[Bug build/31316] Fails test misc/tst-dirname "Didn't expect signal from child: got `Illegal instruction'" on non SSE CPUs

["fweimer at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31316

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com

--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
The instruction stream does not make sense.

Running this:

“
import base64
data="""8d 70 08 f7 c6 0f 00 00 00 0f 85 20 0a 00 00 8d 5c 97 04
65 a1 0c 00 00 00 85 c0 0f 85 46 04 00 00 8b 4c 24 18 89 f0 c1 e8 0c 8b 79 08
8b 4c 24 14 31 f8 89 41 04 8b 44 24 18 8b 40 04 89 44 24
""".replace(' ', '').replace('\n', '')
with open('f', 'wb') as out:
    out.write(base64.b16decode(data, casefold=True))
”

And: objdump -b binary -m i386 -D f

gives:

   0:   8d 70 08                lea    0x8(%eax),%esi
   3:   f7 c6 0f 00 00 00       test   $0xf,%esi
   9:   0f 85 20 0a 00 00       jne    0xa2f
   f:   8d 5c 97 04             lea    0x4(%edi,%edx,4),%ebx
  13:   65 a1 0c 00 00 00       mov    %gs:0xc,%eax
  19:   85 c0                   test   %eax,%eax
  1b:   0f 85 46 04 00 00       jne    0x467
  21:   8b 4c 24 18             mov    0x18(%esp),%ecx
  25:   89 f0                   mov    %esi,%eax
  27:   c1 e8 0c                shr    $0xc,%eax
  2a:   8b 79 08                mov    0x8(%ecx),%edi
  2d:   8b 4c 24 14             mov    0x14(%esp),%ecx
  31:   31 f8                   xor    %edi,%eax
  33:   89 41 04                mov    %eax,0x4(%ecx)
  36:   8b 44 24 18             mov    0x18(%esp),%eax
  3a:   8b 40 04                mov    0x4(%eax),%eax
  3d:   89                      .byte 0x89
  3e:   44                      inc    %esp
  3f:   24                      .byte 0x24

The fault is at offset 0x2a, which is as far as I can see a perfectly fine i386
instruction. It's also not in a string function, the instruction sequence
involving %gs is related to a single-thread optimization. The tail involving
inc %esp is also really dubious.

Could you obtain a backtrace using GDB, possibly from a coredump?

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