Re: [PATCH v2 2/4] pc-bios/s390-ccw: Provide space for initial stack frame in start.S

[Marc Hartmayer]

Thomas Huth <thuth@redhat.com> writes:

> Providing the space of a stack frame is the duty of the caller,
> so we should reserve 160 bytes before jumping into the main function.
> Otherwise the main() function might write past the stack array.
>
> While we're at it, add a proper STACK_SIZE macro for the stack size
> instead of using magic numbers (this is also required for the following
> patch).
>
> Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> Reviewed-by: Cédric Le Goater <clg@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  pc-bios/s390-ccw/start.S | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
> index d29de09cc6..29b0a9ece0 100644
> --- a/pc-bios/s390-ccw/start.S
> +++ b/pc-bios/s390-ccw/start.S
> @@ -10,10 +10,12 @@
>   * directory.
>   */
>  
> +#define STACK_SIZE 0x8000
> +
>      .globl _start
>  _start:
>  
> -    larl    %r15,stack + 0x8000     /* Set up stack */
> +    larl    %r15,stack + STACK_SIZE - 160   /* Set up stack */
                                         ^^^
                                         You can also add a macro for this
                                         - e.g. STACK_FRAME_SIZE.

Besides that,
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>

>  
>      /* clear bss */
>      larl    %r2,__bss_start
> -- 
> 2.39.3
>
-- 
Kind regards / Beste Grüße
   Marc Hartmayer

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