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SubjectRe: [PATCH 1/1] x86/speculation, objtool: Annotate indirect calls/jumps for objtool on 32bit

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Mar 14, 2018 at 11:24:27AM +0000, Andy Whitcroft wrote:
> > In 9e0e3c5130e9 ("x86/speculation, objtool: Annotate indirect calls/jumps
> > for objtool") we added annotations for CALL_NOSPEC/JMP_NOSPEC on x86 64bit.
> > We did not annotate the 32bit path. Annotate it similarly.
> >
> > Signed-off-by: Andy Whitcroft <apw@canonical.com>
> > ---
> > arch/x86/include/asm/nospec-branch.h | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > While reviewing indirect calls in our builds I noted that the
> > i386 retpoline CALL_NOSPEC is not annotated safe even though
> > its amd64 equivalent is. I cannot see any reason this is not
> > also inherantly safe. Peter was there a reason that you did
> > not annotate this one too? Anyhow, on the assumption this was
> > just missed, this patch annotates it.
>
> Yeah, just an oversight aided by the fact that I (obviously) never build
> 32bit kernels.
>
> > diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> > index d0dabeae0505..07886162bdf8 100644
> > --- a/arch/x86/include/asm/nospec-branch.h
> > +++ b/arch/x86/include/asm/nospec-branch.h
> > @@ -183,7 +183,10 @@
> > * otherwise we'll run out of registers. We don't care about CET
> > * here, anyway.
> > */
> > -# define CALL_NOSPEC ALTERNATIVE("call *%[thunk_target]\n", \
> > +# define CALL_NOSPEC \
> > + ALTERNATIVE( \
> > + ANNOTATE_RETPOLINE_SAFE \
> > + "call *%[thunk_target]\n", \
> > " jmp 904f;\n" \
> > " .align 16\n" \
> > "901: call 903f;\n" \
>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Applied, thanks guys!

Ingo

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