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>

src/include/elog.h

@@ -223,6 +223,9 @@ struct elog_event_mem_cache_update {
 #define  ELOG_SLEEP_PENDING_PM1_WAKE       0x01
 #define  ELOG_SLEEP_PENDING_GPE0_WAKE      0x02
 
+/* Cr50 reset to enable TPM */
+#define ELOG_TYPE_CR50_NEED_RESET         0xb2
+
 struct elog_event_extended_event {
 	u8 event_type;
 	u32 event_complement;

src/mainboard/google/sarien/chromeos.c

@@ -115,7 +115,7 @@ int get_lid_switch(void)
 	return 1;
 }
 
-void mainboard_cr50_update_reset(void)
+void mainboard_prepare_cr50_reset(void)
 {
 #if ENV_RAMSTAGE
 	/* Ensure system powers up after CR50 reset */

src/security/tpm/tss/tcg-2.0/tss_marshaling.c

@@ -266,6 +266,14 @@ static int marshal_cr50_vendor_command(struct obuf *ob, void *command_body)
 	uint16_t *sub_command = command_body;
 
 	switch (*sub_command) {
+	case TPM2_CR50_SUB_CMD_IMMEDIATE_RESET:
+		/* The 16-bit timeout parameter is optional for the
+		 * IMMEDIATE_RESET command.  However in coreboot, the timeout
+		 * parameter must be specified.
+		 */
+		rc |= obuf_write_be16(ob, sub_command[0]);
+		rc |= obuf_write_be16(ob, sub_command[1]);
+		break;
 	case TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS:
 		rc |= obuf_write_be16(ob, *sub_command);
 		break;
@@ -276,6 +284,18 @@ static int marshal_cr50_vendor_command(struct obuf *ob, void *command_body)
 	case TPM2_CR50_SUB_CMD_GET_REC_BTN:
 		rc |= obuf_write_be16(ob, *sub_command);
 		break;
+	case TPM2_CR50_SUB_CMD_TPM_MODE:
+		/* The Cr50 TPM_MODE command supports an optional parameter.
+		 * When the parameter is present the Cr50 will attempt to change
+		 * the TPM state (enable or disable) and returns the new state
+		 * in the response.  When the parameter is absent, the Cr50
+		 * returns the current TPM state.
+		 *
+		 * coreboot currently only uses the TPM get capability and does
+		 * not set a new TPM state with the Cr50.
+		 */
+		rc |= obuf_write_be16(ob, *sub_command);
+		break;
 	default:
 		/* Unsupported subcommand. */
 		printk(BIOS_WARNING, "Unsupported cr50 subcommand: 0x%04x\n",
@@ -471,12 +491,16 @@ static int unmarshal_vendor_command(struct ibuf *ib,
 		return -1;
 
 	switch (vcr->vc_subcommand) {
+	case TPM2_CR50_SUB_CMD_IMMEDIATE_RESET:
+		break;
 	case TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS:
 		break;
 	case TPM2_CR50_SUB_CMD_TURN_UPDATE_ON:
 		return ibuf_read_be8(ib, &vcr->num_restored_headers);
 	case TPM2_CR50_SUB_CMD_GET_REC_BTN:
 		return ibuf_read_be8(ib, &vcr->recovery_button_state);
+	case TPM2_CR50_SUB_CMD_TPM_MODE:
+		return ibuf_read_be8(ib, &vcr->tpm_mode);
 	default:
 		printk(BIOS_ERR,
 		       "%s:%d - unsupported vendor command %#04x!\n",

src/security/tpm/tss/tcg-2.0/tss_structures.h

@@ -298,6 +298,7 @@ struct vendor_command_response {
 	union {
 		uint8_t num_restored_headers;
 		uint8_t recovery_button_state;
+		uint8_t tpm_mode;
 	};
 };
 

src/security/tpm/tss/vendor/cr50/cr50.c

@@ -47,7 +47,7 @@ uint32_t tlcl_cr50_enable_update(uint16_t timeout_ms,
 	response = tpm_process_command(TPM2_CR50_VENDOR_COMMAND, command_body);
 
 	if (!response || response->hdr.tpm_code)
-		return TPM_E_INTERNAL_INCONSISTENCY;
+		return TPM_E_IOERROR;
 
 	*num_restored_headers = response->vcr.num_restored_headers;
 	return TPM_SUCCESS;
@@ -63,8 +63,67 @@ uint32_t tlcl_cr50_get_recovery_button(uint8_t *recovery_button_state)
 	response = tpm_process_command(TPM2_CR50_VENDOR_COMMAND, &sub_command);
 
 	if (!response || response->hdr.tpm_code)
-		return TPM_E_INTERNAL_INCONSISTENCY;
+		return TPM_E_IOERROR;
 
 	*recovery_button_state = response->vcr.recovery_button_state;
 	return TPM_SUCCESS;
 }
+
+uint32_t tlcl_cr50_get_tpm_mode(uint8_t *tpm_mode)
+{
+	struct tpm2_response *response;
+	uint16_t mode_command = TPM2_CR50_SUB_CMD_TPM_MODE;
+	*tpm_mode = TPM_MODE_INVALID;
+
+	printk(BIOS_INFO, "Reading cr50 TPM mode\n");
+
+	response = tpm_process_command(TPM2_CR50_VENDOR_COMMAND, &mode_command);
+
+	if (!response)
+		return TPM_E_IOERROR;
+
+	if (response->hdr.tpm_code == VENDOR_RC_INTERNAL_ERROR) {
+		/*
+		 * The Cr50 returns VENDOR_RC_INTERNAL_ERROR iff the key ladder
+		 * is disabled. The Cr50 requires a reboot to re-enable the key
+		 * ladder.
+		 */
+		return TPM_E_MUST_REBOOT;
+	}
+
+	if (response->hdr.tpm_code == VENDOR_RC_NO_SUCH_COMMAND) {
+		/*
+		 * Explicitly inform caller when command is not supported
+		 */
+		return TPM_E_NO_SUCH_COMMAND;
+	}
+
+	if (response->hdr.tpm_code) {
+		/* Unexpected return code from Cr50 */
+		return TPM_E_IOERROR;
+	}
+
+	/* TPM command completed without error */
+	*tpm_mode = response->vcr.tpm_mode;
+
+	return TPM_SUCCESS;
+}
+
+uint32_t tlcl_cr50_immediate_reset(uint16_t timeout_ms)
+{
+	struct tpm2_response *response;
+	uint16_t reset_command_body[] = {
+		TPM2_CR50_SUB_CMD_IMMEDIATE_RESET, timeout_ms};
+
+	/*
+	 * Issue an immediate reset to the Cr50.
+	 */
+	printk(BIOS_INFO, "Issuing cr50 reset\n");
+	response = tpm_process_command(TPM2_CR50_VENDOR_COMMAND,
+				       &reset_command_body);
+
+	if (!response)
+		return TPM_E_IOERROR;
+
+	return TPM_SUCCESS;
+}

src/security/tpm/tss/vendor/cr50/cr50.h

@@ -23,9 +23,35 @@
    to extending generically because the marshaling code is assuming all
    knowledge of all commands. */
 #define TPM2_CR50_VENDOR_COMMAND ((TPM_CC)(TPM_CC_VENDOR_BIT_MASK | 0))
+#define TPM2_CR50_SUB_CMD_IMMEDIATE_RESET (19)
 #define TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS (21)
 #define TPM2_CR50_SUB_CMD_TURN_UPDATE_ON (24)
 #define TPM2_CR50_SUB_CMD_GET_REC_BTN (29)
+#define TPM2_CR50_SUB_CMD_TPM_MODE (40)
+
+/* Cr50 vendor-specific error codes. */
+#define VENDOR_RC_ERR              0x00000500
+enum cr50_vendor_rc {
+	VENDOR_RC_INTERNAL_ERROR = (VENDOR_RC_ERR | 6),
+	VENDOR_RC_NO_SUCH_COMMAND = (VENDOR_RC_ERR | 127),
+};
+
+enum cr50_tpm_mode {
+	/*
+	 * Default state: TPM is enabled, and may be set to either
+	 * TPM_MODE_ENABLED or TPM_MODE_DISABLED.
+	 */
+	TPM_MODE_ENABLED_TENTATIVE = 0,
+
+	/* TPM is enabled, and mode may not be changed. */
+	TPM_MODE_ENABLED = 1,
+
+	/* TPM is disabled, and mode may not be changed. */
+	TPM_MODE_DISABLED = 2,
+
+	TPM_MODE_INVALID,
+};
+
 
 /**
  * CR50 specific tpm command to enable nvmem commits before internal timeout
@@ -53,4 +79,26 @@ uint32_t tlcl_cr50_enable_update(uint16_t timeout_ms,
  */
 uint32_t tlcl_cr50_get_recovery_button(uint8_t *recovery_button_state);
 
+/**
+ * CR50 specific TPM command sequence to query the current TPM mode.
+ *
+ * Returns TPM_SUCCESS if TPM mode command completed, the Cr50 does not need a
+ * reboot, and the tpm_mode parameter is set to the current TPM mode.
+ * Returns TPM_E_MUST_REBOOT if TPM mode command completed, but the Cr50
+ * requires a reboot.
+ * Returns TPM_E_NO_SUCH_COMMAND if the Cr50 does not support the command.
+ * Other returns value indicate a failure accessing the TPM.
+ */
+uint32_t tlcl_cr50_get_tpm_mode(uint8_t *tpm_mode);
+
+/**
+ * CR50 specific TPM command sequence to trigger an immediate reset to the Cr50
+ * device after the specified timeout in milliseconds.  A timeout of zero means
+ * "IMMEDIATE REBOOT".
+ *
+ * Return value indicates success or failure of accessing the TPM.
+ */
+uint32_t tlcl_cr50_immediate_reset(uint16_t timeout_ms);
+
+
 #endif /* CR50_TSS_STRUCTURES_H_ */

src/security/tpm/tss_errors.h

@@ -42,5 +42,6 @@
 #define TPM_E_NV_DEFINED             ((uint32_t)0x0000500b)  /* vboot local */
 #define TPM_E_INVALID_ARG            ((uint32_t)0x0000500c)
 #define TPM_E_HASH_ERROR             ((uint32_t)0x0000500d)
+#define TPM_E_NO_SUCH_COMMAND        ((uint32_t)0x0000500e)
 
 #endif /* TSS_ERRORS_H_ */

src/vendorcode/google/chromeos/chromeos.h

@@ -33,8 +33,11 @@ static inline void mark_watchdog_tombstone(void) { return; }
 static inline void reboot_from_watchdog(void) { return; }
 #endif /* CONFIG_CHROMEOS */
 
-/* Defined as weak function in cr50_enable_update.c */
-void mainboard_cr50_update_reset(void);
+/**
+ * Perform any platform specific actions required prior to resetting the Cr50.
+ * Defined as weak function in cr50_enable_update.c
+ */
+void mainboard_prepare_cr50_reset(void);
 
 struct romstage_handoff;
 

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 @@ static void enable_update(void *unused)
 	ret = tlcl_lib_init();
 
 	if (ret != VB2_SUCCESS) {
-		printk(BIOS_ERR, "tlcl_lib_init() failed for CR50 update: %x\n",
+		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",
+		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)
+	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;
 
-	/* Give mainboard a chance to take action */
-	mainboard_cr50_update_reset();
-
+		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_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();