[x264-devel] [PATCH 3/6] checkasm: arm: preserve the stack alignment in x264_checkasm_checked_call

[Janne Grunau]

On 2016-11-14 23:54:50 +0200, Martin Storsjö wrote:
> From: Janne Grunau <janne-x264 at jannau.net>
> 
> The stack used by x264_checkasm_checked_call_neon was a multiple of 4
> when the checked function is called. AAPCS requires a double word (8 byte)
> aligned stack public interfaces. Since both calls are public interfaces
> the stack is misaligned when the checked is called.
> 
> This can cause issues if code called within this (which includes
> the C implementations) relies on the stack alignment.
> ---
>  tools/checkasm-arm.S | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/checkasm-arm.S b/tools/checkasm-arm.S
> index 57b4079..8242a58 100644
> --- a/tools/checkasm-arm.S
> +++ b/tools/checkasm-arm.S
> @@ -47,6 +47,9 @@ error_message:
>  
>  #define ARG_STACK 4*(MAX_ARGS - 2)
>  
> +@ align the used stack space to 8 to preserve the stack alignment
> +#define ARG_STACK_A (((ARG_STACK + pushed + 7) & ~7) - pushed)
> +
>  .macro clobbercheck variant
>  .equ pushed, 4*10
>  function x264_checkasm_call_\variant
> @@ -64,10 +67,10 @@ function x264_checkasm_call_\variant
>  
>      push        {r1}
>  
> -    sub         sp,  sp,  #ARG_STACK
> +    sub         sp,  sp,  #ARG_STACK_A
>  .equ pos, 0
>  .rept MAX_ARGS-2
> -    ldr         r12, [sp, #ARG_STACK + pushed + 8 + pos]
> +    ldr         r12, [sp, #ARG_STACK_A + pushed + 8 + pos]
>      str         r12, [sp, #pos]
>  .equ pos, pos + 4
>  .endr
> @@ -75,9 +78,9 @@ function x264_checkasm_call_\variant
>      mov         r12, r0
>      mov         r0,  r2
>      mov         r1,  r3
> -    ldrd        r2,  r3,  [sp, #ARG_STACK + pushed]
> +    ldrd        r2,  r3,  [sp, #ARG_STACK_A + pushed]
>      blx         r12
> -    add         sp,  sp,  #ARG_STACK
> +    add         sp,  sp,  #ARG_STACK_A
>      pop         {r2}
>  
>      push        {r0, r1}

ok, patch is based on my patch for libav's checkasm

Janne