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symbols with same (empty) name but different type #202

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jstancek opened this issue May 23, 2014 · 2 comments · Fixed by #215
Closed

symbols with same (empty) name but different type #202

jstancek opened this issue May 23, 2014 · 2 comments · Fixed by #215

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@jstancek
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I came across a kpatch-build error, while trying following patch:

# cat tp_trivial_change_to_function_with_tp.patch
diff --git a/kernel/signal.c b/kernel/signal.c
index 50e4107..2a69b78 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2196,6 +2196,9 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
    struct signal_struct *signal = current->signal;
    int signr;

+   if (!current)
+       return 0;
+
    if (unlikely(current->task_works))
        task_work_run();

$ kpatch-build tp_trivial_change_to_function_with_tp.patch -s /root/rpmbuild/BUILD/kernel-3.10.0-123.el7/linux-3.10.0-123.el7.x86_64 --debug
DEBUG mode enabled
Copying source to /root/.kpatch/src
Testing patch file
checking file kernel/signal.c
Building original kernel
Building patched kernel
Detecting changed objects
Rebuilding changed objects
Extracting new and modified ELF sections
signal.o: symbol info mismatch: 
/usr/local/libexec/kpatch/create-diff-object: unreconcilable difference
ERROR: kpatch build failed. Check /tmp/kpatch-build-1400832771.log for more details.

$ tail /tmp/kpatch-build-1400832771.log
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CALL    /root/.kpatch/src/scripts/checksyscalls.sh
  CC      scripts/mod/devicetable-offsets.s
  GEN     scripts/mod/devicetable-offsets.h
  HOSTCC  scripts/mod/file2alias.o
  HOSTLD  scripts/mod/modpost
  CC      kernel/signal.o
signal.o: symbol info mismatch: 
/usr/local/libexec/kpatch/create-diff-object: unreconcilable difference

Looking at debug output of patched object, I could see 2 symbols with same (empty) name ""
but different type:

=== symbol list (751 entries) ===
sym 00, type 0, bind 0, ndx 00, name 
...
sym 425, type 4, bind 0, ndx 65521, name

I tried following change, which allowed me to progress further:

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 655b05d..9e2a57a 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -601,7 +601,7 @@ void kpatch_correlate_symbols(struct list_head *symlist1, struct list_head *syml

        list_for_each_entry(sym1, symlist1, list) {
                list_for_each_entry(sym2, symlist2, list) {
-                       if (!strcmp(sym1->name, sym2->name)) {
+                       if (!strcmp(sym1->name, sym2->name) && (sym1->type == sym2->type)) {
                                sym1->twin = sym2;
                                sym2->twin = sym1;
                                /* set initial status, might change */

Debug output:

sym 00, type 0, bind 0, ndx 00, name  (SAME)
...
sym 425, type 4, bind 0, ndx 65521, name  (SAME)
...
signal.o: changed function: do_rt_tgsigqueueinfo
signal.o: changed function: do_rt_sigqueueinfo
signal.o: changed function: get_signal_to_deliver
signal.o: signal.o: changed section .rela__jump_table not selected for inclusion
signal.o: 1 unsupported section change(s)
/root/kpatch/kpatch-build/create-diff-object: unreconcilable difference

but then I hit change in jump_table, which looks unsupported at the moment, according to commit 1622123.
@jstancek
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Here is simpler reproducer, with base kernel containing kernel/test3.c with content:

#include <linux/init.h>
#include <linux/export.h>

static int dummy;

void test_function30(void)
{
    dummy = 1;
}

void test_function31(void)
{
    dummy = 2;
}

EXPORT_SYMBOL(test_function30);
EXPORT_SYMBOL(test_function31);

and kpatch patch:

diff --git a/kernel/test3.c b/kernel/test3.c
index 50d3c86..91a43a1 100644
--- a/kernel/test3.c
+++ b/kernel/test3.c
@@ -5,7 +5,9 @@ static int dummy;

 void test_function30(void)
 {
-   dummy = 1;
+   int i;
+   for (i = 0; i < 10; i++)
+       dummy += i;
 }

 void test_function31(void)
# /usr/local/libexec/kpatch/create-diff-object orig/kernel/test3.o patched/kernel/test3.o /root/vmlinux output/kernel/test3.o
=== section list (22) ===
ndx 01, type: 1, data (nil), size 0, name .text
ndx 02, type: 1, data 0x7fd4e9fff040, size 21, name .text.test_function30
ndx 03, type: 4, data 0x7fd4e9fffb88, size 48, name .rela.text.test_function30
ndx 04, type: 1, data 0x7fd4e9fff060, size 21, name .text.test_function31
ndx 05, type: 4, data 0x7fd4e9fffbb8, size 48, name .rela.text.test_function31
ndx 06, type: 1, data 0x7fd4e9fff080, size 16, name ___ksymtab+test_function31
ndx 07, type: 4, data 0x7fd4e9fffbe8, size 48, name .rela___ksymtab+test_function31
ndx 08, type: 1, data 0x7fd4e9fff090, size 32, name __ksymtab_strings
ndx 09, type: 1, data 0x7fd4e9fff0b0, size 8, name ___kcrctab+test_function31
ndx 10, type: 4, data 0x7fd4e9fffc18, size 24, name .rela___kcrctab+test_function31
ndx 11, type: 1, data 0x7fd4e9fff0c0, size 16, name ___ksymtab+test_function30
ndx 12, type: 4, data 0x7fd4e9fffc30, size 48, name .rela___ksymtab+test_function30
ndx 13, type: 1, data 0x7fd4e9fff0d0, size 8, name ___kcrctab+test_function30
ndx 14, type: 4, data 0x7fd4e9fffc60, size 24, name .rela___kcrctab+test_function30
ndx 15, type: 1, data (nil), size 0, name .data
ndx 16, type: 8, data (nil), size 0, name .bss
ndx 17, type: 8, data (nil), size 4, name .bss.dummy
ndx 18, type: 1, data 0x7fd4e9fff0d8, size 46, name .comment
ndx 19, type: 1, data (nil), size 0, name .note.GNU-stack
ndx 20, type: 3, data 0x7fd4e9fff106, size 280, name .shstrtab
ndx 21, type: 2, data 0x7fd4e9fff7e0, size 672, name .symtab
ndx 22, type: 3, data 0x7fd4e9fffa80, size 258, name .strtab

=== symbol list (28 entries) ===
sym 00, type 0, bind 0, ndx 00, name 
sym 01, type 3, bind 0, ndx 08, name __ksymtab_strings -> __ksymtab_strings
sym 02, type 3, bind 0, ndx 17, name .bss.dummy -> .bss.dummy
sym 03, type 4, bind 0, ndx 65521, name test3.c
sym 04, type 1, bind 0, ndx 17, name dummy -> .bss.dummy
sym 05, type 1, bind 0, ndx 06, name __ksymtab_test_function31 -> ___ksymtab+test_function31
sym 06, type 1, bind 0, ndx 08, name __kstrtab_test_function31 -> __ksymtab_strings
sym 07, type 1, bind 0, ndx 09, name __kcrctab_test_function31 -> ___kcrctab+test_function31
sym 08, type 1, bind 0, ndx 11, name __ksymtab_test_function30 -> ___ksymtab+test_function30
sym 09, type 1, bind 0, ndx 08, name __kstrtab_test_function30 -> __ksymtab_strings
sym 10, type 1, bind 0, ndx 13, name __kcrctab_test_function30 -> ___kcrctab+test_function30
sym 11, type 4, bind 0, ndx 65521, name 
sym 12, type 3, bind 0, ndx 01, name .text -> .text
sym 13, type 3, bind 0, ndx 02, name .text.test_function30 -> .text.test_function30
sym 14, type 3, bind 0, ndx 04, name .text.test_function31 -> .text.test_function31
sym 15, type 3, bind 0, ndx 06, name ___ksymtab+test_function31 -> ___ksymtab+test_function31
sym 16, type 3, bind 0, ndx 09, name ___kcrctab+test_function31 -> ___kcrctab+test_function31
sym 17, type 3, bind 0, ndx 11, name ___ksymtab+test_function30 -> ___ksymtab+test_function30
sym 18, type 3, bind 0, ndx 13, name ___kcrctab+test_function30 -> ___kcrctab+test_function30
sym 19, type 3, bind 0, ndx 15, name .data -> .data
sym 20, type 3, bind 0, ndx 16, name .bss -> .bss
sym 21, type 3, bind 0, ndx 18, name .comment -> .comment
sym 22, type 3, bind 0, ndx 19, name .note.GNU-stack -> .note.GNU-stack
sym 23, type 2, bind 1, ndx 04, name test_function31 -> .text.test_function31
sym 24, type 0, bind 1, ndx 65521, name __crc_test_function30
sym 25, type 0, bind 1, ndx 00, name __fentry__
sym 26, type 0, bind 1, ndx 65521, name __crc_test_function31
sym 27, type 2, bind 1, ndx 02, name test_function30 -> .text.test_function30

=== rela list for .text.test_function30 (2 entries) ===
offset 1, type 0, __fentry__ - 4
offset 8, type 2, .bss.dummy - 8

=== rela list for .text.test_function31 (2 entries) ===
offset 1, type 0, __fentry__ - 4
offset 8, type 2, .bss.dummy - 8

=== rela list for ___ksymtab+test_function31 (2 entries) ===
offset 0, type 1, test_function31 + 0
offset 8, type 1, __ksymtab_strings + 0

=== rela list for ___kcrctab+test_function31 (1 entries) ===
offset 0, type 1, __crc_test_function31 + 0

=== rela list for ___ksymtab+test_function30 (2 entries) ===
offset 0, type 1, test_function30 + 0
offset 8, type 1, __ksymtab_strings + 16

=== rela list for ___kcrctab+test_function30 (1 entries) ===
offset 0, type 1, __crc_test_function30 + 0
=== section list (22) ===
ndx 01, type: 1, data (nil), size 0, name .text
ndx 02, type: 1, data 0x7fd4e9ffd040, size 42, name .text.test_function30
ndx 03, type: 4, data 0x7fd4e9ffdb98, size 72, name .rela.text.test_function30
ndx 04, type: 1, data 0x7fd4e9ffd070, size 21, name .text.test_function31
ndx 05, type: 4, data 0x7fd4e9ffdbe0, size 48, name .rela.text.test_function31
ndx 06, type: 1, data 0x7fd4e9ffd090, size 16, name ___ksymtab+test_function31
ndx 07, type: 4, data 0x7fd4e9ffdc10, size 48, name .rela___ksymtab+test_function31
ndx 08, type: 1, data 0x7fd4e9ffd0a0, size 32, name __ksymtab_strings
ndx 09, type: 1, data 0x7fd4e9ffd0c0, size 8, name ___kcrctab+test_function31
ndx 10, type: 4, data 0x7fd4e9ffdc40, size 24, name .rela___kcrctab+test_function31
ndx 11, type: 1, data 0x7fd4e9ffd0d0, size 16, name ___ksymtab+test_function30
ndx 12, type: 4, data 0x7fd4e9ffdc58, size 48, name .rela___ksymtab+test_function30
ndx 13, type: 1, data 0x7fd4e9ffd0e0, size 8, name ___kcrctab+test_function30
ndx 14, type: 4, data 0x7fd4e9ffdc88, size 24, name .rela___kcrctab+test_function30
ndx 15, type: 1, data (nil), size 0, name .data
ndx 16, type: 8, data (nil), size 0, name .bss
ndx 17, type: 8, data (nil), size 4, name .bss.dummy
ndx 18, type: 1, data 0x7fd4e9ffd0e8, size 46, name .comment
ndx 19, type: 1, data (nil), size 0, name .note.GNU-stack
ndx 20, type: 3, data 0x7fd4e9ffd116, size 280, name .shstrtab
ndx 21, type: 2, data 0x7fd4e9ffd7f0, size 672, name .symtab
ndx 22, type: 3, data 0x7fd4e9ffda90, size 258, name .strtab

=== symbol list (28 entries) ===
sym 00, type 0, bind 0, ndx 00, name 
sym 01, type 3, bind 0, ndx 08, name __ksymtab_strings -> __ksymtab_strings
sym 02, type 3, bind 0, ndx 17, name .bss.dummy -> .bss.dummy
sym 03, type 4, bind 0, ndx 65521, name test3.c
sym 04, type 1, bind 0, ndx 17, name dummy -> .bss.dummy
sym 05, type 1, bind 0, ndx 06, name __ksymtab_test_function31 -> ___ksymtab+test_function31
sym 06, type 1, bind 0, ndx 08, name __kstrtab_test_function31 -> __ksymtab_strings
sym 07, type 1, bind 0, ndx 09, name __kcrctab_test_function31 -> ___kcrctab+test_function31
sym 08, type 1, bind 0, ndx 11, name __ksymtab_test_function30 -> ___ksymtab+test_function30
sym 09, type 1, bind 0, ndx 08, name __kstrtab_test_function30 -> __ksymtab_strings
sym 10, type 1, bind 0, ndx 13, name __kcrctab_test_function30 -> ___kcrctab+test_function30
sym 11, type 4, bind 0, ndx 65521, name 
sym 12, type 3, bind 0, ndx 01, name .text -> .text
sym 13, type 3, bind 0, ndx 02, name .text.test_function30 -> .text.test_function30
sym 14, type 3, bind 0, ndx 04, name .text.test_function31 -> .text.test_function31
sym 15, type 3, bind 0, ndx 06, name ___ksymtab+test_function31 -> ___ksymtab+test_function31
sym 16, type 3, bind 0, ndx 09, name ___kcrctab+test_function31 -> ___kcrctab+test_function31
sym 17, type 3, bind 0, ndx 11, name ___ksymtab+test_function30 -> ___ksymtab+test_function30
sym 18, type 3, bind 0, ndx 13, name ___kcrctab+test_function30 -> ___kcrctab+test_function30
sym 19, type 3, bind 0, ndx 15, name .data -> .data
sym 20, type 3, bind 0, ndx 16, name .bss -> .bss
sym 21, type 3, bind 0, ndx 18, name .comment -> .comment
sym 22, type 3, bind 0, ndx 19, name .note.GNU-stack -> .note.GNU-stack
sym 23, type 2, bind 1, ndx 04, name test_function31 -> .text.test_function31
sym 24, type 0, bind 1, ndx 65521, name __crc_test_function30
sym 25, type 0, bind 1, ndx 00, name __fentry__
sym 26, type 0, bind 1, ndx 65521, name __crc_test_function31
sym 27, type 2, bind 1, ndx 02, name test_function30 -> .text.test_function30

=== rela list for .text.test_function30 (3 entries) ===
offset 1, type 0, __fentry__ - 4
offset 7, type 2, .bss.dummy - 4
offset 36, type 2, .bss.dummy - 4

=== rela list for .text.test_function31 (2 entries) ===
offset 1, type 0, __fentry__ - 4
offset 8, type 2, .bss.dummy - 8

=== rela list for ___ksymtab+test_function31 (2 entries) ===
offset 0, type 1, test_function31 + 0
offset 8, type 1, __ksymtab_strings + 0

=== rela list for ___kcrctab+test_function31 (1 entries) ===
offset 0, type 1, __crc_test_function31 + 0

=== rela list for ___ksymtab+test_function30 (2 entries) ===
offset 0, type 1, test_function30 + 0
offset 8, type 1, __ksymtab_strings + 16

=== rela list for ___kcrctab+test_function30 (1 entries) ===
offset 0, type 1, __crc_test_function30 + 0
section .text.test_function30 has changed
section .rela.text.test_function30 has changed
section .symtab has changed
test3.o: symbol info mismatch: 
/usr/local/libexec/kpatch/create-diff-object: unreconcilable difference

@sjenning
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I can't recreate the "symbol info mismatch" issue with the latest master 6aee215. I do get the:

signal.o: signal.o: changed section .rela__jump_table not selected for inclusion
signal.o: 1 unsupported section change(s)

which is being track in issue #157. Can you confirm?

@jstancek jstancek mentioned this issue May 27, 2014
Merged
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correlate symbols also by type jstancek/kpatch
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@sjenning @jstancek