Re: Need support in debugging Valgrind 3.18 glibc segv error

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Hi Paul/Team,

Thank you for your suggestion. I added the entry for shmget function in
coregrind/m_syswrap/syswrap-x86-linux.c
and the error got resolved for shmget function. Yes it is x86 linux that
is getting used. Similar errors came for shmat, shmdt, shmctl functions.
I added similar entries of those functions too in the table and resolved
the errors.

Currently i am getting error from shmat function as "Invalid argument" from
my application code.
The data pointer returned by shmat function is coming as 0xffffffff which
is -1 (error). I am calling the shmat as below
 in my application code

data =3D shmat(shmid, NULL, 0);            /* where data is a struct pointe=
r
and shmid is 1 obtained by a successful shmget call */

I verified the arguments for this shmat function and they seem to be fine.
Also checked for permission issues.
I am suspecting memory issue which could be resulting in shmat attach
failure after running valgrind (have glibc 2.40).

Would appreciate any advice/suggestion you can provide for this issue.

Thanks in advance

On Sun, Mar 16, 2025 at 1:47=E2=80=AFAM Paul Floyd via Valgrind-users <
[email protected]> wrote:

>
> 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
> > =3D=3D6423=3D=3D    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 erro=
r.
> >
> > 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[] =3D {
>
>     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
>
>
>
>
> _______________________________________________
> Valgrind-users mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/valgrind-users
>

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<div dir=3D"ltr">Hi Paul/Team,<div><br></div><div>Thank you for your sugges=
tion. I added the entry for shmget function in coregrind/m_syswrap/syswrap-=
x86-linux.c</div><div>and the error got resolved for shmget function. Yes i=
t is x86 linux that is=C2=A0getting used. Similar errors came for shmat, sh=
mdt, shmctl functions.</div><div>I added similar entries of those functions=
 too in the table and resolved the=C2=A0errors.=C2=A0</div><div><br></div><=
div>Currently i am getting error from shmat function as &quot;Invalid argum=
ent&quot; from my application code.</div><div>The data pointer returned by =
shmat function is coming as 0xffffffff which is -1 (error). I am calling th=
e shmat as below</div><div>=C2=A0in my application code</div><div><br></div=
><div>data =3D shmat(shmid, NULL, 0);=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 /* where data is a struct pointer and shmid is 1 obtained by a successf=
ul=C2=A0shmget call */</div><div><br></div><div>I verified the arguments fo=
r this shmat function and they seem to be fine. Also checked for permission=
 issues.</div><div>I am suspecting memory issue which could be resulting in=
 shmat attach failure after running valgrind (have glibc 2.40).</div><div><=
br></div><div>Would appreciate any advice/suggestion you can provide for th=
is issue.</div><div><br></div><div>Thanks in advance</div></div><br><div cl=
ass=3D"gmail_quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_a=
ttr">On Sun, Mar 16, 2025 at 1:47=E2=80=AFAM Paul Floyd via Valgrind-users =
&lt;<a href=3D"mailto:[email protected]">valgrind-users@=
lists.sourceforge.net</a>&gt; wrote:<br></div><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,20=
4);padding-left:1ex"><br>
On 3/12/25 22:40, kiran hardas wrote:<br>
&gt; Hi=C2=A0Philippe/Team,<br>
&gt;<br>
&gt; Thank you Philippe for your suggestions, I was able=C2=A0to resolve th=
e <br>
&gt; earlier errors by adding additional valgrind options and loading the <=
br>
&gt; symbol table.<br>
&gt; In my application, few variables and a function pointer was <br>
&gt; uninitialised which led to previous errors mentioned=C2=A0in earlier=
=C2=A0email.<br>
&gt;<br>
&gt; Proceeding further with my earlier activity, right now i am <br>
&gt; seeing=C2=A0error related to unhandled syscall no. 395 in valgrind log=
s. I <br>
&gt; thought to bring this up in this mail chain for your suggestions/input=
s.<br>
&gt;<br>
&gt;<br>
&gt; # ./usr/test/bin/valgrind --version -v<br>
&gt; valgrind-3.24.0-fcdaa47426-20241101<br>
&gt;<br>
&gt; GNU/Linux 5.4<br>
&gt; Glibc 2.40<br>
&gt; gcc 14.2<br>
&gt; binutils 2.43<br>
&gt;<br>
&gt;<br>
&gt; Error snippet:<br>
&gt;<br>
&gt; --6423-- WARNING: unhandled x86-linux syscall: 395<br>
&gt; =3D=3D6423=3D=3D =C2=A0 =C2=A0at 0x1F757398: shmget (in /lib/<a href=
=3D"http://libc-2.40.so" rel=3D"noreferrer" target=3D"_blank">libc-2.40.so<=
/a> <br>
&gt; &lt;<a href=3D"http://libc-2.40.so" rel=3D"noreferrer" target=3D"_blan=
k">http://libc-2.40.so</a>&gt;)<br>
&gt; by 0xF597083: &lt;application backtraces&gt;<br>
&gt; ...<br>
&gt; ...<br>
&gt; --6423-- You may be able to write your own handler.<br>
&gt; --6423-- Read the file README_MISSING_SYSCALL_OR_IOCTL.<br>
&gt; --6423-- Nevertheless we consider this a bug.=C2=A0 Please report<br>
&gt; --6423-- it at <a href=3D"http://valgrind.org/support/bug_reports.html=
" rel=3D"noreferrer" target=3D"_blank">http://valgrind.org/support/bug_repo=
rts.html</a>.<br>
&gt;<br>
&gt; From my analysis of valgrind code, i can see the shmget wrappers are <=
br>
&gt; present in coregrind/m_syswrap area, but still it is throwing such err=
or.<br>
&gt;<br>
&gt; Any pointers or suggestions would be appreciated, Thanks.<br>
&gt;<br>
Hi<br>
<br>
That looks like shmget on x86. Can you confirm that?<br>
<br>
If so could you build valgrind with this patch<br>
<br>
diff --git a/coregrind/m_syswrap/syswrap-x86-linux.c <br>
b/coregrind/m_syswrap/syswrap-x86-l<br>
inux.c<br>
index 50384817d..5c0b57789 100644<br>
--- a/coregrind/m_syswrap/syswrap-x86-linux.c<br>
+++ b/coregrind/m_syswrap/syswrap-x86-linux.c<br>
@@ -1621,6 +1621,8 @@static SyscallTableEntry syscall_table[] =3D {<br>
<br>
=C2=A0=C2=A0=C2=A0=C2=A0GENX_(__NR_rseq, =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sys_ni_syscall), =C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0// 386<br>
<br>
+ =C2=A0=C2=A0LINX_(__NR_shmget, =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0sys_shmget), =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0// 395<br>
+<br>
=C2=A0=C2=A0=C2=A0=C2=A0LINXY(__NR_clock_gettime64, =C2=A0=C2=A0sys_clock_g=
ettime64), =C2=A0// 403<br>
=C2=A0=C2=A0=C2=A0=C2=A0LINX_(__NR_clock_settime64, =C2=A0=C2=A0sys_clock_s=
ettime64), =C2=A0// 404<br>
<br>
<br>
and let us know if it works?<br>
<br>
It&#39;s likely that you will also need shmat shmctl and shmdt as well.<br>
<br>
A+<br>
<br>
Paul<br>
<br>
<br>
<br>
<br>
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=3D"noreferrer" target=3D"_blank">https://lists.sourceforge.net/lists/listi=
nfo/valgrind-users</a><br>
</blockquote></div>

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