Merge patch series "bootstd: Add Android support"

Mattijs Korpershoek <mkorpershoek@baylibre.com> says:

Android boot flow is a bit different than a regular Linux distro.
Android relies on multiple partitions in order to boot.

A typical boot flow would be:
1. Parse the Bootloader Control Block (BCB, misc partition)
2. If BCB requested bootonce-bootloader, start fastboot and wait.
3. If BCB requested recovery or normal android, run the following:
   a. Get slot (A/B) from BCB
   b. Run AVB (Android Verified Boot) on boot partitions
   c. Load boot and vendor_boot partitions
   d. Load device-tree, ramdisk and boot

The AOSP documentation has more details at [1], [2], [3]

This has been implemented via complex boot scripts such as [4].
However, these boot script are neither very maintainable nor generic.
Moreover, DISTRO_DEFAULTS is being deprecated [5].

Add a generic Android bootflow implementation for bootstd.

For this initial version, only boot image v4 is supported.

This has been tested on sandbox using:
$ ./test/py/test.py --bd sandbox --build -k test_ut

This has also been tested on the AM62X SK EVM using TI's Android SDK[6]
To test on TI board, the following (WIP) patch is needed as well:
https://gitlab.baylibre.com/baylibre/ti/ti-u-boot/-/commit/84cceb912bccd7cdd7f9dd69bca0e5d987a1fd04

[1] https://source.android.com/docs/core/architecture/bootloader
[2] https://source.android.com/docs/core/architecture/partitions
[3] https://source.android.com/docs/core/architecture/partitions/generic-boot
[4] https://source.denx.de/u-boot/u-boot/-/blob/master/include/configs/meson64_android.h
[5] https://lore.kernel.org/r/all/20230914165615.1058529-17-sjg@chromium.org/
[6] https://software-dl.ti.com/processor-sdk-android/esd/AM62X/09_02_00/docs/android/Overview.html

16 files changed, 818 insertions, 5 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 2c6de3a1d84..19ca57d200b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -939,6 +939,13 @@ F:	include/bootstd.h
 F:	net/eth_bootdevice.c
 F:	test/boot/
 
+BOOTMETH_ANDROID
+M:	Mattijs Korpershoek <mkorpershoek@baylibre.com>
+S:	Maintained
+T:	git https://source.denx.de/u-boot/custodians/u-boot-dfu.git
+F:	boot/bootmeth_android.c
+F:	boot/bootmeth_android.h
+
 BTRFS
 M:	Marek Behún <kabel@kernel.org>
 R:	Qu Wenruo <wqu@suse.com>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index a012f5c4c9b..5fb5eac862e 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -43,6 +43,7 @@
 		mmc4 = "/mmc4";
 		mmc5 = "/mmc5";
 		mmc6 = "/mmc6";
+		mmc7 = "/mmc7";
 		pci0 = &pci0;
 		pci1 = &pci1;
 		pci2 = &pci2;
@@ -1129,6 +1130,13 @@
 		filename = "mmc6.img";
 	};
 
+	/* This is used for Android tests */
+	mmc7 {
+		status = "disabled";
+		compatible = "sandbox,mmc";
+		filename = "mmc7.img";
+	};
+
 	pch {
 		compatible = "sandbox,pch";
 	};
diff --git a/boot/Kconfig b/boot/Kconfig
index 95300b008c5..def483a41f1 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -494,6 +494,23 @@ config BOOTMETH_GLOBAL
 	  EFI bootmgr, since they take full control over which bootdevs are
 	  selected to boot.
 
+config BOOTMETH_ANDROID
+	bool "Bootdev support for Android"
+	depends on X86 || ARM || SANDBOX
+	depends on CMDLINE
+	select ANDROID_AB
+	select ANDROID_BOOT_IMAGE
+	select CMD_BCB
+	select CMD_FASTBOOT
+	select PARTITION_TYPE_GUID
+	select PARTITION_UUIDS
+	help
+	  Enables support for booting Android using bootstd. Android requires
+	  multiple partitions (misc, boot, vbmeta, ...) in storage for booting.
+
+	  Note that only MMC bootdevs are supported at present. This is caused
+	  by AVB being limited to MMC devices only.
+
 config BOOTMETH_CROS
 	bool "Bootdev support for Chromium OS"
 	depends on X86 || ARM || SANDBOX
diff --git a/boot/Makefile b/boot/Makefile
index 84ccfeaecec..75d1cd46fab 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -66,3 +66,5 @@ obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_REQUEST) += vbe_request.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE) += vbe_simple.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_FW) += vbe_simple_fw.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_OS) += vbe_simple_os.o
+
+obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_ANDROID) += bootmeth_android.o
diff --git a/boot/bootflow.c b/boot/bootflow.c
index 9aa3179c388..59d77d2385f 100644
--- a/boot/bootflow.c
+++ b/boot/bootflow.c
@@ -575,6 +575,18 @@ int bootflow_iter_check_blk(const struct bootflow_iter *iter)
 	return -ENOTSUPP;
 }
 
+int bootflow_iter_check_mmc(const struct bootflow_iter *iter)
+{
+	const struct udevice *media = dev_get_parent(iter->dev);
+	enum uclass_id id = device_get_uclass_id(media);
+
+	log_debug("uclass %d: %s\n", id, uclass_get_name(id));
+	if (id == UCLASS_MMC)
+		return 0;
+
+	return -ENOTSUPP;
+}
+
 int bootflow_iter_check_sf(const struct bootflow_iter *iter)
 {
 	const struct udevice *media = dev_get_parent(iter->dev);
diff --git a/boot/bootmeth_android.c b/boot/bootmeth_android.c
new file mode 100644
index 00000000000..6e8d3e615db
--- /dev/null
+++ b/boot/bootmeth_android.c
@@ -0,0 +1,553 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Bootmeth for Android
+ *
+ * Copyright (C) 2024 BayLibre, SAS
+ * Written by Mattijs Korpershoek <mkorpershoek@baylibre.com>
+ */
+#define LOG_CATEGORY UCLASS_BOOTSTD
+
+#include <android_ab.h>
+#include <android_image.h>
+#if CONFIG_IS_ENABLED(AVB_VERIFY)
+#include <avb_verify.h>
+#endif
+#include <bcb.h>
+#include <blk.h>
+#include <bootflow.h>
+#include <bootm.h>
+#include <bootmeth.h>
+#include <dm.h>
+#include <image.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <part.h>
+#include "bootmeth_android.h"
+
+#define BCB_FIELD_COMMAND_SZ 32
+#define BCB_PART_NAME "misc"
+#define BOOT_PART_NAME "boot"
+#define VENDOR_BOOT_PART_NAME "vendor_boot"
+
+/**
+ * struct android_priv - Private data
+ *
+ * This is read from the disk and recorded for use when the full Android
+ * kernel must be loaded and booted
+ *
+ * @boot_mode: Requested boot mode (normal, recovery, bootloader)
+ * @slot: Nul-terminated partition slot suffix read from BCB ("a\0" or "b\0")
+ * @header_version: Android boot image header version
+ */
+struct android_priv {
+	enum android_boot_mode boot_mode;
+	char slot[2];
+	u32 header_version;
+};
+
+static int android_check(struct udevice *dev, struct bootflow_iter *iter)
+{
+	/* This only works on mmc devices */
+	if (bootflow_iter_check_mmc(iter))
+		return log_msg_ret("mmc", -ENOTSUPP);
+
+	/*
+	 * This only works on whole devices, as multiple
+	 * partitions are needed to boot Android
+	 */
+	if (iter->part != 0)
+		return log_msg_ret("mmc part", -ENOTSUPP);
+
+	return 0;
+}
+
+static int scan_boot_part(struct udevice *blk, struct android_priv *priv)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(blk);
+	struct disk_partition partition;
+	char partname[PART_NAME_LEN];
+	ulong num_blks, bufsz;
+	char *buf;
+	int ret;
+
+	sprintf(partname, BOOT_PART_NAME "_%s", priv->slot);
+	ret = part_get_info_by_name(desc, partname, &partition);
+	if (ret < 0)
+		return log_msg_ret("part info", ret);
+
+	num_blks = DIV_ROUND_UP(sizeof(struct andr_boot_img_hdr_v0), desc->blksz);
+	bufsz = num_blks * desc->blksz;
+	buf = malloc(bufsz);
+	if (!buf)
+		return log_msg_ret("buf", -ENOMEM);
+
+	ret = blk_read(blk, partition.start, num_blks, buf);
+	if (ret != num_blks) {
+		free(buf);
+		return log_msg_ret("part read", -EIO);
+	}
+
+	if (!is_android_boot_image_header(buf)) {
+		free(buf);
+		return log_msg_ret("header", -ENOENT);
+	}
+
+	priv->header_version = ((struct andr_boot_img_hdr_v0 *)buf)->header_version;
+	free(buf);
+
+	return 0;
+}
+
+static int scan_vendor_boot_part(struct udevice *blk, struct android_priv *priv)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(blk);
+	struct disk_partition partition;
+	char partname[PART_NAME_LEN];
+	ulong num_blks, bufsz;
+	char *buf;
+	int ret;
+
+	sprintf(partname, VENDOR_BOOT_PART_NAME "_%s", priv->slot);
+	ret = part_get_info_by_name(desc, partname, &partition);
+	if (ret < 0)
+		return log_msg_ret("part info", ret);
+
+	num_blks = DIV_ROUND_UP(sizeof(struct andr_vnd_boot_img_hdr), desc->blksz);
+	bufsz = num_blks * desc->blksz;
+	buf = malloc(bufsz);
+	if (!buf)
+		return log_msg_ret("buf", -ENOMEM);
+
+	ret = blk_read(blk, partition.start, num_blks, buf);
+	if (ret != num_blks) {
+		free(buf);
+		return log_msg_ret("part read", -EIO);
+	}
+
+	if (!is_android_vendor_boot_image_header(buf)) {
+		free(buf);
+		return log_msg_ret("header", -ENOENT);
+	}
+	free(buf);
+
+	return 0;
+}
+
+static int android_read_slot_from_bcb(struct bootflow *bflow, bool decrement)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	struct android_priv *priv = bflow->bootmeth_priv;
+	struct disk_partition misc;
+	char slot_suffix[3];
+	int ret;
+
+	ret = part_get_info_by_name(desc, BCB_PART_NAME, &misc);
+	if (ret < 0)
+		return log_msg_ret("part", ret);
+
+	ret = ab_select_slot(desc, &misc, decrement);
+	if (ret < 0)
+		return log_msg_ret("slot", ret);
+
+	priv->slot[0] = BOOT_SLOT_NAME(ret);
+	priv->slot[1] = '\0';
+
+	sprintf(slot_suffix, "_%s", priv->slot);
+	ret = bootflow_cmdline_set_arg(bflow, "androidboot.slot_suffix",
+				       slot_suffix, false);
+	if (ret < 0)
+		return log_msg_ret("cmdl", ret);
+
+	return 0;
+}
+
+static int configure_serialno(struct bootflow *bflow)
+{
+	char *serialno = env_get("serial#");
+
+	if (!serialno)
+		return log_msg_ret("serial", -ENOENT);
+
+	return bootflow_cmdline_set_arg(bflow, "androidboot.serialno", serialno, false);
+}
+
+static int android_read_bootflow(struct udevice *dev, struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	struct disk_partition misc;
+	struct android_priv *priv;
+	char command[BCB_FIELD_COMMAND_SZ];
+	int ret;
+
+	bflow->state = BOOTFLOWST_MEDIA;
+
+	/*
+	 * bcb_find_partition_and_load() will print errors to stdout
+	 * if BCB_PART_NAME is not found. To avoid that, check if the
+	 * partition exists first.
+	 */
+	ret = part_get_info_by_name(desc, BCB_PART_NAME, &misc);
+	if (ret < 0)
+		return log_msg_ret("part", ret);
+
+	ret = bcb_find_partition_and_load("mmc", desc->devnum, BCB_PART_NAME);
+	if (ret < 0)
+		return log_msg_ret("bcb load", ret);
+
+	ret = bcb_get(BCB_FIELD_COMMAND, command, sizeof(command));
+	if (ret < 0)
+		return log_msg_ret("bcb read", ret);
+
+	priv = malloc(sizeof(struct android_priv));
+	if (!priv)
+		return log_msg_ret("buf", -ENOMEM);
+
+	if (!strcmp("bootonce-bootloader", command)) {
+		priv->boot_mode = ANDROID_BOOT_MODE_BOOTLOADER;
+		bflow->os_name = strdup("Android (bootloader)");
+	} else if (!strcmp("boot-fastboot", command)) {
+		priv->boot_mode = ANDROID_BOOT_MODE_RECOVERY;
+		bflow->os_name = strdup("Android (fastbootd)");
+	} else if (!strcmp("boot-recovery", command)) {
+		priv->boot_mode = ANDROID_BOOT_MODE_RECOVERY;
+		bflow->os_name = strdup("Android (recovery)");
+	} else {
+		priv->boot_mode = ANDROID_BOOT_MODE_NORMAL;
+		bflow->os_name = strdup("Android");
+	}
+	if (!bflow->os_name)
+		return log_msg_ret("os", -ENOMEM);
+
+	if (priv->boot_mode == ANDROID_BOOT_MODE_BOOTLOADER) {
+		/* Clear BCB */
+		memset(command, 0, sizeof(command));
+		ret = bcb_set(BCB_FIELD_COMMAND, command);
+		if (ret < 0) {
+			free(priv);
+			return log_msg_ret("bcb set", ret);
+		}
+		ret = bcb_store();
+		if (ret < 0) {
+			free(priv);
+			return log_msg_ret("bcb store", ret);
+		}
+
+		bflow->bootmeth_priv = priv;
+		bflow->state = BOOTFLOWST_READY;
+		return 0;
+	}
+
+	bflow->bootmeth_priv = priv;
+
+	/* For recovery and normal boot, we need to scan the partitions */
+	ret = android_read_slot_from_bcb(bflow, false);
+	if (ret < 0) {
+		log_err("read slot: %d", ret);
+		goto free_priv;
+	}
+
+	ret = scan_boot_part(bflow->blk, priv);
+	if (ret < 0) {
+		log_debug("scan boot failed: err=%d\n", ret);
+		goto free_priv;
+	}
+
+	if (priv->header_version != 4) {
+		log_debug("only boot.img v4 is supported %u\n", priv->header_version);
+		ret = -EINVAL;
+		goto free_priv;
+	}
+
+	ret = scan_vendor_boot_part(bflow->blk, priv);
+	if (ret < 0) {
+		log_debug("scan vendor_boot failed: err=%d\n", ret);
+		goto free_priv;
+	}
+
+	/* Ignoring return code: setting serial number is not mandatory for booting */
+	configure_serialno(bflow);
+
+	if (priv->boot_mode == ANDROID_BOOT_MODE_NORMAL) {
+		ret = bootflow_cmdline_set_arg(bflow, "androidboot.force_normal_boot",
+					       "1", false);
+		if (ret < 0) {
+			log_debug("normal_boot %d", ret);
+			goto free_priv;
+		}
+	}
+
+	bflow->state = BOOTFLOWST_READY;
+
+	return 0;
+
+ free_priv:
+	free(priv);
+	bflow->bootmeth_priv = NULL;
+	return ret;
+}
+
+static int android_read_file(struct udevice *dev, struct bootflow *bflow,
+			     const char *file_path, ulong addr, ulong *sizep)
+{
+	/*
+	 * Reading individual files is not supported since we only
+	 * operate on whole mmc devices (because we require multiple partitions)
+	 */
+	return log_msg_ret("Unsupported", -ENOSYS);
+}
+
+/**
+ * read_slotted_partition() - Read a partition by appending a slot suffix
+ *
+ * Most modern Android devices use Seamless Updates, where each partition
+ * is duplicated. For example, the boot partition has boot_a and boot_b.
+ * For more information, see:
+ * https://source.android.com/docs/core/ota/ab
+ * https://source.android.com/docs/core/ota/ab/ab_implement
+ *
+ * @blk: Block device to read
+ * @name: Partition name to read
+ * @slot: Nul-terminated slot suffixed to partition name ("a\0" or "b\0")
+ * @addr: Address where the partition content is loaded into
+ * Return: 0 if OK, negative errno on failure.
+ */
+static int read_slotted_partition(struct blk_desc *desc, const char *const name,
+				  const char slot[2], ulong addr)
+{
+	struct disk_partition partition;
+	char partname[PART_NAME_LEN];
+	int ret;
+	u32 n;
+
+	/* Ensure name fits in partname it should be: <name>_<slot>\0 */
+	if (strlen(name) > (PART_NAME_LEN - 2 - 1))
+		return log_msg_ret("name too long", -EINVAL);
+
+	sprintf(partname, "%s_%s", name, slot);
+	ret = part_get_info_by_name(desc, partname, &partition);
+	if (ret < 0)
+		return log_msg_ret("part", ret);
+
+	n = blk_dread(desc, partition.start, partition.size, map_sysmem(addr, 0));
+	if (n < partition.size)
+		return log_msg_ret("part read", -EIO);
+
+	return 0;
+}
+
+#if CONFIG_IS_ENABLED(AVB_VERIFY)
+static int avb_append_commandline_arg(struct bootflow *bflow, char *arg)
+{
+	char *key = strsep(&arg, "=");
+	char *value = arg;
+	int ret;
+
+	ret = bootflow_cmdline_set_arg(bflow, key, value, false);
+	if (ret < 0)
+		return log_msg_ret("avb cmdline", ret);
+
+	return 0;
+}
+
+static int avb_append_commandline(struct bootflow *bflow, char *cmdline)
+{
+	char *arg = strsep(&cmdline, " ");
+	int ret;
+
+	while (arg) {
+		ret = avb_append_commandline_arg(bflow, arg);
+		if (ret < 0)
+			return ret;
+
+		arg = strsep(&cmdline, " ");
+	}
+
+	return 0;
+}
+
+static int run_avb_verification(struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	struct android_priv *priv = bflow->bootmeth_priv;
+	const char * const requested_partitions[] = {"boot", "vendor_boot"};
+	struct AvbOps *avb_ops;
+	AvbSlotVerifyResult result;
+	AvbSlotVerifyData *out_data;
+	enum avb_boot_state boot_state;
+	char *extra_args;
+	char slot_suffix[3];
+	bool unlocked = false;
+	int ret;
+
+	avb_ops = avb_ops_alloc(desc->devnum);
+	if (!avb_ops)
+		return log_msg_ret("avb ops", -ENOMEM);
+
+	sprintf(slot_suffix, "_%s", priv->slot);
+
+	ret = avb_ops->read_is_device_unlocked(avb_ops, &unlocked);
+	if (ret != AVB_IO_RESULT_OK)
+		return log_msg_ret("avb lock", -EIO);
+
+	result = avb_slot_verify(avb_ops,
+				 requested_partitions,
+				 slot_suffix,
+				 unlocked,
+				 AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE,
+				 &out_data);
+
+	if (result != AVB_SLOT_VERIFY_RESULT_OK) {
+		printf("Verification failed, reason: %s\n",
+		       str_avb_slot_error(result));
+		avb_slot_verify_data_free(out_data);
+		return log_msg_ret("avb verify", -EIO);
+	}
+
+	if (unlocked)
+		boot_state = AVB_ORANGE;
+	else
+		boot_state = AVB_GREEN;
+
+	extra_args = avb_set_state(avb_ops, boot_state);
+	if (extra_args) {
+		/* extra_args will be modified after this. This is fine */
+		ret = avb_append_commandline_arg(bflow, extra_args);
+		if (ret < 0)
+			goto free_out_data;
+	}
+
+	ret = avb_append_commandline(bflow, out_data->cmdline);
+	if (ret < 0)
+		goto free_out_data;
+
+	return 0;
+
+ free_out_data:
+	if (out_data)
+		avb_slot_verify_data_free(out_data);
+
+	return log_msg_ret("avb cmdline", ret);
+}
+#else
+static int run_avb_verification(struct bootflow *bflow)
+{
+	int ret;
+
+	/* When AVB is unsupported, pass ORANGE state  */
+	ret = bootflow_cmdline_set_arg(bflow,
+				       "androidboot.verifiedbootstate",
+				       "orange", false);
+	if (ret < 0)
+		return log_msg_ret("avb cmdline", ret);
+
+	return 0;
+}
+#endif /* AVB_VERIFY */
+
+static int boot_android_normal(struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	struct android_priv *priv = bflow->bootmeth_priv;
+	int ret;
+	ulong loadaddr = env_get_hex("loadaddr", 0);
+	ulong vloadaddr = env_get_hex("vendor_boot_comp_addr_r", 0);
+
+	ret = run_avb_verification(bflow);
+	if (ret < 0)
+		return log_msg_ret("avb", ret);
+
+	/* Read slot once more to decrement counter from BCB */
+	ret = android_read_slot_from_bcb(bflow, true);
+	if (ret < 0)
+		return log_msg_ret("read slot", ret);
+
+	ret = read_slotted_partition(desc, "boot", priv->slot, loadaddr);
+	if (ret < 0)
+		return log_msg_ret("read boot", ret);
+
+	ret = read_slotted_partition(desc, "vendor_boot", priv->slot, vloadaddr);
+	if (ret < 0)
+		return log_msg_ret("read vendor_boot", ret);
+
+	set_abootimg_addr(loadaddr);
+	set_avendor_bootimg_addr(vloadaddr);
+
+	ret = bootm_boot_start(loadaddr, bflow->cmdline);
+
+	return log_msg_ret("boot", ret);
+}
+
+static int boot_android_recovery(struct bootflow *bflow)
+{
+	int ret;
+
+	ret = boot_android_normal(bflow);
+
+	return log_msg_ret("boot", ret);
+}
+
+static int boot_android_bootloader(struct bootflow *bflow)
+{
+	int ret;
+
+	ret = run_command("fastboot usb 0", 0);
+	do_reset(NULL, 0, 0, NULL);
+
+	return log_msg_ret("boot", ret);
+}
+
+static int android_boot(struct udevice *dev, struct bootflow *bflow)
+{
+	struct android_priv *priv = bflow->bootmeth_priv;
+	int ret;
+
+	switch (priv->boot_mode) {
+	case ANDROID_BOOT_MODE_NORMAL:
+		ret = boot_android_normal(bflow);
+		break;
+	case ANDROID_BOOT_MODE_RECOVERY:
+		ret = boot_android_recovery(bflow);
+		break;
+	case ANDROID_BOOT_MODE_BOOTLOADER:
+		ret = boot_android_bootloader(bflow);
+		break;
+	default:
+		printf("ANDROID: Unknown boot mode %d. Running fastboot...\n",
+		       priv->boot_mode);
+		boot_android_bootloader(bflow);
+		/* Tell we failed to boot since boot mode is unknown */
+		ret = -EFAULT;
+	}
+
+	return ret;
+}
+
+static int android_bootmeth_bind(struct udevice *dev)
+{
+	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);
+
+	plat->desc = "Android boot";
+	plat->flags = BOOTMETHF_ANY_PART;
+
+	return 0;
+}
+
+static struct bootmeth_ops android_bootmeth_ops = {
+	.check		= android_check,
+	.read_bootflow	= android_read_bootflow,
+	.read_file	= android_read_file,
+	.boot		= android_boot,
+};
+
+static const struct udevice_id android_bootmeth_ids[] = {
+	{ .compatible = "u-boot,android" },
+	{ }
+};
+
+U_BOOT_DRIVER(bootmeth_android) = {
+	.name		= "bootmeth_android",
+	.id		= UCLASS_BOOTMETH,
+	.of_match	= android_bootmeth_ids,
+	.ops		= &android_bootmeth_ops,
+	.bind		= android_bootmeth_bind,
+};
diff --git a/boot/bootmeth_android.h b/boot/bootmeth_android.h
new file mode 100644
index 00000000000..a57fad9f011
--- /dev/null
+++ b/boot/bootmeth_android.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Bootmethod for Android
+ *
+ * Copyright (C) 2024 BayLibre, SAS
+ * Written by Mattijs Korpershoek <mkorpershoek@baylibre.com>
+ */
+
+enum android_boot_mode {
+	ANDROID_BOOT_MODE_NORMAL = 0,
+
+	/*
+	 * Android "recovery" is a special boot mode that uses another ramdisk.
+	 * It can be used to "factory reset" a board or to flash logical partitions
+	 * It operates in 2 modes: adb or fastbootd
+	 * To enter recovery from Android, we can do:
+	 * $ adb reboot recovery
+	 * $ adb reboot fastboot
+	 */
+	ANDROID_BOOT_MODE_RECOVERY,
+
+	/*
+	 * Android "bootloader" is for accessing/reflashing physical partitions
+	 * Typically, this will launch a fastboot process in U-Boot.
+	 * To enter "bootloader" from Android, we can do:
+	 * $ adb reboot bootloader
+	 */
+	ANDROID_BOOT_MODE_BOOTLOADER,
+};
diff --git a/boot/image-android.c b/boot/image-android.c
index ee626972c11..09c7a44e058 100644
--- a/boot/image-android.c
+++ b/boot/image-android.c
@@ -56,6 +56,11 @@ static ulong add_trailer(ulong bootconfig_start_addr, ulong bootconfig_size)
 	return BOOTCONFIG_TRAILER_SIZE;
 }
 
+__weak ulong get_avendor_bootimg_addr(void)
+{
+	return -1;
+}
+
 static void android_boot_image_v3_v4_parse_hdr(const struct andr_boot_img_hdr_v3 *hdr,
 					       struct andr_image_data *data)
 {
diff --git a/boot/image-fdt.c b/boot/image-fdt.c
index 56dd7687f51..8332792b8e8 100644
--- a/boot/image-fdt.c
+++ b/boot/image-fdt.c
@@ -502,7 +502,7 @@ int boot_get_fdt(void *buf, const char *select, uint arch,
 		 * Firstly check if this android boot image has dtb field.
 		 */
 		dtb_idx = (u32)env_get_ulong("adtb_idx", 10, 0);
-		if (android_image_get_dtb_by_index((ulong)hdr, 0,
+		if (android_image_get_dtb_by_index((ulong)hdr, get_avendor_bootimg_addr(),
 						   dtb_idx, &fdt_addr, &fdt_size)) {
 			fdt_blob = (char *)map_sysmem(fdt_addr, 0);
 			if (fdt_check_header(fdt_blob))
diff --git a/cmd/abootimg.c b/cmd/abootimg.c
index 327712a536c..ae7a1a7c83b 100644
--- a/cmd/abootimg.c
+++ b/cmd/abootimg.c
@@ -22,6 +22,11 @@ ulong get_abootimg_addr(void)
 	return (_abootimg_addr == -1 ? image_load_addr : _abootimg_addr);
 }
 
+void set_abootimg_addr(ulong addr)
+{
+	_abootimg_addr = addr;
+}
+
 ulong get_ainit_bootimg_addr(void)
 {
 	return _ainit_bootimg_addr;
@@ -32,6 +37,11 @@ ulong get_avendor_bootimg_addr(void)
 	return _avendor_bootimg_addr;
 }
 
+void set_avendor_bootimg_addr(ulong addr)
+{
+	_avendor_bootimg_addr = addr;
+}
+
 static int abootimg_get_ver(int argc, char *const argv[])
 {
 	const struct andr_boot_img_hdr_v0 *hdr;
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index e2db66d4a25..dc5fcdbd1c9 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -15,6 +15,7 @@ CONFIG_FIT=y
 CONFIG_FIT_RSASSA_PSS=y
 CONFIG_FIT_CIPHER=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_BOOTMETH_ANDROID=y
 CONFIG_LEGACY_IMAGE_FORMAT=y
 CONFIG_MEASURED_BOOT=y
 CONFIG_BOOTSTAGE=y
@@ -40,7 +41,6 @@ CONFIG_LOG_MAX_LEVEL=9
 CONFIG_LOG_DEFAULT_LEVEL=6
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_STACKPROTECTOR=y
-CONFIG_ANDROID_AB=y
 CONFIG_CMD_CPU=y
 CONFIG_CMD_LICENSE=y
 CONFIG_CMD_SMBIOS=y
diff --git a/doc/develop/bootstd.rst b/doc/develop/bootstd.rst
index 34631089ae0..bdda90fae3f 100644
--- a/doc/develop/bootstd.rst
+++ b/doc/develop/bootstd.rst
@@ -95,6 +95,7 @@ bootflows.
 
 Note: it is possible to have a bootmeth that uses a partition or a whole device
 directly, but it is more common to use a filesystem.
+For example, the Android bootmeth uses a whole device.
 
 Note that some bootmeths are 'global', meaning that they select the bootdev
 themselves. Examples include VBE and EFI boot manager. In this case, they
@@ -277,6 +278,9 @@ script_offset_f
 script_size_f
     Size of the script to load, e.g. 0x2000
 
+vendor_boot_comp_addr_r
+    Address to which to load the vendor_boot Android image, e.g. 0xe0000000
+
 Some variables are set by script bootmeth:
 
 devtype
@@ -418,6 +422,7 @@ Bootmeth drivers are provided for:
    - EFI boot using bootefi from disk
    - VBE
    - EFI boot using boot manager
+   - Android bootflow (boot image v4)
 
 
 Command interface
@@ -786,6 +791,7 @@ To do
 Some things that need to be done to completely replace the distro-boot scripts:
 
 - implement extensions (devicetree overlays with add-on boards)
+- implement legacy (boot image v2) android boot flow
 
 Other ideas:
 
diff --git a/include/bootflow.h b/include/bootflow.h
index 6affc5e1a4f..4d2fc7b69b5 100644
--- a/include/bootflow.h
+++ b/include/bootflow.h
@@ -409,6 +409,15 @@ void bootflow_remove(struct bootflow *bflow);
 int bootflow_iter_check_blk(const struct bootflow_iter *iter);
 
 /**
+ * bootflow_iter_check_mmc() - Check that a bootflow uses a MMC device
+ *
+ * This checks the bootdev in the bootflow to make sure it uses a mmc device
+ *
+ * Return: 0 if OK, -ENOTSUPP if some other device is used (e.g. ethernet)
+ */
+int bootflow_iter_check_mmc(const struct bootflow_iter *iter);
+
+/**
  * bootflow_iter_check_sf() - Check that a bootflow uses SPI FLASH
  *
  * This checks the bootdev in the bootflow to make sure it uses SPI flash
diff --git a/include/image.h b/include/image.h
index 9daaee15cdb..dd4042d1bd9 100644
--- a/include/image.h
+++ b/include/image.h
@@ -1972,6 +1972,13 @@ bool is_android_vendor_boot_image_header(const void *vendor_boot_img);
 ulong get_abootimg_addr(void);
 
 /**
+ * set_abootimg_addr() - Set Android boot image address
+ *
+ * Return: no returned results
+ */
+void set_abootimg_addr(ulong addr);
+
+/**
  * get_ainit_bootimg_addr() - Get Android init boot image address
  *
  * Return: Android init boot image address
@@ -1986,6 +1993,13 @@ ulong get_ainit_bootimg_addr(void);
 ulong get_avendor_bootimg_addr(void);
 
 /**
+ * set_abootimg_addr() - Set Android vendor boot image address
+ *
+ * Return: no returned results
+ */
+void set_avendor_bootimg_addr(ulong addr);
+
+/**
  * board_fit_config_name_match() - Check for a matching board name
  *
  * This is used when SPL loads a FIT containing multiple device tree files
diff --git a/test/boot/bootflow.c b/test/boot/bootflow.c
index 4511cfa7f9b..8b46256fa48 100644
--- a/test/boot/bootflow.c
+++ b/test/boot/bootflow.c
@@ -27,6 +27,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+extern U_BOOT_DRIVER(bootmeth_android);
 extern U_BOOT_DRIVER(bootmeth_cros);
 extern U_BOOT_DRIVER(bootmeth_2script);
 
@@ -518,12 +519,12 @@ BOOTSTD_TEST(bootflow_cmd_boot, UT_TESTF_DM | UT_TESTF_SCAN_FDT);
  * @uts: Unit test state
  * @mmc_dev: MMC device to use, e.g. "mmc4". Note that this must remain valid
  *	in the caller until
- * @bind_cros: true to bind the ChromiumOS bootmeth
+ * @bind_cros: true to bind the ChromiumOS and Android bootmeths
  * @old_orderp: Returns the original bootdev order, which must be restored
  * Returns 0 on success, -ve on failure
  */
 static int prep_mmc_bootdev(struct unit_test_state *uts, const char *mmc_dev,
-			    bool bind_cros, const char ***old_orderp)
+			    bool bind_cros_android, const char ***old_orderp)
 {
 	static const char *order[] = {"mmc2", "mmc1", NULL, NULL};
 	struct udevice *dev, *bootstd;
@@ -545,12 +546,19 @@ static int prep_mmc_bootdev(struct unit_test_state *uts, const char *mmc_dev,
 				"bootmeth_script", 0, ofnode_null(), &dev));
 
 	/* Enable the cros bootmeth if needed */
-	if (IS_ENABLED(CONFIG_BOOTMETH_CROS) && bind_cros) {
+	if (IS_ENABLED(CONFIG_BOOTMETH_CROS) && bind_cros_android) {
 		ut_assertok(uclass_first_device_err(UCLASS_BOOTSTD, &bootstd));
 		ut_assertok(device_bind(bootstd, DM_DRIVER_REF(bootmeth_cros),
 					"cros", 0, ofnode_null(), &dev));
 	}
 
+	/* Enable the android bootmeths if needed */
+	if (IS_ENABLED(CONFIG_BOOTMETH_ANDROID) && bind_cros_android) {
+		ut_assertok(uclass_first_device_err(UCLASS_BOOTSTD, &bootstd));
+		ut_assertok(device_bind(bootstd, DM_DRIVER_REF(bootmeth_android),
+					"android", 0, ofnode_null(), &dev));
+	}
+
 	/* Change the order to include the device */
 	std = dev_get_priv(bootstd);
 	old_order = std->bootdev_order;
@@ -590,6 +598,37 @@ static int scan_mmc_bootdev(struct unit_test_state *uts, const char *mmc_dev,
 }
 
 /**
+ * scan_mmc_android_bootdev() - Set up an mmc bootdev so we can access other
+ * distros. Android bootflow might print "ANDROID:*" while scanning
+ *
+ * @uts: Unit test state
+ * @mmc_dev: MMC device to use, e.g. "mmc4"
+ * Returns 0 on success, -ve on failure
+ */
+static int scan_mmc_android_bootdev(struct unit_test_state *uts, const char *mmc_dev)
+{
+	struct bootstd_priv *std;
+	struct udevice *bootstd;
+	const char **old_order;
+
+	ut_assertok(prep_mmc_bootdev(uts, mmc_dev, true, &old_order));
+
+	console_record_reset_enable();
+	ut_assertok(run_command("bootflow scan", 0));
+	/* Android bootflow might print one or two 'ANDROID:*' logs */
+	ut_check_skipline(uts);
+	ut_check_skipline(uts);
+	ut_assert_console_end();
+
+	/* Restore the order used by the device tree */
+	ut_assertok(uclass_first_device_err(UCLASS_BOOTSTD, &bootstd));
+	std = dev_get_priv(bootstd);
+	std->bootdev_order = old_order;
+
+	return 0;
+}
+
+/**
  * scan_mmc4_bootdev() - Set up the mmc4 bootdev so we can access a fake Armbian
  *
  * @uts: Unit test state
@@ -1160,3 +1199,26 @@ static int bootflow_cros(struct unit_test_state *uts)
 	return 0;
 }
 BOOTSTD_TEST(bootflow_cros, 0);
+
+/* Test Android bootmeth  */
+static int bootflow_android(struct unit_test_state *uts)
+{
+	if (!IS_ENABLED(CONFIG_BOOTMETH_ANDROID))
+		return -EAGAIN;
+
+	ut_assertok(scan_mmc_android_bootdev(uts, "mmc7"));
+	ut_assertok(run_command("bootflow list", 0));
+
+	ut_assert_nextlinen("Showing all");
+	ut_assert_nextlinen("Seq");
+	ut_assert_nextlinen("---");
+	ut_assert_nextlinen("  0  extlinux");
+	ut_assert_nextlinen("  1  android      ready   mmc          0  mmc7.bootdev.whole        ");
+	ut_assert_nextlinen("---");
+	ut_assert_skip_to_line("(2 bootflows, 2 valid)");
+
+	ut_assert_console_end();
+
+	return 0;
+}
+BOOTSTD_TEST(bootflow_android, 0);
diff --git a/test/py/tests/test_ut.py b/test/py/tests/test_ut.py
index 58205066ec8..05e15830590 100644
--- a/test/py/tests/test_ut.py
+++ b/test/py/tests/test_ut.py
@@ -11,6 +11,7 @@ import pytest
 import u_boot_utils
 # pylint: disable=E0611
 from tests import fs_helper
+from test_android import test_abootimg
 
 def mkdir_cond(dirname):
     """Create a directory if it doesn't already exist
@@ -423,6 +424,83 @@ def setup_cros_image(cons):
 
     return fname
 
+def setup_android_image(cons):
+    """Create a 20MB disk image with Android partitions"""
+    Partition = collections.namedtuple('part', 'start,size,name')
+    parts = {}
+    disk_data = None
+
+    def set_part_data(partnum, data):
+        """Set the contents of a disk partition
+
+        This updates disk_data by putting data in the right place
+
+        Args:
+            partnum (int): Partition number to set
+            data (bytes): Data for that partition
+        """
+        nonlocal disk_data
+
+        start = parts[partnum].start * sect_size
+        disk_data = disk_data[:start] + data + disk_data[start + len(data):]
+
+    mmc_dev = 7
+    fname = os.path.join(cons.config.source_dir, f'mmc{mmc_dev}.img')
+    u_boot_utils.run_and_log(cons, 'qemu-img create %s 20M' % fname)
+    u_boot_utils.run_and_log(cons, f'cgpt create {fname}')
+
+    ptr = 40
+
+    # Number of sectors in 1MB
+    sect_size = 512
+    sect_1mb = (1 << 20) // sect_size
+
+    required_parts = [
+        {'num': 1, 'label':'misc', 'size': '1M'},
+        {'num': 2, 'label':'boot_a', 'size': '4M'},
+        {'num': 3, 'label':'boot_b', 'size': '4M'},
+        {'num': 4, 'label':'vendor_boot_a', 'size': '4M'},
+        {'num': 5, 'label':'vendor_boot_b', 'size': '4M'},
+    ]
+
+    for part in required_parts:
+        size_str = part['size']
+        if 'M' in size_str:
+            size = int(size_str[:-1]) * sect_1mb
+        else:
+            size = int(size_str)
+        u_boot_utils.run_and_log(
+            cons,
+            f"cgpt add -i {part['num']} -b {ptr} -s {size} -l {part['label']} -t basicdata {fname}")
+        ptr += size
+
+    u_boot_utils.run_and_log(cons, f'cgpt boot -p {fname}')
+    out = u_boot_utils.run_and_log(cons, f'cgpt show -q {fname}')
+
+    # Create a dict (indexed by partition number) containing the above info
+    for line in out.splitlines():
+        start, size, num, name = line.split(maxsplit=3)
+        parts[int(num)] = Partition(int(start), int(size), name)
+
+    with open(fname, 'rb') as inf:
+        disk_data = inf.read()
+
+    test_abootimg.AbootimgTestDiskImage(cons, 'bootv4.img', test_abootimg.boot_img_hex)
+    boot_img = os.path.join(cons.config.result_dir, 'bootv4.img')
+    with open(boot_img, 'rb') as inf:
+        set_part_data(2, inf.read())
+
+    test_abootimg.AbootimgTestDiskImage(cons, 'vendor_boot.img', test_abootimg.vboot_img_hex)
+    vendor_boot_img = os.path.join(cons.config.result_dir, 'vendor_boot.img')
+    with open(vendor_boot_img, 'rb') as inf:
+        set_part_data(4, inf.read())
+
+    with open(fname, 'wb') as outf:
+        outf.write(disk_data)
+
+    print('wrote to {}'.format(fname))
+
+    return fname
 
 def setup_cedit_file(cons):
     infname = os.path.join(cons.config.source_dir,
@@ -478,6 +556,7 @@ def test_ut_dm_init_bootstd(u_boot_console):
     setup_bootmenu_image(u_boot_console)
     setup_cedit_file(u_boot_console)
     setup_cros_image(u_boot_console)
+    setup_android_image(u_boot_console)
 
     # Restart so that the new mmc1.img is picked up
     u_boot_console.restart_uboot()