src/security/vboot/vboot_loader.c

/*
 * This file is part of the coreboot project.
 *
 * Copyright 2015 Google, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <arch/early_variables.h>
#include <cbfs.h>
#include <console/console.h>
#include <ec/google/chromeec/ec.h>
#include <rmodule.h>
#include <string.h>
#include <security/vboot/misc.h>
#include <security/vboot/symbols.h>
#include <security/vboot/vboot_common.h>

/* Ensure vboot configuration is valid: */
_Static_assert(IS_ENABLED(CONFIG_VBOOT_STARTS_IN_BOOTBLOCK) +
	       IS_ENABLED(CONFIG_VBOOT_STARTS_IN_ROMSTAGE) == 1,
	       "vboot must either start in bootblock or romstage (not both!)");
_Static_assert(!IS_ENABLED(CONFIG_VBOOT_SEPARATE_VERSTAGE) ||
	       IS_ENABLED(CONFIG_VBOOT_STARTS_IN_BOOTBLOCK),
	       "stand-alone verstage must start in (i.e. after) bootblock");
_Static_assert(!IS_ENABLED(CONFIG_VBOOT_RETURN_FROM_VERSTAGE) ||
	       IS_ENABLED(CONFIG_VBOOT_SEPARATE_VERSTAGE),
	       "return from verstage only makes sense for separate verstages");

/* The stage loading code is compiled and entered from multiple stages. The
 * helper functions below attempt to provide more clarity on when certain
 * code should be called. */

static int verification_should_run(void)
{
	if (IS_ENABLED(CONFIG_VBOOT_SEPARATE_VERSTAGE))
		return ENV_VERSTAGE;
	else if (IS_ENABLED(CONFIG_VBOOT_STARTS_IN_ROMSTAGE))
		return ENV_ROMSTAGE;
	else if (IS_ENABLED(CONFIG_VBOOT_STARTS_IN_BOOTBLOCK))
		return ENV_BOOTBLOCK;
	else
		die("impossible!");
}

static int verstage_should_load(void)
{
	if (IS_ENABLED(CONFIG_VBOOT_SEPARATE_VERSTAGE))
		return ENV_BOOTBLOCK;
	else
		return 0;
}

static int vboot_executed CAR_GLOBAL;

int vb2_logic_executed(void)
{
	/* If we are in a stage that would load the verstage or execute the
	   vboot logic directly, we store the answer in a global. */
	if (verstage_should_load() || verification_should_run())
		return car_get_var(vboot_executed);

	if (IS_ENABLED(CONFIG_VBOOT_STARTS_IN_BOOTBLOCK)) {
		/* All other stages are "after the bootblock" */
		return !ENV_BOOTBLOCK;
	} else if (IS_ENABLED(CONFIG_VBOOT_STARTS_IN_ROMSTAGE)) {
		/* Post-RAM stages are "after the romstage" */
#ifdef __PRE_RAM__
		return 0;
#else
		return 1;
#endif
	} else {
		die("impossible!");
	}
}

static void vboot_prepare(void)
{
	if (verification_should_run()) {
		/* Note: this path is not used for VBOOT_RETURN_FROM_VERSTAGE */
		verstage_main();
		car_set_var(vboot_executed, 1);
		vb2_save_recovery_reason_vbnv();
	} else if (verstage_should_load()) {
		struct cbfsf file;
		struct prog verstage =
			PROG_INIT(PROG_VERSTAGE,
				CONFIG_CBFS_PREFIX "/verstage");

		printk(BIOS_DEBUG, "VBOOT: Loading verstage.\n");

		/* load verstage from RO */
		if (cbfs_boot_locate(&file, prog_name(&verstage), NULL))
			die("failed to load verstage");

		cbfs_file_data(prog_rdev(&verstage), &file);

		if (cbfs_prog_stage_load(&verstage))
			die("failed to load verstage");

		/* verify and select a slot */
		prog_run(&verstage);

		/* This is not actually possible to hit this condition at
		 * runtime, but this provides a hint to the compiler for dead
		 * code elimination below. */
		if (!IS_ENABLED(CONFIG_VBOOT_RETURN_FROM_VERSTAGE))
			return;

		car_set_var(vboot_executed, 1);
	}

	/*
	 * Fill in vboot cbmem objects before moving to ramstage so all
	 * downstream users have access to vboot results. This path only
	 * applies to platforms employing VBOOT_STARTS_IN_ROMSTAGE because
	 * cbmem comes online prior to vboot verification taking place. For
	 * other platforms the vboot cbmem objects are initialized when
	 * cbmem comes online.
	 */
	if (ENV_ROMSTAGE && IS_ENABLED(CONFIG_VBOOT_STARTS_IN_ROMSTAGE)) {
		vb2_store_selected_region();
		vboot_fill_handoff();
	}
}

static int vboot_locate(struct cbfs_props *props)
{
	struct region selected_region;

	/* Don't honor vboot results until the vboot logic has run. */
	if (!vb2_logic_executed())
		return -1;

	if (vb2_get_selected_region(&selected_region))
		return -1;

	props->offset = region_offset(&selected_region);
	props->size = region_sz(&selected_region);

	return 0;
}

const struct cbfs_locator vboot_locator = {
	.name = "VBOOT",
	.prepare = vboot_prepare,
	.locate = vboot_locate,
};