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Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection

From Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection
Date 2017-07-20 01:40 +0200
Message-ID <u56Jr-7ff-15@gated-at.bofh.it> (permalink)
References <u4KIW-PC-21@gated-at.bofh.it> <u4KIW-PC-27@gated-at.bofh.it> <u52Zc-4Fq-15@gated-at.bofh.it> <u56q6-77M-17@gated-at.bofh.it>
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On Wed, Jul 19, 2017 at 04:12:37PM -0700, Kees Cook wrote:
> On Wed, Jul 19, 2017 at 12:37 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > +#define ASM_UNREACHABLE                                                        \
> > +       "999: .pushsection .discard.unreachable\n\t"                    \
> > +       ".long 999b - .\n\t"                                            \
> > +       ".popsection\n\t"
> 
> Will this end up running into the same bug fixed with
> 3d1e236022cc1426b0834565995ddee2ca231cee and the __LINE__ macro? I
> could tell under which conditions gcc would do this kind of merging...

I hope not, but objtool should complain about it if it does.

We could involve the __LINE__ macro, or some other way to make the
labels unique, but that might complicate the code a bit, so we can delay
doing that unless necessary.

-- 
Josh

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[PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-19 02:10 +0200
  [PATCH v6 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook <keescook@chromium.org> - 2017-07-19 02:10 +0200
  [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-19 02:10 +0200
    Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-07-19 21:40 +0200
      Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-19 21:50 +0200
        Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-07-19 22:00 +0200
          Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-20 01:00 +0200
            Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-07-20 01:10 +0200
      Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-20 01:20 +0200
        Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow  protection Josh Poimboeuf <jpoimboe@redhat.com> - 2017-07-20 01:40 +0200
  Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Ingo Molnar <mingo@kernel.org> - 2017-07-20 11:20 +0200
    Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-20 19:20 +0200
      Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-21 01:00 +0200
        Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Ingo Molnar <mingo@kernel.org> - 2017-07-21 10:00 +0200
    Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Andrew Morton <akpm@linux-foundation.org> - 2017-07-21 23:30 +0200
      Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Kees Cook <keescook@chromium.org> - 2017-07-22 05:40 +0200
        Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Michael Ellerman <mpe@ellerman.id.au> - 2017-07-24 08:40 +0200
          Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Peter Zijlstra <peterz@infradead.org> - 2017-07-24 10:50 +0200
            Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Michael Ellerman <mpe@ellerman.id.au> - 2017-07-24 14:10 +0200
              Re: [PATCH v6 0/2] x86: Implement fast refcount overflow protection Peter Zijlstra <peterz@infradead.org> - 2017-07-24 14:30 +0200

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