On Tue, Oct 13, 2020 at 4:49 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Oct 13, 2020 at 3:32 AM Florian Weimer <fweimer@redhat.com> wrote:
> >
> > * H. J. Lu via Libc-alpha:
> >
> > > GCC 11 supports -march=x86-64-v[234] to enable x86 micro-architecture ISA
> > > levels:
> > >
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97250
> > >
> > > Binutils has been updated to support GNU_PROPERTY_X86_ISA_1_V[234] marker:
> > >
> > > https://gitlab.com/x86-psABIs/x86-64-ABI/-/merge_requests/13
> > >
> > > with
> > >
> > > commit 32930e4edbc06bc6f10c435dbcc63131715df678
> > > Author: H.J. Lu <hjl.tools@gmail.com>
> > > Date:   Fri Oct 9 05:05:57 2020 -0700
> > >
> > >     x86: Support GNU_PROPERTY_X86_ISA_1_V[234] marker
> > >
> > > in x86 ELF binaries to indicate the micro-architecture ISA level required
> > > to execute the binary.
> >
> > I'm not sure if this is the right design.  But maybe it helps to get
> > vendors to stop releasing new v2-only CPUs. 8-/
> >
> > > Add GNU_PROPERTY_X86_ISA_1_V[234] marker support to ld.so if binutils
> > > 2.32 or newer is used to build glibc:
> > >
> > > 1. Add GNU_PROPERTY_X86_ISA_1_V[234] markers to elf.h.
> > > 2. Add GNU_PROPERTY_X86_ISA_1_V[234] marker to abi-note.o based on the
> > > ISA level used to compile abi-note.o, assuming that the same ISA level
> > > is used to compile the whole glibc.
> > > 3. Add isa_1 to cpu_features to record the supported x86 ISA level.
> > > 4. Rename _dl_process_cet_property_note to _dl_process_property_note and
> > > add GNU_PROPERTY_X86_ISA_1_V[234] marker detection.
> > > 5. Update _rtld_main_check and _dl_open_check to check loaded objects
> > > with the incompatible ISA level.
> > > 6. Add a testcase to verify that dlopen an x86-64-v4 shared object fails
> > > on lesser platforms.
> >
> > It's not clear based on this description if the expectation is that the
> > search for alternative implementations continues after an attempt to
> > load an object fails due to an architecture level mismatch.
> >
>
> 1. ldconfig should issue an error for shared objects with mismatched ISA
> level and mark such shared objects in ld.so cache.
> 2. ld.so should skip shared objects with incompatible ISA level similar to
> EM_386 shared objects.   If ld.so detects it after loading such a shared
> object, ld.so should issue a hard error.
>

Here is the updated patch to properly handle both
GNU_PROPERTY_X86_FEATURE_1_AND and
GNU_PROPERTY_X86_ISA_1_NEEDED.

-- 
H.J.