Re: [PATCH 2/4] hurd: Align signal stack pointer after allocating stackframe

[Samuel Thibault]

Applied, thanks!

Sergey Bugaev via Libc-alpha, le lun. 15 mai 2023 11:33:21 +0300, a ecrit:
> sizeof (*stackframe) appears to be divisible by 16, but we should not
> rely on that. So make sure to leave enough space for the stackframe
> first, and then align the final pointer at 16 bytes.
> 
> Checked on x86_64-gnu.
> 
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
>  sysdeps/mach/hurd/x86/trampoline.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/sysdeps/mach/hurd/x86/trampoline.c 
> b/sysdeps/mach/hurd/x86/trampoline.c
> index 19bddad8..1f92064e 100644
> --- a/sysdeps/mach/hurd/x86/trampoline.c
> +++ b/sysdeps/mach/hurd/x86/trampoline.c
> @@ -196,15 +196,14 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, const 
> struct sigaction *action
>  #endif
>      }
>  
> +  /* Push the arguments to call `trampoline' on the stack.  */
> +  sigsp -= sizeof (*stackframe);
>  #ifdef __x86_64__
>    /* Align SP at 16 bytes.  Coupled with the fact that sigreturn_addr is
>       16-byte aligned within the stackframe struct, this ensures that it ends
>       up on a 16-byte aligned address, as required by the ABI.  */
>    sigsp = (void *) ((uintptr_t) sigsp & ~15UL);
>  #endif
> -
> -  /* Push the arguments to call `trampoline' on the stack.  */
> -  sigsp -= sizeof (*stackframe);
>    stackframe = sigsp;
>  
>    if (_hurdsig_catch_memory_fault (stackframe))
> -- 
> 2.40.1
> 

-- 
Samuel
---
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