[PATCH v2] x86-64: Cast __rseq_offset to long long int [BZ #32543]

[Florian Weimer]

* H. J. Lu:

> commit 494d65129ed5ae1154b75cc189bbdde5e9ecf1df
> Author: Michael Jeanson <mjeanson@efficios.com>
> Date:   Thu Aug 1 10:35:34 2024 -0400
>
>     nptl: Introduce <rseq-access.h> for RSEQ_* accessors
>
> added things like
>
>        asm volatile ("movl %%fs:%P1(%q2),%0"                                  \
>                      : "=r" (__value)                                         \
>                      : "i" (offsetof (struct rseq_area, member)),             \
>                        "r" (__rseq_offset));				      \
>
> But this doesn't work for x32 when __rseq_offset is negative since the
> address is computed as
>
> FS + 32-bit to 64-bit zero extension of __rseq_offset
> + offsetof (struct rseq_area, member)
>
> Cast __rseq_offset to long long int
>
>                        "r" ((long long int) __rseq_offset));		      \
>
> to sign-extend 32-bit __rseq_offset to 64-bit.  This is a no-op for x86-64
> since x86-64 __rseq_offset is 64-bit.  This fixes BZ #32543.

Looks good to me.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Thanks,
Florian