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

[Sam James]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> 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.
>
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> ---
>  sysdeps/x86_64/nptl/rseq-access.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/sysdeps/x86_64/nptl/rseq-access.h b/sysdeps/x86_64/nptl/rseq-access.h
> index 535e36281f..bc966b2972 100644
> --- a/sysdeps/x86_64/nptl/rseq-access.h
> +++ b/sysdeps/x86_64/nptl/rseq-access.h
> @@ -27,18 +27,18 @@
>         asm volatile ("movb %%fs:%P2(%q3),%b0"				      \
>  		     : "=q" (__value)					      \
>  		     : "0" (0), "i" (offsetof (struct rseq_area, member)),    \
> -		       "r" (__rseq_offset));				      \
> +		       "r" ((long long int) __rseq_offset));		      \
>       else if (sizeof (__value) == 4)					      \
>         asm volatile ("movl %%fs:%P1(%q2),%0"				      \
>  		     : "=r" (__value)					      \
>  		     : "i" (offsetof (struct rseq_area, member)),	      \
> -		       "r" (__rseq_offset));				      \
> +		       "r" ((long long int) __rseq_offset));		      \
>       else /* 8 */							      \
>         {								      \
>  	 asm volatile ("movq %%fs:%P1(%q2),%q0"				      \
>  		       : "=r" (__value)					      \
>  		       : "i" (offsetof (struct rseq_area, member)),	      \
> -			 "r" (__rseq_offset));				      \
> +		         "r" ((long long int) __rseq_offset));		      \
>         }								      \
>       __value; })
>  
> @@ -56,12 +56,12 @@
>         asm volatile ("movb %b0,%%fs:%P1(%q2)" :				      \
>  		     : "iq" (value),					      \
>  		       "i" (offsetof (struct rseq_area, member)),	      \
> -		       "r" (__rseq_offset));				      \
> +		       "r" ((long long int) __rseq_offset));		      \
>       else if (sizeof (RSEQ_SELF()->member) == 4)			      \
>         asm volatile ("movl %0,%%fs:%P1(%q2)" :				      \
>  		     : IMM_MODE (value),				      \
>  		       "i" (offsetof (struct rseq_area, member)),	      \
> -		       "r" (__rseq_offset));				      \
> +		       "r" ((long long int) __rseq_offset));		      \
>       else /* 8 */							      \
>         {								      \
>  	 /* Since movq takes a signed 32-bit immediate or a register source   \
> @@ -70,7 +70,7 @@
>  	 asm volatile ("movq %q0,%%fs:%P1(%q2)" :			      \
>  		       : "er" ((uint64_t) cast_to_integer (value)),	      \
>  			 "i" (offsetof (struct rseq_area, member)),	      \
> -			 "r" (__rseq_offset));				      \
> +		         "r" ((long long int) __rseq_offset));		      \
>         }})
>  
>  /* Set member of the RSEQ area directly.  */

Thanks.