Bug 2227356
| Summary: | breakpoint in vandps instruction causes register clobber | ||||||
|---|---|---|---|---|---|---|---|
| Product: | Red Hat Enterprise Linux 8 | Reporter: | Paulo Andrade <pandrade> | ||||
| Component: | gdb | Assignee: | Keith Seitz <keiths> | ||||
| gdb sub component: | system-version | QA Contact: | qe-baseos-tools-bugs | ||||
| Status: | NEW --- | Docs Contact: | |||||
| Severity: | medium | ||||||
| Priority: | medium | CC: | gdb-bugs, hartsjc, ohudlick | ||||
| Version: | 8.6 | Keywords: | Triaged | ||||
| Target Milestone: | rc | ||||||
| Target Release: | --- | ||||||
| Hardware: | All | ||||||
| OS: | Linux | ||||||
| Whiteboard: | |||||||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | Type: | Bug | |||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Embargoed: | |||||||
| Attachments: |
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Any news? On a quick sampling with:
$ lldb -v
lldb version 13.0.1
it works, but failed will all gdb versions I tested.
$ lldb run
(lldb) target create "run"
Current executable set to '/home/pcpa/gdb_avx_issue/run' (x86_64).
(lldb) b test_func
Breakpoint 1: where = run`test_func [inlined] _mm256_and_ps at avxintrin.h:174:19, address = 0x0000000000401240
(lldb) r
Process 1489184 launched: '/home/pcpa/gdb_avx_issue/run' (x86_64)
Process 1489184 stopped
* thread #1, name = 'run', stop reason = breakpoint 1.1
frame #0: 0x0000000000401240 run`test_func [inlined] _mm256_and_ps(__B=([0] = -6.2598534E+18, [1] = -6.2598534E+18, [2] = -6.2598534E+18, [3] = -6.2598534E+18, [4] = -6.2598534E+18, [5] = -6.2598534E+18, [6] = -6.2598534E+18, [7] = -6.2598534E+18), __A=<unavailable>) at avxintrin.h:174:19
171 extern __inline __m256 __attribute__((__gnu_inline__, __always_inline__, __artificial__))
172 _mm256_and_ps (__m256 __A, __m256 __B)
173 {
-> 174 return (__m256) __builtin_ia32_andps256 ((__v8sf)__A, (__v8sf)__B);
175 }
176
177 extern __inline __m256d __attribute__((__gnu_inline__, __always_inline__, __artificial__))
(lldb) p $ymm0
(unsigned char __attribute__((ext_vector_type(32)))) $0 = (0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff)
(lldb) disassemble
run`test_func:
-> 0x401240 <+0>: vandps 0x6e18(%rip), %ymm0, %ymm0 ; constants + 16384
0x401248 <+8>: retq
(lldb) si
Process 1489184 stopped
* thread #1, name = 'run', stop reason = instruction step into
frame #0: 0x0000000000401248 run`test_func(x=<unavailable>) at test.c:13:1
10
11 __m256 test_func(__m256 x) {
12 return _mm256_and_ps(x, constants[512]);
-> 13 }
(lldb) p $ymm0
(unsigned char __attribute__((ext_vector_type(32)))) $1 = (0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde, 0xef, 0xbe, 0xad, 0xde)
(lldb) c
Process 1489184 resuming
Out 0: 0xdeadbeef
Out 1: 0xdeadbeef
Out 2: 0xdeadbeef
Out 3: 0xdeadbeef
Out 4: 0xdeadbeef
Out 5: 0xdeadbeef
Out 6: 0xdeadbeef
Out 7: 0xdeadbeef
Process 1489184 exited with status = 0 (0x00000000)
(lldb) q
I will be looking into this tomorrow. While I do not specifically have a solution for the problem, I can
offer two workarounds which should help until a proper solution is
developed.
1) Use gdbserver.
2) Disable displaced stepping (set displaced-stepping off).
[This can be added to a .gdbinit, e.g., or passed on command-line
with -ex or -iex.]
|
Created attachment 1980527 [details] gdb_avx_issue.tar Example reproducer: $ tar xf gdb_avx_issue.tar $ cd gdb_avx_issue/ $ ./build $ ./run Out 0: 0xdeadbeef Out 1: 0xdeadbeef Out 2: 0xdeadbeef Out 3: 0xdeadbeef Out 4: 0xdeadbeef Out 5: 0xdeadbeef Out 6: 0xdeadbeef Out 7: 0xdeadbeef Now in gdb: $ gdb run ... (gdb) b test_func Breakpoint 1 at 0x401240: file /usr/lib/gcc/x86_64-redhat-linux/11/include/avxintrin.h, line 174. (gdb) r ... Breakpoint 1, test_func (x=...) at test.c:12 12 return _mm256_and_ps(x, constants[512]); (gdb) c Continuing. Out 0: 0x00000000 Out 1: 0x00000000 Out 2: 0x00000000 Out 3: 0x00000000 Out 4: 0x00000000 Out 5: 0x00000000 Out 6: 0x00000000 Out 7: 0x00000000 This issue appears to happen not just in rhel8 but any other recent environment tested with different gdb major versions. For the reproducer, the issue appear to only happen if the breakpoint is in the vandps instruction, but probably might trigger in other instructions or conditions. (gdb) p $ymm0 $1 = {..., v8_int32 = {-1, -1, -1, -1, -1, -1, -1, -1}, ... } (gdb) watch $ymm0 Watchpoint 2: $ymm0 (gdb) disassemble Dump of assembler code for function test_func: => 0x0000000000401240 <+0>: vandps 0x6e18(%rip),%ymm0,%ymm0 # 0x408060 <constants+16384> 0x0000000000401248 <+8>: ret End of assembler dump. (gdb) si Watchpoint 2: $ymm0 Old value = {..., v8_int32 = {-1, -1, -1, -1, -1, -1, -1, -1}, ...} New value = {..., v8_int32 = {0, 0, 0, 0, 0, 0, 0, 0}, ...} 0x0000000000401248 in test_func (x=...) at test.c:18 18 }