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

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Tue, 27 Jun 2023 09:47:01 +0200
Thomas Huth <thuth@redhat.com> wrote:

> 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>


with Marc's suggestion applied:

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.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 */
>  
>      /* clear bss */
>      larl    %r2,__bss_start