Re: [PATCH 1/3] x86: Separate out x86_regset for 32 and 64 bit

[Kees Cook <keescook@chromium.org>]

On Tue, Mar 15, 2022 at 01:17:04PM -0700, Rick Edgecombe wrote:
> In ptrace, the x86_32_regsets and x86_64_regsets are constructed such that
> there are no gaps in the arrays. This appears to be for two reasons. One,
> the code in fill_thread_core_info() can't handle the gaps. This will be
> addressed in a future patch. And two, not having gaps shrinks the size of
> the array in memory.
> 
> Both regset arrays draw their indices from a shared enum x86_regset, but 32
> bit and 64 bit don't all support the same regsets. In the case of
> IA32_EMULATION they can be compiled in at the same time. So this enum has
> to be laid out in a special way such that there are no gaps for both
> x86_32_regsets and x86_64_regsets. This involves creating aliases for
> enum’s that are only in one view or the other, or creating multiple
> versions like in the case of REGSET_IOPERM32/REGSET_IOPERM64.
> 
> Simplify the construction of these arrays by just fully separating out the
> enums for 32 bit and 64 bit. Add some bitsize-free defines for
> REGSET_GENERAL and REGSET_FP since they are the only two referred to in
> bitsize generic code.
> 
> This should have no functional change and is only changing how constants
> are generated and named. The enum is local to this file, so it does not
> introduce any burden on code calling from other places in the kernel now
> having to worry about whether to use a 32 bit or 64 bit enum name.
> 
> [1] https://lore.kernel.org/lkml/20180717162502.32274-1-yu-cheng.yu@intel.com/
> 
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Have you verified there's no binary difference in machine code output?

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook