coreboot: check Cr50 PM mode on normal boot
Under some scenarios the key ladder on the Cr50 can get disabled. If
this state is detected, trigger a reboot of the Cr50 to restore full
TPM functionality.
BUG=b:121463033
BRANCH=none
TEST=Built coreboot on sarien and grunt platforms.
TEST=Ran 'gsctool -a -m disable' and reboot. Verified coreboot sends
VENDOR_CC_IMMEDIATE_RESET command to Cr50 and that the Cr50 resets and
then the platform boots normally.
TEST=Performed Cr50 rollback to 0.0.22 which does not support the
VENDOR_CC_TPM_MODE command, confirmed that platform boots normally and
the coreboot log captures the unsupported command.
Tested-by: Keith Short <keithshort@chromium.org>
Change-Id: I70e012efaf1079d43890e909bc6b5015bef6835a
Signed-off-by: Keith Short <keithshort@chromium.org>
Reviewed-on: https://review.coreboot.org/c/31260
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
diff --git a/src/vendorcode/google/chromeos/cr50_enable_update.c b/src/vendorcode/google/chromeos/cr50_enable_update.c
index da9a16d..660fe2e 100644
--- a/src/vendorcode/google/chromeos/cr50_enable_update.c
+++ b/src/vendorcode/google/chromeos/cr50_enable_update.c
@@ -23,7 +23,75 @@
#include <security/vboot/vboot_common.h>
#include <vendorcode/google/chromeos/chromeos.h>
-void __weak mainboard_cr50_update_reset(void) {}
+#define C50_RESET_DELAY_MS 1000
+
+void __weak mainboard_prepare_cr50_reset(void) {}
+
+/**
+ * Check if the Cr50 TPM state requires a chip reset of the Cr50 device.
+ *
+ * Returns 0 if the Cr50 TPM state is good or if the TPM_MODE command is
+ * unsupported. Returns 1 if the Cr50 was reset.
+ */
+static int cr50_reset_if_needed(uint16_t timeout_ms)
+{
+ int ret;
+ int cr50_must_reset = 0;
+ uint8_t tpm_mode;
+
+ ret = tlcl_cr50_get_tpm_mode(&tpm_mode);
+
+ if (ret == TPM_E_NO_SUCH_COMMAND) {
+ printk(BIOS_INFO,
+ "Cr50 does not support TPM mode command\n");
+ /* Older Cr50 firmware, assume no Cr50 reset is required */
+ return 0;
+ }
+
+ if (ret == TPM_E_MUST_REBOOT) {
+ /*
+ * Cr50 indicated a reboot is required to restore TPM
+ * functionality.
+ */
+ cr50_must_reset = 1;
+ } else if (ret != TPM_SUCCESS) {
+ /* TPM command failed, continue booting. */
+ printk(BIOS_ERR,
+ "ERROR: Attempt to get CR50 TPM mode failed: %x\n", ret);
+ return 0;
+ }
+
+ /* If the TPM mode is not enabled-tentative, then the TPM mode is locked
+ * and cannot be changed. Perform a Cr50 reset because vboot may need
+ * to disable TPM as part of booting an untrusted OS.
+ *
+ * This is not an expected state, as the Cr50 always sets the TPM mode
+ * to TPM_MODE_ENABLED_TENTATIVE during any TPM reset action.
+ */
+ if (tpm_mode != TPM_MODE_ENABLED_TENTATIVE) {
+ printk(BIOS_NOTICE,
+ "NOTICE: Unexpected Cr50 TPM mode (%d). "
+ "A Cr50 reset is required.\n", tpm_mode);
+ cr50_must_reset = 1;
+ }
+
+ /* If TPM state is okay, no reset needed. */
+ if (!cr50_must_reset)
+ return 0;
+
+ ret = tlcl_cr50_immediate_reset(timeout_ms);
+
+ if (ret != TPM_SUCCESS) {
+ /* TPM command failed, continue booting. */
+ printk(BIOS_ERR,
+ "ERROR: Attempt to reset CR50 failed: %x\n",
+ ret);
+ return 0;
+ }
+
+ /* Cr50 is about to be reset, caller needs to prepare */
+ return 1;
+}
static void enable_update(void *unused)
{
@@ -37,34 +105,54 @@
ret = tlcl_lib_init();
if (ret != VB2_SUCCESS) {
- printk(BIOS_ERR, "tlcl_lib_init() failed for CR50 update: %x\n",
- ret);
+ printk(BIOS_ERR,
+ "ERROR: tlcl_lib_init() failed for CR50 update: %x\n",
+ ret);
return;
}
/* Reboot in 1000 ms if necessary. */
- ret = tlcl_cr50_enable_update(1000, &num_restored_headers);
+ ret = tlcl_cr50_enable_update(C50_RESET_DELAY_MS,
+ &num_restored_headers);
if (ret != TPM_SUCCESS) {
- printk(BIOS_ERR, "Attempt to enable CR50 update failed: %x\n",
- ret);
+ printk(BIOS_ERR,
+ "ERROR: Attempt to enable CR50 update failed: %x\n",
+ ret);
return;
}
- /* If no headers were restored there is no reset forthcoming. */
- if (!num_restored_headers)
- return;
+ if (!num_restored_headers) {
+ /* If no headers were restored there is no reset forthcoming due
+ * to a Cr50 firmware update. Also check if the Cr50 TPM mode
+ * requires a reset.
+ *
+ * TODO: to eliminate a TPM command during every boot, the
+ * TURN_UPDATE_ON command could be enhanced/replaced in the Cr50
+ * firmware to perform the TPM mode/key-ladder check in addition
+ * to the FW version check.
+ */
+
+ /*
+ * If the Cr50 was not reset, continue booting.
+ */
+ if (!cr50_reset_if_needed(C50_RESET_DELAY_MS))
+ return;
+
+ printk(BIOS_INFO, "Waiting for CR50 reset to enable TPM.\n");
+ elog_add_event(ELOG_TYPE_CR50_NEED_RESET);
+ } else {
+ printk(BIOS_INFO,
+ "Waiting for CR50 reset to pick up update.\n");
+ elog_add_event(ELOG_TYPE_CR50_UPDATE);
+ }
/* Give mainboard a chance to take action */
- mainboard_cr50_update_reset();
-
- elog_add_event(ELOG_TYPE_CR50_UPDATE);
+ mainboard_prepare_cr50_reset();
/* clear current post code avoid chatty eventlog on subsequent boot*/
post_code(0);
- printk(BIOS_INFO, "Waiting for CR50 reset to pick up update.\n");
-
if (IS_ENABLED(CONFIG_POWER_OFF_ON_CR50_UPDATE))
poweroff();
halt();