On Wed, May 31, 2017 at 7:03 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > 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@xxxxxxxxxxxxx> 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+ Given how many folks are still using 4.9 (and lower, see the thread with Arnd[1]), I'd like to just keep this as I have it. It's not much less readable, IMO (It was already pretty complex). I cleaned it up a little before making it more ugly, so I think on sum, it's only a little more weird. I think that's better than making this compiler-specific or copy/pasting. -Kees [1] https://lkml.org/lkml/2017/4/25/66 -- Kees Cook Pixel Security
