Re: [PATCH] strub: Only unbias stack point for SPARC_STACK_BOUNDARY_HACK [PR113100]

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Jan 8, 2024 at 3:35 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi,
>
> As PR113100 shows, the unbiasing introduced by r14-6737 can
> cause the scrubbing to overrun and screw some critical data
> on stack like saved toc base consequently cause segfault on
> Power.
>
> By checking PR112917, IMHO we should keep this unbiasing
> guarded under SPARC_STACK_BOUNDARY_HACK (TARGET_ARCH64 &&
> TARGET_STACK_BIAS), similar to some existing code special
> treating SPARC stack bias.
>
> Bootstrapped and regtested on x86_64-redhat-linux and
> powerpc64{,le}-linux-gnu.  All reported failures in
> PR113100 are gone.  I also expect the culprit commit can
> affect those ports with nonzero STACK_POINTER_OFFSET.
>
> Is it ok for trunk?

OK

> BR,
> Kewen
> -----
>         PR middle-end/113100
>
> gcc/ChangeLog:
>
>         * builtins.cc (expand_builtin_stack_address): Guard stack point
>         adjustment with SPARC_STACK_BOUNDARY_HACK.
> ---
>  gcc/builtins.cc | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/builtins.cc b/gcc/builtins.cc
> index 125ea158ebf..9bad1e962b4 100644
> --- a/gcc/builtins.cc
> +++ b/gcc/builtins.cc
> @@ -5450,6 +5450,7 @@ expand_builtin_stack_address ()
>    rtx ret = convert_to_mode (ptr_mode, copy_to_reg (stack_pointer_rtx),
>                              STACK_UNSIGNED);
>
> +#ifdef SPARC_STACK_BOUNDARY_HACK
>    /* Unbias the stack pointer, bringing it to the boundary between the
>       stack area claimed by the active function calling this builtin,
>       and stack ranges that could get clobbered if it called another
> @@ -5476,7 +5477,9 @@ expand_builtin_stack_address ()
>       (caller) function's active area as well, whereas those pushed or
>       allocated temporarily for a call are regarded as part of the
>       callee's stack range, rather than the caller's.  */
> -  ret = plus_constant (ptr_mode, ret, STACK_POINTER_OFFSET);
> +  if (SPARC_STACK_BOUNDARY_HACK)
> +    ret = plus_constant (ptr_mode, ret, STACK_POINTER_OFFSET);
> +#endif
>
>    return force_reg (ptr_mode, ret);
>  }
> --
> 2.39.3