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Subject: [Bug target/102952] New code-gen options for retpolines and straight
 line speculation
Date: Wed, 27 Oct 2021 22:12:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102952

--- Comment #14 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to peterz from comment #13)
> (In reply to H.J. Lu from comment #12)
> > (In reply to peterz from comment #9)
> > > Created attachment 51683 [details]
> > > kernel patch to test -mharden-sls=3Dall
> > >=20
> > > $ make O=3Ddefconfig CC=3Dgcc-12.0.0 arch/x86/entry/common.o
> > > ...
> > > arch/x86/entry/common.o: warning: objtool: do_SYSENTER_32()+0x1b:
> > > unreachable instruction
> >=20
> > Please try the v2 patch.
>=20
> Per comment #6 this should be v3, no? Anyway, the good news is that I now
> seem to have a kernel image with lots of extra int3 instructions, but all=
 in
> the right place.
>=20
> *However*, I seem to be missing a few:
>=20
>   36f4:       41 5f                   pop    %r15
>   36f6:       e9 00 00 00 00          jmp    36fb
> <__do_set_cpus_allowed+0x5b>
>         36f7: R_X86_64_PLT32    __x86_indirect_thunk_rax-0x4

This is a direct branch.

>   36fb:       48 8b 87 90 02 00 00    mov    0x290(%rdi),%rax
>=20
> There should be one after the jmp __x86_indirect_thunk_* thingy. I'll do =
an
> objtool patch to search for missing int3, but that'll have to wait until
> tomorrow, it's past midnight.=