Re: [PATCH] elf: Update GNU_PROPERTY_X86_XXX macros [BZ #23797]

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Sun, Oct 28, 2018 at 5:11 PM Mark Wielaard <mark@klomp.org> wrote:
>
> Hi,
>
> On Wed, 2018-10-24 at 13:03 +0200, Mark Wielaard wrote:
> > Some questions about how to interpret the new constant values vs the
> > old ones. I am not sure I understand how this is fully backwards
> > compatible.
>
> Currently the elfutils code just handles GNU_PROPERTY_STACK_SIZE,
> GNU_PROPERTY_NO_COPY_ON_PROTECTED and GNU_PROPERTY_X86_FEATURE_1_AND
> with IBT and SHSTK. But none of the other types/data that would be
> renamed/renumbered with this patch.
>
> It would be really helpful if you could answer the questions below to
> better understand how this new data fits in and what the backwards
> compatibility story is.
>

x86 assembler supports

  -mx86-used-note=[no|yes] (default: yes)
                          generate x86 used ISA and feature properties

It marks x86 objects with

[hjl@gnu-4 x32]$ readelf -n /libx32/libc-2.27.so

Displaying notes found in: .note.gnu.build-id
  Owner                 Data size Description
  GNU                  0x00000014 NT_GNU_BUILD_ID (unique build ID bitstri
ng)
    Build ID: c45c0d715994e76aa2842845502c978738d02ed6

Displaying notes found in: .note.gnu.property
  Owner                 Data size Description
  GNU                  0x00000024 NT_GNU_PROPERTY_TYPE_0
      Properties: x86 feature: IBT, SHSTK
x86 ISA used: CMOV, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, AVX, AVX2, A
VX512F
x86 feature used: x86, x87, XMM, YMM, ZMM

H.J.