vboot: Introduce alternate boot functionality

Introduce alternate boot functionality both via keyboard shortcut
("Ctrl+L") to directly boot into the default alternate bootloader,
and via menu ("Alternate bootloader" on dev screen) to show a screen
listing available bootloaders.

BUG=b:146399181, b:161092974
TEST=make clean && make runtests
BRANCH=puff, zork

Cq-Depend: chromium:2339040
Signed-off-by: Joel Kitching <kitching@google.com>
Change-Id: I28f157936017719dc95656db147967f5e61a1407
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2335017
Commit-Queue: Yu-Ping Wu <yupingso@chromium.org>
Tested-by: Hsuan Ting Chen <roccochen@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-by: Joel Kitching <kitching@chromium.org>

4 files changed, 133 insertions, 0 deletions

diff --git a/firmware/2lib/2ui.c b/firmware/2lib/2ui.c
index d80002d5..4ddbcef0 100644
--- a/firmware/2lib/2ui.c
+++ b/firmware/2lib/2ui.c
@@ -410,6 +410,8 @@ vb2_error_t developer_action(struct vb2_ui_context *ui)
 	if (ui->key == VB_KEY_CTRL('D') ||
 	    (DETACHABLE && ui->key == VB_BUTTON_VOL_DOWN_LONG_PRESS))
 		return vb2_ui_developer_mode_boot_internal_action(ui);
+	if (ui->key == VB_KEY_CTRL('L'))
+		return vb2_ui_developer_mode_boot_alternate_action(ui);
 	if (ui->key == '\t')
 		return vb2_ui_screen_change(ui, VB2_SCREEN_DEBUG_INFO);
 
diff --git a/firmware/2lib/2ui_screens.c b/firmware/2lib/2ui_screens.c
index 2e5dbfaf..e1b02d0a 100644
--- a/firmware/2lib/2ui_screens.c
+++ b/firmware/2lib/2ui_screens.c
@@ -642,6 +642,7 @@ static const struct vb2_screen_info recovery_disk_step3_screen = {
 #define DEVELOPER_MODE_ITEM_RETURN_TO_SECURE 1
 #define DEVELOPER_MODE_ITEM_BOOT_INTERNAL 2
 #define DEVELOPER_MODE_ITEM_BOOT_EXTERNAL 3
+#define DEVELOPER_MODE_ITEM_SELECT_BOOTLOADER 4
 
 vb2_error_t developer_mode_init(struct vb2_ui_context *ui)
 {
@@ -662,11 +663,20 @@ vb2_error_t developer_mode_init(struct vb2_ui_context *ui)
 		ui->state->disabled_item_mask |=
 			1 << DEVELOPER_MODE_ITEM_BOOT_EXTERNAL;
 
+	/* Don't show "Select alternate bootloader" button if not allowed. */
+	if (!vb2_dev_boot_legacy_allowed(ui->ctx))
+		ui->state->disabled_item_mask |=
+			1 << DEVELOPER_MODE_ITEM_SELECT_BOOTLOADER;
+
 	/* Choose the default selection. */
 	switch (default_boot) {
 	case VB2_DEV_DEFAULT_BOOT_TARGET_EXTERNAL:
 		ui->state->selected_item = DEVELOPER_MODE_ITEM_BOOT_EXTERNAL;
 		break;
+	case VB2_DEV_DEFAULT_BOOT_TARGET_LEGACY:
+		ui->state->selected_item =
+			DEVELOPER_MODE_ITEM_SELECT_BOOTLOADER;
+		break;
 	default:
 		ui->state->selected_item = DEVELOPER_MODE_ITEM_BOOT_INTERNAL;
 		break;
@@ -781,6 +791,10 @@ static const struct vb2_menu_item developer_mode_items[] = {
 		.text = "Boot from external disk",
 		.action = vb2_ui_developer_mode_boot_external_action,
 	},
+	[DEVELOPER_MODE_ITEM_SELECT_BOOTLOADER] = {
+		.text = "Select alternate bootloader",
+		.target = VB2_SCREEN_DEVELOPER_SELECT_BOOTLOADER,
+	},
 	ADVANCED_OPTIONS_ITEM,
 	POWER_OFF_ITEM,
 };
@@ -860,6 +874,108 @@ static const struct vb2_screen_info developer_invalid_disk_screen = {
 };
 
 /******************************************************************************/
+/* VB2_SCREEN_DEVELOPER_SELECT_BOOTLOADER */
+
+const struct vb2_menu_item developer_select_bootloader_items_before[] = {
+	LANGUAGE_SELECT_ITEM,
+};
+
+const struct vb2_menu_item developer_select_bootloader_items_after[] = {
+	BACK_ITEM,
+	POWER_OFF_ITEM,
+};
+
+vb2_error_t vb2_ui_developer_mode_boot_alternate_action(
+	struct vb2_ui_context *ui)
+{
+	uint32_t altfw_num;
+	const size_t menu_before_len =
+		ARRAY_SIZE(developer_select_bootloader_items_before);
+
+	if (!(ui->ctx->flags & VB2_CONTEXT_DEVELOPER_MODE) ||
+	    !vb2_dev_boot_allowed(ui->ctx) ||
+	    !vb2_dev_boot_legacy_allowed(ui->ctx)) {
+		VB2_DEBUG("ERROR: Dev mode alternate bootloader not allowed\n");
+		ui->error_beep = 1;
+		return VB2_REQUEST_UI_CONTINUE;
+	}
+
+	if (vb2ex_get_bootloader_count() == 0) {
+		VB2_DEBUG("ERROR: No bootloader was found\n");
+		ui->error_beep = 1;
+		return VB2_REQUEST_UI_CONTINUE;
+	}
+
+	if (ui->key == VB_KEY_CTRL('L')) {
+		altfw_num = 0;
+		VB2_DEBUG("Try booting from default bootloader\n");
+	} else {
+		altfw_num = ui->state->selected_item - menu_before_len + 1;
+		VB2_DEBUG("Try booting from bootloader #%u\n", altfw_num);
+	}
+
+	/* VbExLegacy will not return if successful */
+	VbExLegacy(altfw_num);
+
+	VB2_DEBUG("ERROR: Alternate bootloader failed\n");
+	/* TODO(b/161092974): Leverage the error dialog on error. */
+	ui->error_beep = 1;
+	return VB2_REQUEST_UI_CONTINUE;
+}
+
+static const struct vb2_menu *get_bootloader_menu(struct vb2_ui_context *ui)
+{
+	int i;
+	uint32_t num_bootloaders, num_items;
+	struct vb2_menu_item *items;
+	const size_t menu_before_len =
+		ARRAY_SIZE(developer_select_bootloader_items_before);
+	const size_t menu_after_len =
+		ARRAY_SIZE(developer_select_bootloader_items_after);
+
+	if (ui->bootloader_menu.num_items > 0)
+		return &ui->bootloader_menu;
+
+	/* TODO(b/161092974): Show error dialog if no bootloader. */
+	num_bootloaders = vb2ex_get_bootloader_count();
+	VB2_DEBUG("num_bootloaders: %u\n", num_bootloaders);
+	num_items = num_bootloaders + menu_before_len + menu_after_len;
+	items = malloc(num_items * sizeof(struct vb2_menu_item));
+	if (!items) {
+		VB2_DEBUG("ERROR: malloc failed for bootloader items\n");
+		return NULL;
+	}
+
+	/* Copy prefix items to the begin. */
+	memcpy(&items[0],
+	       developer_select_bootloader_items_before,
+	       menu_before_len * sizeof(struct vb2_menu_item));
+
+	/* Copy bootloaders. */
+	for (i = 0; i < num_bootloaders; i++) {
+		items[i + menu_before_len].text = "Some bootloader";
+		items[i + menu_before_len].action =
+			vb2_ui_developer_mode_boot_alternate_action;
+	}
+
+	/* Copy postfix items to the end. */
+	memcpy(&items[num_items - menu_after_len],
+	       developer_select_bootloader_items_after,
+	       menu_after_len * sizeof(struct vb2_menu_item));
+
+	ui->bootloader_menu.num_items = num_items;
+	ui->bootloader_menu.items = items;
+
+	return &ui->bootloader_menu;
+}
+
+static const struct vb2_screen_info developer_select_bootloader_screen = {
+	.id = VB2_SCREEN_DEVELOPER_SELECT_BOOTLOADER,
+	.name = "Select alternate bootloader",
+	.get_menu = get_bootloader_menu,
+};
+
+/******************************************************************************/
 /* VB2_SCREEN_DIAGNOSTICS */
 
 static const struct vb2_menu_item diagnostics_items[] = {
@@ -1071,6 +1187,7 @@ static const struct vb2_screen_info *screens[] = {
 	&developer_to_norm_screen,
 	&developer_boot_external_screen,
 	&developer_invalid_disk_screen,
+	&developer_select_bootloader_screen,
 	&diagnostics_screen,
 	&diagnostics_storage_screen,
 	&diagnostics_memory_quick_screen,
diff --git a/firmware/2lib/include/2api.h b/firmware/2lib/include/2api.h
index ee3bb53e..56c0b80c 100644
--- a/firmware/2lib/include/2api.h
+++ b/firmware/2lib/include/2api.h
@@ -1316,6 +1316,8 @@ enum vb2_screen {
 	VB2_SCREEN_DEVELOPER_BOOT_EXTERNAL	= 0x320,
 	/* Invalid external disk inserted */
 	VB2_SCREEN_DEVELOPER_INVALID_DISK	= 0x330,
+	/* Select alternate bootloader ("legacy boot") */
+	VB2_SCREEN_DEVELOPER_SELECT_BOOTLOADER	= 0x340,
 	/* Diagnostic tools */
 	VB2_SCREEN_DIAGNOSTICS			= 0x400,
 	/* Storage diagnostic screen */
@@ -1380,6 +1382,13 @@ int vb2ex_physical_presence_pressed(void);
 uint32_t vb2ex_get_locale_count(void);
 
 /**
+ * Return the number of available alternate bootloaders.
+ *
+ * @returns Number of alternate bootloaders.  0 if none or on error.
+ */
+uint32_t vb2ex_get_bootloader_count(void);
+
+/**
  * Delay for at least the specified number of milliseconds.
  *
  * @param msec			Duration in milliseconds.
diff --git a/firmware/2lib/include/2ui.h b/firmware/2lib/include/2ui.h
index cc21f580..2fefaf32 100644
--- a/firmware/2lib/include/2ui.h
+++ b/firmware/2lib/include/2ui.h
@@ -103,6 +103,9 @@ struct vb2_ui_context {
 	/* For language selection screen. */
 	struct vb2_menu language_menu;
 
+	/* For bootloader selection screen. */
+	struct vb2_menu bootloader_menu;
+
 	/* For error beep sound. */
 	int error_beep;
 
@@ -118,6 +121,8 @@ vb2_error_t vb2_ui_developer_mode_boot_internal_action(
 	struct vb2_ui_context *ui);
 vb2_error_t vb2_ui_developer_mode_boot_external_action(
 	struct vb2_ui_context *ui);
+vb2_error_t vb2_ui_developer_mode_boot_alternate_action(
+	struct vb2_ui_context *ui);
 
 /**
  * Get info struct of a screen.