[coreboot-gerrit] Change in coreboot[master]: soc/amd/picasso/bootblock: Clear BSS

[Raul Rangel (Code Review)]

Raul Rangel has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/42208 )

Change subject: soc/amd/picasso/bootblock: Clear BSS
......................................................................

soc/amd/picasso/bootblock: Clear BSS

The PSP does not currently reload bootblock on S3 resume. This means the
memory retains the previous values from the run. We need to clear bss to
avoid sharing state from the last run.

BUG=b:147042464
TEST=Verified staic variables are 0 on S3 resume.

Signed-off-by: Raul E Rangel 
Change-Id: I6071600b14e9edb7b09510b595e9380ae8957d9f
---
M src/soc/amd/picasso/bootblock/pre_c.S
1 file changed, 9 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/08/42208/1

diff --git a/src/soc/amd/picasso/bootblock/pre_c.S b/src/soc/amd/picasso/bootblock/pre_c.S
index 5c186f1..da9ecb9 100644
--- a/src/soc/amd/picasso/bootblock/pre_c.S
+++ b/src/soc/amd/picasso/bootblock/pre_c.S
@@ -18,6 +18,15 @@
    and	$0xfffffff0, %esp
    sub	$8, %esp

+	/* clear .bss section since it is not cleared on S3 resume. */
+	cld
+	xor	%eax, %eax
+	movl	$(_ebss), %ecx
+	movl	$(_bss), %edi
+	sub	%edi, %ecx
+	shrl	$2, %ecx
+	rep	stosl
+
    movd	%mm2, %eax
    pushl	%eax		/* tsc[63:32] */
    movd	%mm1, %eax