Build errors with fuzz/x86_instruction_emulator harness

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Hello,

See the attached log snippet.  This is current staging, with a GCC 13
toolchain.

First of all, a minor issue.  Counting the number of
`-D__XEN_INTERFACE_VERSION__=__XEN_LATEST_INTERFACE_VERSION__`'s, we
have included CFLAGS on the CC line 4 times.  This is something that
appears to be in common with all of tools/ and is probably the primary
contributor to exceeding the Gitlab CI 4M log limit...

Next the error.  This doesn't build when CFLAGS coming in from the
packaging environment include `-flto=auto`.

Clearly our wrapping trick doesn't work with LTO, but it's not obvious why.

readelf -Wa tools/fuzz/x86_instruction_emulator/wrappers.o | grep emul_
  [223] .gnu.lto_emul_fwrite.38.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01c2ec 000194 00   E  0   0  1
  [224] .gnu.lto_emul_memcmp.39.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01c480 0001a7 00   E  0   0  1
  [225] .gnu.lto_emul_memcpy.40.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01c627 000175 00   E  0   0  1
  [226] .gnu.lto_emul_memset.41.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01c79c 000186 00   E  0   0  1
  [227] .gnu.lto_emul_printf.42.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01c922 0002cd 00   E  0   0  1
  [228] .gnu.lto_emul_putchar.43.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01cbef 000216 00   E  0   0  1
  [229] .gnu.lto_emul_puts.44.43da3a7fd30cc0a1 PROGBITS       
0000000000000000 01ce05 000180 00   E  0   0  1

shows that there's something relevant in the object file.

Manual poking about in the build environment indicates that
tools/tests/x86_instruction_emulator is similarly impacted.

Any ideas?

Obviously we can inhibit LTO for the x86_emul userspace, but that ought
to be a last resort.

~Andrew

Attachment: x86_insn_emul.log
Description: Text Data