Re: [Valgrind-users] Need support in debugging Valgrind 3.18 glibc segv error

[Paul F. <pj...@wa...>]

On 3/12/25 22:40, kiran hardas wrote:
> Hi Philippe/Team,
>
> Thank you Philippe for your suggestions, I was able to resolve the 
> earlier errors by adding additional valgrind options and loading the 
> symbol table.
> In my application, few variables and a function pointer was 
> uninitialised which led to previous errors mentioned in earlier email.
>
> Proceeding further with my earlier activity, right now i am 
> seeing error related to unhandled syscall no. 395 in valgrind logs. I 
> thought to bring this up in this mail chain for your suggestions/inputs.
>
>
> # ./usr/test/bin/valgrind --version -v
> valgrind-3.24.0-fcdaa47426-20241101
>
> GNU/Linux 5.4
> Glibc 2.40
> gcc 14.2
> binutils 2.43
>
>
> Error snippet:
>
> --6423-- WARNING: unhandled x86-linux syscall: 395
> ==6423==    at 0x1F757398: shmget (in /lib/libc-2.40.so 
> <http://libc-2.40.so>)
> by 0xF597083: <application backtraces>
> ...
> ...
> --6423-- You may be able to write your own handler.
> --6423-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
> --6423-- Nevertheless we consider this a bug.  Please report
> --6423-- it at http://valgrind.org/support/bug_reports.html.
>
> From my analysis of valgrind code, i can see the shmget wrappers are 
> present in coregrind/m_syswrap area, but still it is throwing such error.
>
> Any pointers or suggestions would be appreciated, Thanks.
>
Hi

That looks like shmget on x86. Can you confirm that?

If so could you build valgrind with this patch

diff --git a/coregrind/m_syswrap/syswrap-x86-linux.c 
b/coregrind/m_syswrap/syswrap-x86-l
inux.c
index 50384817d..5c0b57789 100644
--- a/coregrind/m_syswrap/syswrap-x86-linux.c
+++ b/coregrind/m_syswrap/syswrap-x86-linux.c
@@ -1621,6 +1621,8 @@static SyscallTableEntry syscall_table[] = {

    GENX_(__NR_rseq,              sys_ni_syscall),       // 386

+   LINX_(__NR_shmget,            sys_shmget),           // 395
+
    LINXY(__NR_clock_gettime64,   sys_clock_gettime64),  // 403
    LINX_(__NR_clock_settime64,   sys_clock_settime64),  // 404


and let us know if it works?

It's likely that you will also need shmat shmctl and shmdt as well.

A+

Paul