V2 [PATCH] x86: Adjust tst-cpu-features-supports.c for GCC 11

[Florian Weimer]

* H. J. Lu:

> On Fri, Dec 4, 2020 at 12:12 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > Set RDRAND usable if CPU supports RDRAND.  Also check HAS_CPU_FEATURE
>> > instead of CPU_FEATURE_USABLE for FSGSBASE, LM and XSAVES since
>> > FSGSBASE/LM require kernel support and XSAVES is supervisor-mode only.
>>
>> I think the commit subject is misleading because the RDRAND part is a
>> glibc bug fix.  Rest looks okay to me.
>>
>
> Here is the V2 patch.  It changed IBT and SHSTK to check HAS_CPU_FEATURE
> since they need OS support.

Patch is okay.  But I do wonder why __builtin_cpu_supports doesn't
handle this.  Based on the GCC documention, I would say it should
perform what you call a “usable” check.

Thanks,
Florian
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