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

[Gavin Shan]

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.

Thanks,
Gavin