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

[Raul Rangel (Code Review)]

Attention is currently required from: Jason Glenesk, Marshall Dawson, Fred Reitberger, Felix Held.
Raul Rangel has uploaded this change for review. ( 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
---
M src/soc/amd/common/vboot/transfer_buffer.c
1 file changed, 9 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/01/62501/1

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();