linux-kernel - Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

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Message-ID: <87o7wtnay6.fsf@oldenburg.str.redhat.com>
Date:   Tue, 09 Aug 2022 09:16:33 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Gavin Shan <gshan@...hat.com>
Cc:     kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, maz@...nel.org, oliver.upton@...ux.dev,
        andrew.jones@...ux.dev, seanjc@...gle.com,
        mathieu.desnoyers@...icios.com, yihyu@...hat.com,
        shan.gavin@...il.com
Subject: Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

* Gavin Shan:

>> __builtin_thread_pointer doesn't work on all architectures/GCC
>> versions.
>> Is this a problem for selftests?
>> 
>
> It's a problem as the test case is running on all architectures. I think I
> need introduce our own __builtin_thread_pointer() for where it's not
> supported: (1) PowerPC  (2) x86 without GCC 11
>
> Please let me know if I still have missed cases where
> __buitin_thread_pointer() isn't supported?

As far as I know, these are the two outliers that also have rseq
support.  The list is a bit longer if we also consider non-rseq
architectures (csky, hppa, ia64, m68k, microblaze, sparc, don't know
about the Linux architectures without glibc support).

Thanks,
Florian