https://bugs.kde.org/show_bug.cgi?id=492923
Bug ID: 492923
Summary: amd64: `xchg ax, r16` mistakenly clears rax[63:16]
Classification: Developer tools
Product: valgrind
Version: 3.23 GIT
Platform: Other
OS: All
Status: REPORTED
Severity: normal
Priority: NOR
Component: vex
Assignee: jsew...@acm.org
Reporter: cont...@mborgerson.com
Target Milestone: ---
Created attachment 173510
--> https://bugs.kde.org/attachment.cgi?id=173510&action=edit
Patch
SUMMARY
On current Valgrind (VALGRIND_3_23_0-107-g1a1343b13), the translation for `xchg
ax, r16` will mistakenly clear rax[63:16]. Attached patch corrects the issue.
STEPS TO REPRODUCE
The following test program demonstrates this issue:
```c
// gcc -o test_xchg_ax_dx test_xchg_ax_dx.c
#include <stdint.h>
#include <stdio.h>
#include <assert.h>
int main(int argc, char const *argv[])
{
uint64_t rax = 0xfbcadd99fbca7654;
uint64_t rdx = 0x1234fdb512345678;
asm volatile (
"xchg %%ax, %%dx;"
: "=a"(rax), "=d"(rdx)
: "a"(rax), "d"(rdx)
);
printf("rax = %016lx, rdx = %016lx\n", rax, rdx);
assert(rax == 0xfbcadd99fbca5678);
assert(rdx == 0x1234fdb512347654);
return 0;
}
```
OBSERVED RESULT
```
matt@iron:~/valgrind-src$ ./bin/valgrind ./test_xchg_ax_dx
==61465== Memcheck, a memory error detector
==61465== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==61465== Using Valgrind-3.24.0.GIT and LibVEX; rerun with -h for copyright
info
==61465== Command: ./test_xchg_ax_dx
==61465==
rax = 0000000000005678, rdx = 1234fdb512347654
test_xchg_ax_dx: test_xchg_ax_dx.c:15: main: Assertion `rax ==
0xfbcadd99fbca5678' failed.
==61465==
==61465== Process terminating with default action of signal 6 (SIGABRT)
==61465== at 0x4912B1C: __pthread_kill_implementation (pthread_kill.c:44)
==61465== by 0x4912B1C: __pthread_kill_internal (pthread_kill.c:78)
==61465== by 0x4912B1C: pthread_kill@@GLIBC_2.34 (pthread_kill.c:89)
==61465== by 0x48B926D: raise (raise.c:26)
==61465== by 0x489C8FE: abort (abort.c:79)
==61465== by 0x489C81A: __assert_fail_base.cold (assert.c:94)
==61465== by 0x48AF506: __assert_fail (assert.c:103)
==61465== by 0x109200: main (in /home/matt/valgrind-src/test_xchg_ax_dx)
==61465==
==61465== HEAP SUMMARY:
==61465== in use at exit: 1,024 bytes in 1 blocks
==61465== total heap usage: 6 allocs, 5 frees, 2,972 bytes allocated
==61465==
==61465== LEAK SUMMARY:
==61465== definitely lost: 0 bytes in 0 blocks
==61465== indirectly lost: 0 bytes in 0 blocks
==61465== possibly lost: 0 bytes in 0 blocks
==61465== still reachable: 1,024 bytes in 1 blocks
==61465== suppressed: 0 bytes in 0 blocks
==61465== Rerun with --leak-check=full to see details of leaked memory
==61465==
==61465== For lists of detected and suppressed errors, rerun with: -s
==61465== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Aborted
```
EXPECTED RESULT
```
matt@iron:~/valgrind-src$ ./test_xchg_ax_dx
rax = fbcadd99fbca5678, rdx = 1234fdb512347654
```
SOFTWARE/OS VERSIONS
Windows:
macOS:
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma:
KDE Plasma Version:
KDE Frameworks Version:
Qt Version:
ADDITIONAL INFORMATION
Issue originally reported to angr at https://github.com/angr/angr/issues/3878
by mnd-c.
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