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Date: Wed, 31 May 2017 16:03:18 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
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Subject: Re: [PATCH v5 2/3] x86/asm: Add suffix macro for GEN_*_RMWcc()
Message-ID: <20170531140318.5piqb4ksynq4evwi@hirez.programming.kicks-ass.net>
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On Wed, May 31, 2017 at 06:17:16AM -0700, Kees Cook wrote:
> On Wed, May 31, 2017 at 4:13 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, May 30, 2017 at 02:39:51PM -0700, Kees Cook wrote:
> >> The coming x86 refcount protection needs to be able to add trailing
> >> instructions to the GEN_*_RMWcc() operations. This extracts the
> >> difference between the goto/non-goto cases so the helper macros
> >> can be defined outside the #ifdef cases. Additionally adds argument
> >> naming to the resulting asm for referencing from suffixed
> >> instructions, and adds clobbers for "cc", and "cx" to let suffixes
> >> use _ASM_CX, and retain any set flags.
> >
> > Another option is to simply require __GCC_ASM_FLAG_OUTPUT__ for the fast
> > refcount stuff. That would result in simpler and more readable code.
> 
> What versions of GCC support that?

IIRC 6+