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SubjectRe: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection
On Mon, May 08, 2017 at 04:31:11PM -0700, Kees Cook wrote:
> On Mon, May 8, 2017 at 3:53 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > On Mon, May 08, 2017 at 12:32:52PM -0700, Kees Cook wrote:
> >> +#define REFCOUNT_EXCEPTION \
> >> + "movl $0x7fffffff, %[counter]\n\t" \
> >> + "int $"__stringify(X86_REFCOUNT_VECTOR)"\n" \
> >> + "0:\n\t" \
> >> + _ASM_EXTABLE(0b, 0b)
> >
> > Despite the objtool warnings going away, this still uses the exception
> > table in a new way, which will confuse objtool. I need to do some more
> > thinking about the best way to fix it, either as a change to your patch
> > or a change to objtool.
>
> In that it's not a "true" exception?

Right. And also that it doesn't need the "fixup" since it would return
to the same address anyway.

--
Josh

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