Change in coreboot[master]: soc/amd/common/vboot: Verify location of CBMEMC transfer buffer

[Raul Rangel (Code Review)]

Raul Rangel has submitted this change. ( https://review.coreboot.org/c/coreboot/+/62501 )

Change subject: soc/amd/common/vboot: Verify location of CBMEMC transfer buffer
......................................................................

soc/amd/common/vboot: Verify location of CBMEMC transfer buffer

Since we want to read the non-x86 CBMEMC from SMM we need to be stricter
on where we read from. This change forces the verstage binary and x86
code to agree on the CBMEMC transfer buffer location and size.

BUG=b:221231786
TEST=Boot guybrush and verify verstage transfer buffer still ends up in
cbmem

Signed-off-by: Raul E Rangel 
Change-Id: Ida7d50bef46f280be0db1e1f185b46abb0ae5c8f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62501
Tested-by: build bot (Jenkins) 
Reviewed-by: Karthik Ramasubramanian 
---
M src/soc/amd/common/vboot/transfer_buffer.c
1 file changed, 9 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Karthik Ramasubramanian: Looks good to me, approved

diff --git a/src/soc/amd/common/vboot/transfer_buffer.c b/src/soc/amd/common/vboot/transfer_buffer.c
index 63b4f8e..e08847e 100644
--- a/src/soc/amd/common/vboot/transfer_buffer.c
+++ b/src/soc/amd/common/vboot/transfer_buffer.c
@@ -10,6 +10,8 @@
 #include <timestamp.h>
 #include <2struct.h>

+DECLARE_REGION(cbmemc_transfer)
+
 int transfer_buffer_valid(const struct transfer_info_struct *ptr)
 {
    if (ptr->magic_val == TRANSFER_MAGIC_VAL && ptr->struct_bytes == sizeof(*ptr))
@@ -85,6 +87,13 @@

cbmemc = (void *)((uintptr_t)info + info->console_offset);

+	/* Verify the cbmemc transfer buffer is where we expect it to be. */
+	if ((void *)_cbmemc_transfer != (void *)cbmemc)
+		return;
+
+	if (REGION_SIZE(cbmemc_transfer) != cbmemc_size)
+		return;
+
    /* We need to manually initialize cbmemc so we can fill the new buffer. cbmemc_init()
     * will also be called later in console_hw_init(), but it will be a no-op. */
    cbmemc_init();