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: | CLOSED MIGRATED | Docs Contact: | |||||
| Severity: | medium | ||||||
| Priority: | medium | CC: | gdb-bugs, hartsjc, ohudlick | ||||
| Version: | 8.6 | Keywords: | MigratedToJIRA, Triaged | ||||
| Target Milestone: | rc | Flags: | pm-rhel:
mirror+
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| 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: | 2023-09-22 16:00:37 UTC | 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.]
Issue migration from Bugzilla to Jira is in process at this time. This will be the last message in Jira copied from the Bugzilla bug. This BZ has been automatically migrated to the issues.redhat.com Red Hat Issue Tracker. All future work related to this report will be managed there. Due to differences in account names between systems, some fields were not replicated. Be sure to add yourself to Jira issue's "Watchers" field to continue receiving updates and add others to the "Need Info From" field to continue requesting information. To find the migrated issue, look in the "Links" section for a direct link to the new issue location. The issue key will have an icon of 2 footprints next to it, and begin with "RHEL-" followed by an integer. You can also find this issue by visiting https://issues.redhat.com/issues/?jql= and searching the "Bugzilla Bug" field for this BZ's number, e.g. a search like: "Bugzilla Bug" = 1234567 In the event you have trouble locating or viewing this issue, you can file an issue by sending mail to rh-issues. You can also visit https://access.redhat.com/articles/7032570 for general account information. |
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 }