[coreboot-gerrit] Change in coreboot[master]: cpu/x86/smm/smm_stub: Fix stack canary on x86_64

[Patrick Rudolph (Code Review)]

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/48215 )

Change subject: cpu/x86/smm/smm_stub: Fix stack canary on x86_64
......................................................................

cpu/x86/smm/smm_stub: Fix stack canary on x86_64

On x86_64 the cannary is 8 bytes in size, so write the additional 4 bytes to
make SMM handler happy.

Tested on Intel Skylake in long mode. No longer dies in SMM.

Change-Id: Id805c65717ec22f413803c21928d070602522b2c
Signed-off-by: Patrick Rudolph 
---
M src/cpu/x86/smm/smm_stub.S
1 file changed, 3 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/15/48215/1

diff --git a/src/cpu/x86/smm/smm_stub.S b/src/cpu/x86/smm/smm_stub.S
index 56e2504..45f634d 100644
--- a/src/cpu/x86/smm/smm_stub.S
+++ b/src/cpu/x86/smm/smm_stub.S
@@ -144,6 +144,9 @@
    movl	stack_size, %eax
    subl	%eax, %ebx /* %ebx(stack_top) - size = %ebx(stack_bottom) */
    movl	%ebx, (%ebx)
+#if ENV_X86_64
+	movl	$0, 4(%ebx)
+#endif

/* Create stack frame by pushing a NULL stack base pointer */
    pushl	$0x0