ec/system76: Support lockdown based on EC security state

Change-Id: I00701aa1397c24efe6f2d163822968b528f5b915

src/ec/system76/ec/Kconfig

@@ -18,6 +18,11 @@ config EC_SYSTEM76_EC_DGPU
 	bool
 	default n
 
+config EC_SYSTEM76_EC_LOCKDOWN
+	depends on EC_SYSTEM76_EC
+	bool
+	default n
+
 config EC_SYSTEM76_EC_OLED
 	depends on EC_SYSTEM76_EC
 	bool

src/ec/system76/ec/Makefile.inc

@@ -2,6 +2,7 @@
 ifeq ($(CONFIG_EC_SYSTEM76_EC),y)
 
 all-y += system76_ec.c
+ramstage-$(CONFIG_EC_SYSTEM76_EC_LOCKDOWN) += lockdown.c
 smm-$(CONFIG_DEBUG_SMI) += system76_ec.c
 
 endif

src/ec/system76/ec/lockdown.c

@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <bootstate.h>
+#include <commonlib/region.h>
+#include <fmap.h>
+#include <spi_flash.h>
+
+#include "system76_ec.h"
+
+static int protect_region_by_name(const char *name)
+{
+	int res;
+	struct region region;
+
+	res = fmap_locate_area(name, &region);
+	if (res < 0) {
+		printk(BIOS_ERR, "fmap_locate_area '%s' failed: %d\n", name, res);
+		return res;
+	}
+
+	res = spi_flash_ctrlr_protect_region(
+		boot_device_spi_flash(),
+		&region,
+		WRITE_PROTECT
+	);
+	if (res < 0) {
+		printk(BIOS_ERR, "spi_flash_ctrlr_protect_region '%s' failed: %d\n", name, res);
+		return res;
+	}
+
+	printk(BIOS_INFO, "protected '%s'\n", name);
+	return 0;
+}
+
+static void lock(void *unused)
+{
+	uint8_t state = SYSTEM76_EC_SECURITY_STATE_UNLOCK;
+	if (system76_ec_security_get(&state) < 0) {
+		printk(BIOS_INFO, "failed to get security state, assuming unlocked\n");
+		state = SYSTEM76_EC_SECURITY_STATE_UNLOCK;
+	}
+
+	printk(BIOS_INFO, "security state: %d\n", state);
+	if (state != SYSTEM76_EC_SECURITY_STATE_UNLOCK) {
+		// Protect WP_RO region, which should contain FMAP and COREBOOT
+		protect_region_by_name("WP_RO");
+		// Protect RW_MRC_CACHE region, this must be done after it is written
+		protect_region_by_name("RW_MRC_CACHE");
+		//TODO: protect entire flash except when in SMM?
+	}
+}
+
+/*
+ * Keep in sync with mrc_cache.c
+ */
+
+#if CONFIG(MRC_WRITE_NV_LATE)
+BOOT_STATE_INIT_ENTRY(BS_OS_RESUME_CHECK, BS_ON_EXIT, lock, NULL);
+#else
+BOOT_STATE_INIT_ENTRY(BS_DEV_RESOURCES, BS_ON_ENTRY, lock, NULL);
+#endif

src/ec/system76/ec/system76_ec.c

@@ -3,6 +3,7 @@
 #include <arch/io.h>
 #include <console/system76_ec.h>
 #include <timer.h>
+#include "system76_ec.h"
 
 // This is the command region for System76 EC firmware. It must be
 // enabled for LPC in the mainboard.
@@ -11,15 +12,22 @@
 
 #define REG_CMD 0
 #define REG_RESULT 1
+#define REG_DATA 2
 
 // When command register is 0, command is complete
 #define CMD_FINISHED 0
 
 // Print command. Registers are unique for each command
 #define CMD_PRINT 4
-#define CMD_PRINT_REG_FLAGS 2
+#define CMD_PRINT_REG_FLAGS REG_DATA
-#define CMD_PRINT_REG_LEN 3
+#define CMD_PRINT_REG_LEN (REG_DATA + 1)
-#define CMD_PRINT_REG_DATA 4
+#define CMD_PRINT_REG_DATA (REG_DATA + 2)
+
+// Get security state command
+#define CMD_SECURITY_GET 20
+
+// OK result, any other values are errors
+#define RESULT_OK 0
 
 static inline uint8_t system76_ec_read(uint8_t addr)
 {
@@ -59,3 +67,81 @@ void system76_ec_print(uint8_t byte)
 	if (byte == '\n' || len >= (SYSTEM76_EC_SIZE - CMD_PRINT_REG_DATA))
 		system76_ec_flush();
 }
+
+// Issue a command not checking if the console needs to be flushed
+// Do not print from this command to avoid EC protocol issues
+static int system76_ec_unsafe(uint8_t cmd, uint8_t * data, int length) {
+	// Error if length is too long
+	if (length > (SYSTEM76_EC_SIZE - REG_DATA)) {
+		return -1;
+	}
+
+	// Error if command is in progress
+	if (system76_ec_read(REG_CMD) != CMD_FINISHED) {
+		return -1;
+	}
+
+	// Write command data
+	for (int i = 0; i < length; i++) {
+		system76_ec_write(REG_DATA + i, data[i]);
+	}
+
+	// Start command
+	system76_ec_write(REG_CMD, cmd);
+
+	// Wait for command completion, for up to 10 milliseconds, with a
+	// test period of 1 microsecond
+	wait_us(10000, system76_ec_read(REG_CMD) == CMD_FINISHED);
+
+	// Error if command did not complete
+	if (system76_ec_read(REG_CMD) != CMD_FINISHED) {
+		return -1;
+	}
+
+	// Read command data
+	for (int i = 0; i < length; i++) {
+		data[i] = system76_ec_read(REG_DATA + i);
+	}
+
+	// Check result
+	if (system76_ec_read(REG_RESULT) != RESULT_OK) {
+		return -1;
+	}
+
+	return 0;
+}
+
+// Wrapper to allow issuing commands while console is being used
+// Do not print from this command to avoid EC protocol issues
+static int system76_ec_command(uint8_t cmd, uint8_t * data, int length) {
+	// Error if command is in progress
+	if (system76_ec_read(REG_CMD) != CMD_FINISHED) {
+		return -1;
+	}
+
+	// Flush print buffer if it has data
+	// Checked for completion by system76_ec_unsafe
+	if (system76_ec_read(CMD_PRINT_REG_LEN) > 0) {
+		system76_ec_flush();
+	}
+
+	// Run command now that print buffer is flushed
+	int res = system76_ec_unsafe(cmd, data, length);
+	if (res < 0) {
+		return res;
+	}
+
+	// Clear command data (for future prints)
+	// Length is checked by system76_ec_unsafe
+	for (int i = 0; i < length; i++) {
+		system76_ec_write(REG_DATA + i, 0);
+	}
+
+	return 0;
+}
+
+// Get security state
+int system76_ec_security_get(uint8_t * state) {
+	*state = 0;
+	return system76_ec_command(CMD_SECURITY_GET, state, sizeof(uint8_t));
+}

src/ec/system76/ec/system76_ec.h

@@ -0,0 +1,16 @@
+#ifndef EC_SYSTEM76_EC_H
+#define EC_SYSTEM76_EC_H
+
+// Default value, flashing is prevented, cannot be set with CMD_SECURITY_SET
+#define SYSTEM76_EC_SECURITY_STATE_LOCK 0
+// Flashing is allowed, cannot be set with CMD_SECURITY_SET
+#define SYSTEM76_EC_SECURITY_STATE_UNLOCK 1
+// Flashing will be prevented on the next reboot
+#define SYSTEM76_EC_SECURITY_STATE_PREPARE_LOCK 2
+// Flashing will be allowed on the next reboot
+#define SYSTEM76_EC_SECURITY_STATE_PREPARE_UNLOCK 3
+
+// Get security state
+int system76_ec_security_get(uint8_t * state);
+
+#endif /* EC_SYSTEM76_EC_H */