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[v3,5/7] pc-bios/s390-ccw: Provide space for initial stack frame in start.S

Message ID 20230629104821.194859-6-thuth@redhat.com
State New
Headers show
Series pc-bios/s390-ccw: Fixes and improvements for start.S (and other files) | expand

Commit Message

Thomas Huth June 29, 2023, 10:48 a.m. UTC 
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>
Message-Id: <20230627074703.99608-3-thuth@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 pc-bios/s390-ccw/start.S | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
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Patch

diff --git a/pc-bios/s390-ccw/start.S b/pc-bios/s390-ccw/start.S
index d29de09cc6..abd6fe6639 100644
--- a/pc-bios/s390-ccw/start.S
+++ b/pc-bios/s390-ccw/start.S
@@ -10,10 +10,13 @@ 
  * directory.
  */
 
+#define STACK_SIZE        0x8000
+#define STACK_FRAME_SIZE  160
+
     .globl _start
 _start:
 
-    larl    %r15,stack + 0x8000     /* Set up stack */
+    larl    %r15,stack + STACK_SIZE - STACK_FRAME_SIZE   /* Set up stack */
 
     /* clear bss */
     larl    %r2,__bss_start