https://bugs.kde.org/show_bug.cgi?id=454925
Bug ID: 454925
Summary: Stracktraces contain addresses that are off by one,
except frame 0
Product: valgrind
Version: unspecified
Platform: Debian stable
OS: Linux
Status: REPORTED
Severity: minor
Priority: NOR
Component: general
Assignee: jsew...@acm.org
Reporter: bernha...@mailbox.org
Target Milestone: ---
Created attachment 149505
--> https://bugs.kde.org/attachment.cgi?id=149505&action=edit
Attempt-to-fix-EIP-pointer-in-stacktrace.patch
The addresses in stacktraces shown by valgrind are off by one, except for frame
0.
This seems to be explained in this commit:
https://sourceware.org/git/?p=valgrind.git;a=patch;f=coregrind/m_stacktrace.c;h=efaaa0b74a695a68ef5e758102d3fe3920e121fd
So valgrind is decrementing the address by one to get into the call
instruction.
But when showing the stacktrace this decremention gets not corrected later.
Below example shows the same process, one with the valgrind stacktrace and one
with the gdb stacktrace.
A disassemble shows valgrind's address in the last byte of the call
instruction, while
gdb shows the next byte, the return address of the call instruction.
$ valgrind --vgdb=yes --vgdb-error=0 rc
==4357== Invalid free() / delete / delete[] / realloc()
==4357== at 0x4840EB7: free (vg_replace_malloc.c:872)
==4357== by 0x1134BF: ??? (in /usr/bin/rc.byron)
==4357== by 0x118B7C: ??? (in /usr/bin/rc.byron)
==4357== by 0x118473: ??? (in /usr/bin/rc.byron)
==4357== by 0x486F6E5: rl_completion_matches (in
/usr/lib/i386-linux-gnu/libreadline.so.8.1)
==4357== by 0x118760: ??? (in /usr/bin/rc.byron)
...
$ gdb $(which rc)
(gdb) target remote | /usr/bin/vgdb --pid=4357
(gdb) cont
(gdb) bt
#0 0x04840eb7 in _vgr10050ZU_VgSoSynsomalloc_free (p=0x4b2e758) at
m_replacemalloc/vg_replace_malloc.c:872
#1 0x001134c0 in ?? ()
#2 0x00118b7d in ?? ()
#3 0x00118474 in ?? ()
#4 0x0486f6e6 in rl_completion_matches () from
/lib/i386-linux-gnu/libreadline.so.8
#5 0x00118761 in ?? ()
...
Dump of assembler code from 0x4840eb5 to 0x4840ebd:
0x04840eb5 <_vgr10050ZU_VgSoSynsomalloc_free+101>: 87 db xchg
%ebx,%ebx
0x04840eb7 <_vgr10050ZU_VgSoSynsomalloc_free+103>: 89 55 e0 mov
%edx,-0x20(%ebp)
0x04840eba <_vgr10050ZU_VgSoSynsomalloc_free+106>: 8b 45 e0 mov
-0x20(%ebp),%eax
End of assembler dump.
...
(gdb) disassemble /r 0x001134ba,0x001134c6
Dump of assembler code from 0x1134ba to 0x1134c6:
0x001134ba: 50 push %eax
0x001134bb: e8 c0 6b ff ff call 0x10a080 <free@plt>
0x001134c0: 83 c4 10 add $0x10,%esp
0x001134c3: 83 c4 08 add $0x8,%esp
End of assembler dump.
Attached patch is an attempt to correct just the output of the stacktrace in
`VG_(describe_IP)`
while leaving the internal used address unchanged.
SOFTWARE/OS VERSIONS
Linux:
valgrind 1:3.16.1-1 amd64 (Bullseye)
valgrind 1:3.18.1-1 i386 (Bookworm)
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