tss: implement tlcl_save_state

When an untrusted OS is running, we would like to use the Cr50
vendor-specific VENDOR_CC_TPM_MODE command to disable TPM.
Before doing this, we should save TPM state.  Implement
tlcl_save_state for this purpose.

This needs to live in coreboot codebase since on S3 resume path,
depthcharge is not reached.

Implement the function in both tcg-1.2 and tcg-2.0 for
completeness.

BUG=b:70681930,b:118202153
TEST=hack a call to tlcl_save_state into coreboot on S3 resume
     verify in AP console that it is called

Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: I8b51ca68456fc9b655e4dc2d0958b7c040d50510
Reviewed-on: https://review.coreboot.org/c/29646
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/security/tpm/tss/tcg-1.2/tss.c b/src/security/tpm/tss/tcg-1.2/tss.c
index 0cb7eaa819..b11d6a3d16 100644
--- a/src/security/tpm/tss/tcg-1.2/tss.c
+++ b/src/security/tpm/tss/tcg-1.2/tss.c
@@ -178,6 +178,12 @@ uint32_t tlcl_resume(void)
 	return send(tpm_resume_cmd.buffer);
 }
 
+uint32_t tlcl_save_state(void)
+{
+	VBDEBUG("TPM: Save state\n");
+	return send(tpm_savestate_cmd.buffer);
+}
+
 uint32_t tlcl_self_test_full(void)
 {
 	VBDEBUG("TPM: Self test full\n");