https://bugs.kde.org/show_bug.cgi?id=489088
Bug ID: 489088
Summary: Valgrind throws unhandled instruction bytes: 0xC5 0x79
0xD6 0xE0 0xC5 0xFA 0x7E 0xDB 0xC5 0xF8
Classification: Developer tools
Product: valgrind
Version: 3.24 GIT
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: vex
Assignee: jsew...@acm.org
Reporter: s...@gentoo.org
Target Milestone: ---
Created attachment 170894
--> https://bugs.kde.org/attachment.cgi?id=170894&action=edit
test.c
I hit the following when reducing a possible GCC bug
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115533).
At points during my reduction of a test from flac, I got the following:
```
$ gcc-15 test.c -o foo -O3 -ggdb3 -march=native -fipa-pta -fno-vect-cost-model
&& valgrind ./foo
==2627495== Memcheck, a memory error detector
==2627495== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==2627495== Using Valgrind-3.24.0.GIT and LibVEX; rerun with -h for copyright
info
==2627495== Command: ./foo
==2627495==
vex amd64->IR: unhandled instruction bytes: 0xC5 0x79 0xD6 0xE0 0xC5 0xFA 0x7E
0xDB 0xC5 0xF8
vex amd64->IR: REX=0 REX.W=0 REX.R=1 REX.X=0 REX.B=0
vex amd64->IR: VEX=1 VEX.L=0 VEX.nVVVV=0x0 ESC=0F
vex amd64->IR: PFX.66=1 PFX.F2=0 PFX.F3=0
==2627495== valgrind: Unrecognised instruction at address 0x109e00.
==2627495== at 0x109E00: filter (test.c:64)
==2627495== by 0x109E00: AnalyzeSamples (test.c:100)
==2627495== by 0x109366: main (test.c:167)
==2627495== Your program just tried to execute an instruction that Valgrind
==2627495== did not recognise. There are two possible reasons for this.
==2627495== 1. Your program has a bug and erroneously jumped to a non-code
==2627495== location. If you are running Memcheck and you just saw a
==2627495== warning about a bad jump, it's probably your program's fault.
==2627495== 2. The instruction is legitimate but Valgrind doesn't handle it,
==2627495== i.e. it's Valgrind's fault. If you think this is the case or
==2627495== you are not sure, please let us know and we'll try to fix it.
==2627495== Either way, Valgrind will now raise a SIGILL signal which will
==2627495== probably kill your program.
==2627495==
==2627495== Process terminating with default action of signal 4 (SIGILL):
dumping core
==2627495== Illegal opcode at address 0x109E00
==2627495== at 0x109E00: filter (test.c:64)
==2627495== by 0x109E00: AnalyzeSamples (test.c:100)
==2627495== by 0x109366: main (test.c:167)
```
It's possible that the program was just jumping to genuine junk, but I thought
I'd report it on the off-chance it isn't.
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