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    SubjectRe: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35
    ----- On Aug 9, 2022, at 8:21 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

    > ----- Gavin Shan <gshan@redhat.com> wrote:
    >> Hi Florian,
    >>
    >> On 8/9/22 5:16 PM, Florian Weimer wrote:
    >> >>> __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).
    >> >
    >>
    >> For kvm/selftests, there are 3 architectures involved actually. So we
    >> just need consider 4 cases: aarch64, x86, s390 and other. For other
    >> case, we just use __builtin_thread_pointer() to maintain code's
    >> integrity, but it's not called at all.
    >>
    >> I think kvm/selftest is always relying on glibc if I'm correct.
    >
    > All those are handled in the rseq selftests and in librseq. Why duplicate all
    > that logic again?

    More to the point, considering that we have all the relevant rseq registration
    code in tools/testing/selftests/rseq/rseq.c already, and the relevant thread
    pointer getter code in tools/testing/selftests/rseq/rseq-*thread-pointer.h,
    is there an easy way to get test applications in tools/testing/selftests/kvm
    and in tools/testing/selftests/rseq to share that common code ?

    Keeping duplicated compatibility code is bad for long-term maintainability.

    Thanks,

    Mathieu

    --
    Mathieu Desnoyers
    EfficiOS Inc.
    http://www.efficios.com

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