Provide syscall wrappers for mmap and munmap
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We have to support targets other than GNU/Linux. Embedded GNU libc calls with Linux kernel bindings is not going to fly. |
please point me how to make this portable then. thanks |
bertwesarg
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bregma
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Apr 2, 2023
include/libunwind_i.h
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| @@ -58,6 +58,8 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ | |||
| #include <errno.h> | |||
| #include <stdio.h> | |||
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| #include <sys/syscall.h> /* For SYS_xxx definitions */ | |||
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This non-portable header needs to be surrounded with an #if defined(HAVE_SYS_SYSCALL_H).
This improves the AS-safety, because `munmap` may be intercepted and call not AS-safe functions (e.g., malloc), which then leads to deadlocks. (see Open MPI in the past or UCX)
Libunwind assumes that `mmap` "goes straight through to a system call stub". But this might not be true as other runtimes (I'm looking at you UCX) wrap `mmap` and do AS-unsafe stuff again.
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These functions are assumed to be direct wrappers to the syscalls, but in the past (see Open MPI) and also now (see UCX) runtimes do intercept these functions and do AS-unsafe stuff inside there runtimes. Hence provide internal syscall wrappers for these functions to improve AS-safety.