abort () from /lib64/libc.so.6
 #5  0x0000ffff74ea26f4 in __gnu_cxx::__verbose_terminate_handler() ()
    from /usr/lib64/libstdc++.so.6
 #6  0x0000ffff74ea011c in ?? () from /usr/lib64/libstdc++.so.6
 #7  0x0000ffff74ea0180 in std::terminate() () from /usr/lib64/libstdc++.so.6
 #8  0x0000ffff74ea0464 in __cxa_throw () from /usr/lib64/libstdc++.so.6
 #9  0x0000000001548870 in throw_it (reason=RETURN_ERROR,
     error=TARGET_CLOSE_ERROR, fmt=0x16c7810 "Remote connection closed", ap=...)
     at gdbsupport/common-exceptions.cc:203
 #10 0x0000000001548920 in throw_verror (error=TARGET_CLOSE_ERROR,
     fmt=0x16c7810 "Remote connection closed", ap=...)
     at gdbsupport/common-exceptions.cc:211
 #11 0x0000000001548a00 in throw_error (error=TARGET_CLOSE_ERROR,
     fmt=0x16c7810 "Remote connection closed")
     at gdbsupport/common-exceptions.cc:226
 #12 0x0000000000ac8f2c in remote_target::readchar (this=0x233d3d90, timeout=2)
     at gdb/remote.c:9856
 #13 0x0000000000ac9f04 in remote_target::getpkt (this=0x233d3d90,
     buf=0x233d40a8, forever=false, is_notif=0x0) at gdb/remote.c:10326
 #14 0x0000000000acf3d0 in remote_target::remote_hostio_send_command
     (this=0x233d3d90, command_bytes=13, which_packet=17,
     remote_errno=0xfffff1a3cf38, attachment=0xfffff1a3ce88,
     attachment_len=0xfffff1a3ce90) at gdb/remote.c:12567
 #15 0x0000000000ad03bc in remote_target::fileio_fstat (this=0x233d3d90, fd=3,
     st=0xfffff1a3d020, remote_errno=0xfffff1a3cf38)
     at gdb/remote.c:12979
 #16 0x0000000000c39878 in target_fileio_fstat (fd=0, sb=0xfffff1a3d020,
     target_errno=0xfffff1a3cf38) at gdb/target.c:3315
 #17 0x00000000007eee5c in target_fileio_stream::stat (this=0x233d4400,
     abfd=0x2323fc40, sb=0xfffff1a3d020) at gdb/gdb_bfd.c:467
 #18 0x00000000007f012c in <lambda(bfd*, void*, stat*)>::operator()(bfd *,
     void *, stat *) const (__closure=0x0, abfd=0x2323fc40, stream=0x233d4400,
     sb=0xfffff1a3d020) at gdb/gdb_bfd.c:955
 #19 0x00000000007f015c in <lambda(bfd*, void*, stat*)>::_FUN(bfd *, void *,
     stat *) () at gdb/gdb_bfd.c:956
 #20 0x0000000000f9b838 in opncls_bstat (abfd=0x2323fc40, sb=0xfffff1a3d020)
     at bfd/opncls.c:665
 #21 0x0000000000f90adc in bfd_stat (abfd=0x2323fc40, statbuf=0xfffff1a3d020)
     at bfd/bfdio.c:431
 #22 0x000000000065fe20 in reopen_exec_file () at gdb/corefile.c:52
 #23 0x0000000000c3a3e8 in generic_mourn_inferior ()
     at gdb/target.c:3642
 #24 0x0000000000abf3f0 in remote_unpush_target (target=0x233d3d90)
     at gdb/remote.c:6067
 #25 0x0000000000aca8b0 in remote_target::mourn_inferior (this=0x233d3d90)
     at gdb/remote.c:10587
 #26 0x0000000000c387cc in target_mourn_inferior (
     ptid=<error reading variable: Cannot access memory at address 0x2d310>)
     at gdb/target.c:2738
 #27 0x0000000000abfff0 in remote_target::remote_detach_1 (this=0x233d3d90,
     inf=0x22fce540, from_tty=1) at gdb/remote.c:6421
 #28 0x0000000000ac0094 in remote_target::detach (this=0x233d3d90,
     inf=0x22fce540, from_tty=1) at gdb/remote.c:6436
 #29 0x0000000000c37c3c in target_detach (inf=0x22fce540, from_tty=1)
     at gdb/target.c:2526
 #30 0x0000000000860424 in detach_command (args=0x0, from_tty=1)
    at gdb/infcmd.c:2817
 #31 0x000000000060b594 in do_simple_func (args=0x0, from_tty=1, c=0x231431a0)
     at gdb/cli/cli-decode.c:94
 #32 0x00000000006108c8 in cmd_func (cmd=0x231431a0, args=0x0, from_tty=1)
     at gdb/cli/cli-decode.c:2741
 #33 0x0000000000c65a94 in execute_command (p=0x232e52f6 "", from_tty=1)
     at gdb/top.c:570
 #34 0x00000000007a7d2c in command_handler (command=0x232e52f0 "")
     at gdb/event-top.c:566
 #35 0x00000000007a8290 in command_line_handler (rl=...)
     at gdb/event-top.c:802
 #36 0x0000000000c9092c in tui_command_line_handler (rl=...)
     at gdb/tui/tui-interp.c:103
 #37 0x00000000007a750c in gdb_rl_callback_handler (rl=0x23385330 "detach")
     at gdb/event-top.c:258
 #38 0x0000000000d910f4 in rl_callback_read_char ()
     at readline/readline/callback.c:290
 #39 0x00000000007a7338 in gdb_rl_callback_read_char_wrapper_noexcept ()
     at gdb/event-top.c:194
 #40 0x00000000007a73f0 in gdb_rl_callback_read_char_wrapper
     (client_data=0x22fbf640) at gdb/event-top.c:233
 #41 0x0000000000cbee1c in stdin_event_handler (error=0, client_data=0x22fbf640)
     at gdb/ui.c:154
 #42 0x000000000154ed60 in handle_file_event (file_ptr=0x232be730, ready_mask=1)
     at gdbsupport/event-loop.cc:572
 #43 0x000000000154f21c in gdb_wait_for_event (block=1)
     at gdbsupport/event-loop.cc:693
 #44 0x000000000154dec4 in gdb_do_one_event (mstimeout=-1)
    at gdbsupport/event-loop.cc:263
 #45 0x0000000000910f98 in start_event_loop () at gdb/main.c:400
 #46 0x0000000000911130 in captured_command_loop () at gdb/main.c:464
 #47 0x0000000000912b5c in captured_main (data=0xfffff1a3db58)
     at gdb/main.c:1338
 #48 0x0000000000912bf4 in gdb_main (args=0xfffff1a3db58)
     at gdb/main.c:1357
 #49 0x00000000004170f4 in main (argc=10, argv=0xfffff1a3dcc8)
     at gdb/gdb.c:38
 (gdb)
...

The abort happens because a c++ exception escapes to c code, specifically
opncls_bstat in bfd/opncls.c.  Compiling with -fexceptions works around this.

Fix this by catching the exception just before it escapes, in stat_trampoline
and likewise in few similar spot.

Add a new template catch_exceptions to do so in a consistent way.

Tested on aarch64-linux.

Approved-by: Pedro Alves <pedro@palves.net>

PR remote/31577
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31577
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers
No reviews
Assignees
No one assigned
Labels
None yet
Projects
None yet
Milestone
No milestone
1 participant
@kiraskyler