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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 01:10 +0200
Message-ID <u56gp-73P-1@gated-at.bofh.it> (permalink)
References (1 earlier) <u4KIW-PC-27@gated-at.bofh.it> <u52Zc-4Fq-15@gated-at.bofh.it> <u538S-4JC-7@gated-at.bofh.it> <u53iy-4NJ-11@gated-at.bofh.it> <u566K-6L0-11@gated-at.bofh.it>
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On Wed, Jul 19, 2017 at 03:50:14PM -0700, Kees Cook wrote:
> >> >  })
> >> > +
> >> > +#define ASM_UNREACHABLE                                                        \
> >> > +       "999: .pushsection .discard.unreachable\n\t"                    \
> >> > +       ".long 999b - .\n\t"                                            \
> >> > +       ".popsection\n\t"
> >>
> >> Just so I understand, we'll get a single byte added for each exception
> >> case, but it'll get discarded during final link?
> >
> > I think it's four bytes actually, but yeah, the section gets stripped at
> > vmlinux link time.
> 
> Right, yes.
> 
> BTW, I think this needs compiler.h coverage instead of the #else in
> compiler-gcc.h (since it's different from how annotate_unreachable is
> used only in compiler-gcc.h. I'll adjust.

Ah, right.  Sounds good.

> Also, in looking at CONFIG_STACK_VALIDATION, do you want it to just
> warn and skip, or do you want to error out the build if validation
> isn't available but it's in the .config?

I think the current warn and skip behavior is fine.  It's usually not a
life-or-death matter, and if it is, you'll be checking the warnings
anyway.

-- 
Josh

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Thread

[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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