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Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection

From Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection
Date 2017-05-09 04:00 +0200
Message-ID <tF2Br-3r8-13@gated-at.bofh.it> (permalink)
References <tEWFH-87A-1@gated-at.bofh.it> <tEWFH-87A-13@gated-at.bofh.it> <tEZNf-1D3-1@gated-at.bofh.it> <tF0pX-25o-3@gated-at.bofh.it>
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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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[PATCH v3 0/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-05-08 21:40 +0200
  [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-05-08 21:40 +0200
    Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 01:00 +0200
      Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-05-09 01:40 +0200
        Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 04:00 +0200
          Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 19:10 +0200
            Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-05-09 19:40 +0200
              Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 19:50 +0200
  [PATCH v3 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook <keescook@chromium.org> - 2017-05-08 21:40 +0200

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