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

[Thomas Huth]

On 27/06/2023 11.14, Philippe Mathieu-Daudé wrote:
> On 27/6/23 10:26, Marc Hartmayer wrote:
> > 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(-)
>
>
> > > +#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.
>
> Yes please :) No need to respin.

Ok, I'll add:

diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -10,12 +10,13 @@
  * directory.
  */
 
-#define STACK_SIZE 0x8000
+#define STACK_SIZE        0x8000
+#define STACK_FRAME_SIZE  160
 
     .globl _start
 _start:
 
-    larl    %r15,stack + STACK_SIZE - 160   /* Set up stack */
+    larl    %r15,stack + STACK_SIZE - STACK_FRAME_SIZE   /* Set up stack */
 
     /* clear bss */
     larl    %r2,.bss

Thanks,
 Thomas