boot/bootmeth_cros.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Bootmethod for ChromiumOS
  *
  * Copyright 2023 Google LLC
  * Written by Simon Glass <sjg@chromium.org>
  */

 #define LOG_CATEGORY UCLASS_BOOTSTD

 #include <blk.h>
 #include <bootdev.h>
 #include <bootflow.h>
 #include <bootm.h>
 #include <bootmeth.h>
 #include <display_options.h>
 #include <dm.h>
 #include <efi.h>
 #include <malloc.h>
 #include <mapmem.h>
 #include <part.h>
 #include <linux/sizes.h>
 #include "bootmeth_cros.h"

 static const efi_guid_t cros_kern_type = PARTITION_CROS_KERNEL;

 /*
  * Layout of the ChromeOS kernel
  *
  * Partitions 2 and 4 contain kernels with type GUID_CROS_KERNEL
  *
  * Contents are:
  *
  * Offset	Contents
  *   0		struct vb2_keyblock
  *   m		struct vb2_kernel_preamble
  *   m + n	kernel buffer
  *
  * m is keyblock->keyblock_size
  * n is preamble->preamble_size
  *
  * The kernel buffer itself consists of various parts:
  *
  * Offset	Contents
  *   m + n	kernel image (Flat vmlinux binary or FIT)
  *   b - 8KB	Command line text
  *   b - 4KB	X86 setup block (struct boot_params, extends for about 16KB)
  *   b          X86 bootloader (continuation of setup block)
  *   b + 16KB	X86 setup block (copy, used for hold data pointed to)
  *
  * b is m + n + preamble->bootloader_address - preamble->body_load_address
  *
  * Useful metadata extends from b - 8KB through to b + 32 KB
  */

 enum {
 	PROBE_SIZE	= SZ_4K,	/* initial bytes read from partition */

 	X86_SETUP_OFFSET = -0x1000,	/* setup offset relative to base */
 	CMDLINE_OFFSET	= -0x2000,	/* cmdline offset relative to base */
 	X86_KERNEL_OFFSET = 0x4000,	/* kernel offset relative to base */
 };

 /**
  * struct cros_priv - Private data
  *
  * This is read from the disk and recorded for use when the full kernel must
  * be loaded and booted
  *
  * @body_offset: Offset of kernel body from start of partition (in bytes)
  * @body_size: Size of kernel body in bytes
  * @part_start: Block offset of selected partition from the start of the disk
  * @body_load_address: Nominal load address for kernel body
  * @bootloader_address: Address of bootloader, after body is loaded at
  *	body_load_address
  * @bootloader_size:  Size of bootloader in bytes
  * @info_buf: Buffer containing ChromiumOS info
  */
 struct cros_priv {
 	ulong body_offset;
 	ulong body_size;
 	lbaint_t part_start;
 	ulong body_load_address;
 	ulong bootloader_address;
 	ulong bootloader_size;
 	void *info_buf;
 };

 static int cros_check(struct udevice *dev, struct bootflow_iter *iter)
 {
 	/* This only works on block and network devices */
 	if (bootflow_iter_check_blk(iter))
 		return log_msg_ret("blk", -ENOTSUPP);

 	return 0;
 }

 static int copy_cmdline(const char *from, const char *uuid, char **bufp)
 {
 	const int maxlen = 2048;
 	char buf[maxlen];
 	char *cmd, *to, *end;
 	int len;

 	/* Allow space for cmdline + UUID */
 	len = strnlen(from, sizeof(buf));
 	if (len >= maxlen)
 		return -E2BIG;

 	log_debug("uuid %d %s\n", uuid ? (int)strlen(uuid) : 0, uuid);
 	for (to = buf, end = buf + maxlen - UUID_STR_LEN - 1; *from; from++) {
 		if (to >= end)
 			return -E2BIG;
 		if (from[0] == '%' && from[1] == 'U' && uuid &&
 		    strlen(uuid) == UUID_STR_LEN) {
 			strcpy(to, uuid);
 			to += UUID_STR_LEN;
 			from++;
 		} else {
 			*to++ = *from;
 		}
 	}
 	*to = '\0';
 	len = to - buf;
 	cmd = strdup(buf);
 	if (!cmd)
 		return -ENOMEM;
 	free(*bufp);
 	*bufp = cmd;

 	return 0;
 }

 /**
  * scan_part() - Scan a kernel partition to see if has a ChromeOS header
  *
  * This reads the first PROBE_SIZE of a partition, loookng for
  * VB2_KEYBLOCK_MAGIC
  *
  * @blk: Block device to scan
  * @partnum: Partition number to scan
  * @info: Please to put partition info
  * @hdrp: Return allocated keyblock header on success
  */
 static int scan_part(struct udevice *blk, int partnum,
 		     struct disk_partition *info, struct vb2_keyblock **hdrp)
 {
 	struct blk_desc *desc = dev_get_uclass_plat(blk);
 	struct vb2_keyblock *hdr;
 	efi_guid_t type;
 	ulong num_blks;
 	int ret;

 	if (!partnum)
 		return log_msg_ret("efi", -ENOENT);

 	ret = part_get_info(desc, partnum, info);
 	if (ret)
 		return log_msg_ret("part", ret);

 	/* Check for kernel partition type */
 	log_debug("part %x: type=%s\n", partnum, info->type_guid);
 	if (uuid_str_to_bin(info->type_guid, type.b, UUID_STR_FORMAT_GUID))
 		return log_msg_ret("typ", -EINVAL);

 	if (guidcmp(&cros_kern_type, &type))
 		return log_msg_ret("typ", -ENOEXEC);

 	/* Make a buffer for the header information */
 	num_blks = PROBE_SIZE >> desc->log2blksz;
 	log_debug("Reading header, blk=%s, start=%lx, blocks=%lx\n",
 		  blk->name, (ulong)info->start, num_blks);
 	hdr = memalign(SZ_1K, PROBE_SIZE);
 	if (!hdr)
 		return log_msg_ret("hdr", -ENOMEM);
 	ret = blk_read(blk, info->start, num_blks, hdr);
 	if (ret != num_blks) {
 		free(hdr);
 		return log_msg_ret("inf", -EIO);
 	}

 	if (memcmp(VB2_KEYBLOCK_MAGIC, hdr->magic, VB2_KEYBLOCK_MAGIC_SIZE)) {
 		free(hdr);
 		log_debug("no magic\n");
 		return -ENOENT;
 	}

 	*hdrp = hdr;

 	return 0;
 }

 /**
  * cros_read_buf() - Read information into a buf and parse it
  *
  * @bflow: Bootflow to update
  * @buf: Buffer to use
  * @size: Size of buffer and number of bytes to read thereinto
  * @start: Start offset to read from on disk
  * @before_base: Number of bytes to read before the bootloader base
  * @uuid: UUID string if supported, else NULL
  * Return: 0 if OK, -ENOMEM if out of memory, -EIO on read failure
  */
 static int cros_read_buf(struct bootflow *bflow, void *buf, ulong size,
 			 loff_t start, ulong before_base, const char *uuid)
 {
 	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
 	ulong base, setup, cmdline, kern_base;
 	ulong num_blks;
 	int ret;

 	num_blks = size >> desc->log2blksz;
 	log_debug("Reading info to %lx, blk=%s, size=%lx, blocks=%lx\n",
 		  (ulong)map_to_sysmem(buf), bflow->blk->name, size, num_blks);
 	ret = blk_read(bflow->blk, start, num_blks, buf);
 	if (ret != num_blks)
 		return log_msg_ret("inf", -EIO);
 	base = map_to_sysmem(buf) + before_base;

 	setup = base + X86_SETUP_OFFSET;
 	cmdline = base + CMDLINE_OFFSET;
 	kern_base = base + X86_KERNEL_OFFSET;
 	log_debug("base %lx setup %lx cmdline %lx kern_base %lx\n", base,
 		  setup, cmdline, kern_base);

 #ifdef CONFIG_X86
 	const char *version;

 	version = zimage_get_kernel_version(map_sysmem(setup, 0),
 					    map_sysmem(kern_base, 0));
 	log_debug("version %s\n", version);
 	if (version)
 		bflow->name = strdup(version);
 #endif
 	if (!bflow->name)
 		bflow->name = strdup("ChromeOS");
 	if (!bflow->name)
 		return log_msg_ret("nam", -ENOMEM);
 	bflow->os_name = strdup("ChromeOS");
 	if (!bflow->os_name)
 		return log_msg_ret("os", -ENOMEM);

 	ret = copy_cmdline(map_sysmem(cmdline, 0), uuid, &bflow->cmdline);
 	if (ret)
 		return log_msg_ret("cmd", ret);
 	bflow->x86_setup = map_sysmem(setup, 0);

 	return 0;
 }

 /**
  * cros_read_info() - Read information and fill out the bootflow
  *
  * @bflow: Bootflow to update
  * @uuid: UUID string if supported, else NULL
  * @preamble: Kernel preamble information
  * Return: 0 if OK, -ENOMEM if out of memory, -EIO on read failure
  */
 static int cros_read_info(struct bootflow *bflow, const char *uuid,
 			  const struct vb2_kernel_preamble *preamble)
 {
 	struct cros_priv *priv = bflow->bootmeth_priv;
 	struct udevice *blk = bflow->blk;
 	struct blk_desc *desc = dev_get_uclass_plat(blk);
 	ulong offset, size, before_base;
 	void *buf;
 	int ret;

 	log_debug("Kernel preamble at %lx, version major %x, minor %x\n",
 		  (ulong)map_to_sysmem(preamble),
 		  preamble->header_version_major,
 		  preamble->header_version_minor);

 	log_debug("  - load_address %lx, bl_addr %lx, bl_size %lx\n",
 		  (ulong)preamble->body_load_address,
 		  (ulong)preamble->bootloader_address,
 		  (ulong)preamble->bootloader_size);

 	priv->body_size = preamble->body_signature.data_size;
 	priv->body_load_address = preamble->body_load_address;
 	priv->bootloader_address = preamble->bootloader_address;
 	priv->bootloader_size = preamble->bootloader_size;
 	log_debug("Kernel body at %lx size %lx\n", priv->body_offset,
 		  priv->body_size);

 	/* Work out how many bytes to read before the bootloader base */
 	before_base = -CMDLINE_OFFSET;

 	/* Read the cmdline through to the end of the bootloader */
 	size = priv->bootloader_size + before_base;
 	offset = priv->body_offset +
 		(priv->bootloader_address - priv->body_load_address) +
 		CMDLINE_OFFSET;
 	buf = malloc(size);
 	if (!buf)
 		return log_msg_ret("buf", -ENOMEM);

 	ret = cros_read_buf(bflow, buf, size,
 			    priv->part_start + (offset >> desc->log2blksz),
 			    before_base, uuid);
 	if (ret) {
 		/* Clear this since the buffer is invalid */
 		bflow->x86_setup = NULL;
 		free(buf);
 		return log_msg_ret("pro", ret);
 	}
 	priv->info_buf = buf;

 	return 0;
 }

 static int cros_read_kernel(struct bootflow *bflow)
 {
 	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
 	struct cros_priv *priv = bflow->bootmeth_priv;
 	ulong base, setup;
 	ulong num_blks;
 	void *buf;
 	int ret;

 	bflow->size = priv->body_size;

 	buf = memalign(SZ_1K, priv->body_size);
 	if (!buf)
 		return log_msg_ret("buf", -ENOMEM);

 	/* Check that the header is not smaller than permitted */
 	if (priv->body_offset < PROBE_SIZE)
 		return log_msg_ret("san", EFAULT);

 	/* Read kernel body */
 	num_blks = priv->body_size >> desc->log2blksz;
 	log_debug("Reading body to %lx, blk=%s, size=%lx, blocks=%lx\n",
 		  (ulong)map_to_sysmem(buf), bflow->blk->name, priv->body_size,
 		  num_blks);
 	ret = blk_read(bflow->blk,
 		       priv->part_start + (priv->body_offset >> desc->log2blksz),
 		       num_blks, buf);
 	if (ret != num_blks)
 		return log_msg_ret("inf", -EIO);
 	base = map_to_sysmem(buf) + priv->bootloader_address -
 		priv->body_load_address;
 	setup = base + X86_SETUP_OFFSET;

 	bflow->buf = buf;
 	bflow->x86_setup = map_sysmem(setup, 0);

 	return 0;
 }

 static int cros_read_bootflow(struct udevice *dev, struct bootflow *bflow)
 {
 	const struct vb2_kernel_preamble *preamble;
 	struct disk_partition info;
 	struct vb2_keyblock *hdr;
 	const char *uuid = NULL;
 	struct cros_priv *priv;
 	int ret;

 	log_debug("starting, part=%x\n", bflow->part);

 	/* Check for kernel partitions */
 	ret = scan_part(bflow->blk, bflow->part, &info, &hdr);
 	if (ret) {
 		log_debug("- scan failed: err=%d\n", ret);
 		return log_msg_ret("scan", ret);
 	}

 	priv = malloc(sizeof(struct cros_priv));
 	if (!priv) {
 		free(hdr);
 		return log_msg_ret("buf", -ENOMEM);
 	}
 	bflow->bootmeth_priv = priv;

 	log_debug("Selected partition %d, header at %lx\n", bflow->part,
 		  (ulong)map_to_sysmem(hdr));

 	/* Grab a few things from the preamble */
 	preamble = (void *)hdr + hdr->keyblock_size;
 	priv->body_offset = hdr->keyblock_size + preamble->preamble_size;
 	priv->part_start = info.start;

 	/* Now read everything we can learn about kernel */
 #if CONFIG_IS_ENABLED(PARTITION_UUIDS)
 	uuid = info.uuid;
 #endif
 	ret = cros_read_info(bflow, uuid, preamble);
 	preamble = NULL;
 	free(hdr);
 	if (ret) {
 		free(priv->info_buf);
 		free(priv);
 		return log_msg_ret("inf", ret);
 	}
 	bflow->size = priv->body_size;
 	bflow->state = BOOTFLOWST_READY;

 	return 0;
 }

 static int cros_read_file(struct udevice *dev, struct bootflow *bflow,
 			 const char *file_path, ulong addr, ulong *sizep)
 {
 	return -ENOSYS;
 }

 #if CONFIG_IS_ENABLED(BOOTSTD_FULL)
 static int cros_read_all(struct udevice *dev, struct bootflow *bflow)
 {
 	int ret;

 	if (bflow->buf)
 		return log_msg_ret("ld", -EALREADY);
 	ret = cros_read_kernel(bflow);
 	if (ret)
 		return log_msg_ret("rd", ret);

 	return 0;
 }
 #endif /* BOOTSTD_FULL */

 static int cros_boot(struct udevice *dev, struct bootflow *bflow)
 {
 	int ret;

 	if (!bflow->buf) {
 		ret = cros_read_kernel(bflow);
 		if (ret)
 			return log_msg_ret("rd", ret);
 	}

 	if (IS_ENABLED(CONFIG_X86)) {
 		ret = zboot_run(map_to_sysmem(bflow->buf), bflow->size, 0, 0,
 				map_to_sysmem(bflow->x86_setup),
 				bflow->cmdline);
 	} else {
 		ret = bootm_boot_start(map_to_sysmem(bflow->buf),
 				       bflow->cmdline);
 	}

 	return log_msg_ret("go", ret);
 }

 static int cros_bootmeth_bind(struct udevice *dev)
 {
 	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);

 	plat->desc = "ChromiumOS boot";
 	plat->flags = BOOTMETHF_ANY_PART;

 	return 0;
 }

 static struct bootmeth_ops cros_bootmeth_ops = {
 	.check		= cros_check,
 	.read_bootflow	= cros_read_bootflow,
 	.read_file	= cros_read_file,
 	.boot		= cros_boot,
 #if CONFIG_IS_ENABLED(BOOTSTD_FULL)
 	.read_all	= cros_read_all,
 #endif /* BOOTSTD_FULL */
 };

 static const struct udevice_id cros_bootmeth_ids[] = {
 	{ .compatible = "u-boot,cros" },
 	{ }
 };

 U_BOOT_DRIVER(bootmeth_cros) = {
 	.name		= "bootmeth_cros",
 	.id		= UCLASS_BOOTMETH,
 	.of_match	= cros_bootmeth_ids,
 	.ops		= &cros_bootmeth_ops,
 	.bind		= cros_bootmeth_bind,
 };
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Bootmethod for ChromiumOS
	*
	* Copyright 2023 Google LLC
	* Written by Simon Glass <sjg@chromium.org>
	*/

	#define LOG_CATEGORY UCLASS_BOOTSTD

	#include <blk.h>
	#include <bootdev.h>
	#include <bootflow.h>
	#include <bootm.h>
	#include <bootmeth.h>
	#include <display_options.h>
	#include <dm.h>
	#include <efi.h>
	#include <malloc.h>
	#include <mapmem.h>
	#include <part.h>
	#include <linux/sizes.h>
	#include "bootmeth_cros.h"

	static const efi_guid_t cros_kern_type = PARTITION_CROS_KERNEL;

	/*
	* Layout of the ChromeOS kernel
	*
	* Partitions 2 and 4 contain kernels with type GUID_CROS_KERNEL
	*
	* Contents are:
	*
	* Offset Contents
	* 0 struct vb2_keyblock
	* m struct vb2_kernel_preamble
	* m + n kernel buffer
	*
	* m is keyblock->keyblock_size
	* n is preamble->preamble_size
	*
	* The kernel buffer itself consists of various parts:
	*
	* Offset Contents
	* m + n kernel image (Flat vmlinux binary or FIT)
	* b - 8KB Command line text
	* b - 4KB X86 setup block (struct boot_params, extends for about 16KB)
	* b X86 bootloader (continuation of setup block)
	* b + 16KB X86 setup block (copy, used for hold data pointed to)
	*
	* b is m + n + preamble->bootloader_address - preamble->body_load_address
	*
	* Useful metadata extends from b - 8KB through to b + 32 KB
	*/

	enum {
	PROBE_SIZE = SZ_4K, /* initial bytes read from partition */

	X86_SETUP_OFFSET = -0x1000, /* setup offset relative to base */
	CMDLINE_OFFSET = -0x2000, /* cmdline offset relative to base */
	X86_KERNEL_OFFSET = 0x4000, /* kernel offset relative to base */
	};

	/**
	* struct cros_priv - Private data
	*
	* This is read from the disk and recorded for use when the full kernel must
	* be loaded and booted
	*
	* @body_offset: Offset of kernel body from start of partition (in bytes)
	* @body_size: Size of kernel body in bytes
	* @part_start: Block offset of selected partition from the start of the disk
	* @body_load_address: Nominal load address for kernel body
	* @bootloader_address: Address of bootloader, after body is loaded at
	* body_load_address
	* @bootloader_size: Size of bootloader in bytes
	* @info_buf: Buffer containing ChromiumOS info
	*/
	struct cros_priv {
	ulong body_offset;
	ulong body_size;
	lbaint_t part_start;
	ulong body_load_address;
	ulong bootloader_address;
	ulong bootloader_size;
	void *info_buf;
	};

	static int cros_check(struct udevice dev, struct bootflow_iter iter)
	{
	/* This only works on block and network devices */
	if (bootflow_iter_check_blk(iter))
	return log_msg_ret("blk", -ENOTSUPP);

	return 0;
	}

	static int copy_cmdline(const char from, const char uuid, char **bufp)
	{
	const int maxlen = 2048;
	char buf[maxlen];
	char cmd, to, *end;
	int len;

	/* Allow space for cmdline + UUID */
	len = strnlen(from, sizeof(buf));
	if (len >= maxlen)
	return -E2BIG;

	log_debug("uuid %d %s\n", uuid ? (int)strlen(uuid) : 0, uuid);
	for (to = buf, end = buf + maxlen - UUID_STR_LEN - 1; *from; from++) {
	if (to >= end)
	return -E2BIG;
	if (from[0] == '%' && from[1] == 'U' && uuid &&
	strlen(uuid) == UUID_STR_LEN) {
	strcpy(to, uuid);
	to += UUID_STR_LEN;
	from++;
	} else {
	to++ = from;
	}
	}
	*to = '\0';
	len = to - buf;
	cmd = strdup(buf);
	if (!cmd)
	return -ENOMEM;
	free(*bufp);
	*bufp = cmd;

	return 0;
	}

	/**
	* scan_part() - Scan a kernel partition to see if has a ChromeOS header
	*
	* This reads the first PROBE_SIZE of a partition, loookng for
	* VB2_KEYBLOCK_MAGIC
	*
	* @blk: Block device to scan
	* @partnum: Partition number to scan
	* @info: Please to put partition info
	* @hdrp: Return allocated keyblock header on success
	*/
	static int scan_part(struct udevice *blk, int partnum,
	struct disk_partition info, struct vb2_keyblock *hdrp)
	{
	struct blk_desc *desc = dev_get_uclass_plat(blk);
	struct vb2_keyblock *hdr;
	efi_guid_t type;
	ulong num_blks;
	int ret;

	if (!partnum)
	return log_msg_ret("efi", -ENOENT);

	ret = part_get_info(desc, partnum, info);
	if (ret)
	return log_msg_ret("part", ret);

	/* Check for kernel partition type */
	log_debug("part %x: type=%s\n", partnum, info->type_guid);
	if (uuid_str_to_bin(info->type_guid, type.b, UUID_STR_FORMAT_GUID))
	return log_msg_ret("typ", -EINVAL);

	if (guidcmp(&cros_kern_type, &type))
	return log_msg_ret("typ", -ENOEXEC);

	/* Make a buffer for the header information */
	num_blks = PROBE_SIZE >> desc->log2blksz;
	log_debug("Reading header, blk=%s, start=%lx, blocks=%lx\n",
	blk->name, (ulong)info->start, num_blks);
	hdr = memalign(SZ_1K, PROBE_SIZE);
	if (!hdr)
	return log_msg_ret("hdr", -ENOMEM);
	ret = blk_read(blk, info->start, num_blks, hdr);
	if (ret != num_blks) {
	free(hdr);
	return log_msg_ret("inf", -EIO);
	}

	if (memcmp(VB2_KEYBLOCK_MAGIC, hdr->magic, VB2_KEYBLOCK_MAGIC_SIZE)) {
	free(hdr);
	log_debug("no magic\n");
	return -ENOENT;
	}

	*hdrp = hdr;

	return 0;
	}

	/**
	* cros_read_buf() - Read information into a buf and parse it
	*
	* @bflow: Bootflow to update
	* @buf: Buffer to use
	* @size: Size of buffer and number of bytes to read thereinto
	* @start: Start offset to read from on disk
	* @before_base: Number of bytes to read before the bootloader base
	* @uuid: UUID string if supported, else NULL
	* Return: 0 if OK, -ENOMEM if out of memory, -EIO on read failure
	*/
	static int cros_read_buf(struct bootflow bflow, void buf, ulong size,
	loff_t start, ulong before_base, const char *uuid)
	{
	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
	ulong base, setup, cmdline, kern_base;
	ulong num_blks;
	int ret;

	num_blks = size >> desc->log2blksz;
	log_debug("Reading info to %lx, blk=%s, size=%lx, blocks=%lx\n",
	(ulong)map_to_sysmem(buf), bflow->blk->name, size, num_blks);
	ret = blk_read(bflow->blk, start, num_blks, buf);
	if (ret != num_blks)
	return log_msg_ret("inf", -EIO);
	base = map_to_sysmem(buf) + before_base;

	setup = base + X86_SETUP_OFFSET;
	cmdline = base + CMDLINE_OFFSET;
	kern_base = base + X86_KERNEL_OFFSET;
	log_debug("base %lx setup %lx cmdline %lx kern_base %lx\n", base,
	setup, cmdline, kern_base);

	#ifdef CONFIG_X86
	const char *version;

	version = zimage_get_kernel_version(map_sysmem(setup, 0),
	map_sysmem(kern_base, 0));
	log_debug("version %s\n", version);
	if (version)
	bflow->name = strdup(version);
	#endif
	if (!bflow->name)
	bflow->name = strdup("ChromeOS");
	if (!bflow->name)
	return log_msg_ret("nam", -ENOMEM);
	bflow->os_name = strdup("ChromeOS");
	if (!bflow->os_name)
	return log_msg_ret("os", -ENOMEM);

	ret = copy_cmdline(map_sysmem(cmdline, 0), uuid, &bflow->cmdline);
	if (ret)
	return log_msg_ret("cmd", ret);
	bflow->x86_setup = map_sysmem(setup, 0);

	return 0;
	}

	/**
	* cros_read_info() - Read information and fill out the bootflow
	*
	* @bflow: Bootflow to update
	* @uuid: UUID string if supported, else NULL
	* @preamble: Kernel preamble information
	* Return: 0 if OK, -ENOMEM if out of memory, -EIO on read failure
	*/
	static int cros_read_info(struct bootflow bflow, const char uuid,
	const struct vb2_kernel_preamble *preamble)
	{
	struct cros_priv *priv = bflow->bootmeth_priv;
	struct udevice *blk = bflow->blk;
	struct blk_desc *desc = dev_get_uclass_plat(blk);
	ulong offset, size, before_base;
	void *buf;
	int ret;

	log_debug("Kernel preamble at %lx, version major %x, minor %x\n",
	(ulong)map_to_sysmem(preamble),
	preamble->header_version_major,
	preamble->header_version_minor);

	log_debug(" - load_address %lx, bl_addr %lx, bl_size %lx\n",
	(ulong)preamble->body_load_address,
	(ulong)preamble->bootloader_address,
	(ulong)preamble->bootloader_size);

	priv->body_size = preamble->body_signature.data_size;
	priv->body_load_address = preamble->body_load_address;
	priv->bootloader_address = preamble->bootloader_address;
	priv->bootloader_size = preamble->bootloader_size;
	log_debug("Kernel body at %lx size %lx\n", priv->body_offset,
	priv->body_size);

	/* Work out how many bytes to read before the bootloader base */
	before_base = -CMDLINE_OFFSET;

	/* Read the cmdline through to the end of the bootloader */
	size = priv->bootloader_size + before_base;
	offset = priv->body_offset +
	(priv->bootloader_address - priv->body_load_address) +
	CMDLINE_OFFSET;
	buf = malloc(size);
	if (!buf)
	return log_msg_ret("buf", -ENOMEM);

	ret = cros_read_buf(bflow, buf, size,
	priv->part_start + (offset >> desc->log2blksz),
	before_base, uuid);
	if (ret) {
	/* Clear this since the buffer is invalid */
	bflow->x86_setup = NULL;
	free(buf);
	return log_msg_ret("pro", ret);
	}
	priv->info_buf = buf;

	return 0;
	}

	static int cros_read_kernel(struct bootflow *bflow)
	{
	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
	struct cros_priv *priv = bflow->bootmeth_priv;
	ulong base, setup;
	ulong num_blks;
	void *buf;
	int ret;

	bflow->size = priv->body_size;

	buf = memalign(SZ_1K, priv->body_size);
	if (!buf)
	return log_msg_ret("buf", -ENOMEM);

	/* Check that the header is not smaller than permitted */
	if (priv->body_offset < PROBE_SIZE)
	return log_msg_ret("san", EFAULT);

	/* Read kernel body */
	num_blks = priv->body_size >> desc->log2blksz;
	log_debug("Reading body to %lx, blk=%s, size=%lx, blocks=%lx\n",
	(ulong)map_to_sysmem(buf), bflow->blk->name, priv->body_size,
	num_blks);
	ret = blk_read(bflow->blk,
	priv->part_start + (priv->body_offset >> desc->log2blksz),
	num_blks, buf);
	if (ret != num_blks)
	return log_msg_ret("inf", -EIO);
	base = map_to_sysmem(buf) + priv->bootloader_address -
	priv->body_load_address;
	setup = base + X86_SETUP_OFFSET;

	bflow->buf = buf;
	bflow->x86_setup = map_sysmem(setup, 0);

	return 0;
	}

	static int cros_read_bootflow(struct udevice dev, struct bootflow bflow)
	{
	const struct vb2_kernel_preamble *preamble;
	struct disk_partition info;
	struct vb2_keyblock *hdr;
	const char *uuid = NULL;
	struct cros_priv *priv;
	int ret;

	log_debug("starting, part=%x\n", bflow->part);

	/* Check for kernel partitions */
	ret = scan_part(bflow->blk, bflow->part, &info, &hdr);
	if (ret) {
	log_debug("- scan failed: err=%d\n", ret);
	return log_msg_ret("scan", ret);
	}

	priv = malloc(sizeof(struct cros_priv));
	if (!priv) {
	free(hdr);
	return log_msg_ret("buf", -ENOMEM);
	}
	bflow->bootmeth_priv = priv;

	log_debug("Selected partition %d, header at %lx\n", bflow->part,
	(ulong)map_to_sysmem(hdr));

	/* Grab a few things from the preamble */
	preamble = (void *)hdr + hdr->keyblock_size;
	priv->body_offset = hdr->keyblock_size + preamble->preamble_size;
	priv->part_start = info.start;

	/* Now read everything we can learn about kernel */
	#if CONFIG_IS_ENABLED(PARTITION_UUIDS)
	uuid = info.uuid;
	#endif
	ret = cros_read_info(bflow, uuid, preamble);
	preamble = NULL;
	free(hdr);
	if (ret) {
	free(priv->info_buf);
	free(priv);
	return log_msg_ret("inf", ret);
	}
	bflow->size = priv->body_size;
	bflow->state = BOOTFLOWST_READY;

	return 0;
	}

	static int cros_read_file(struct udevice dev, struct bootflow bflow,
	const char file_path, ulong addr, ulong sizep)
	{
	return -ENOSYS;
	}

	#if CONFIG_IS_ENABLED(BOOTSTD_FULL)
	static int cros_read_all(struct udevice dev, struct bootflow bflow)
	{
	int ret;

	if (bflow->buf)
	return log_msg_ret("ld", -EALREADY);
	ret = cros_read_kernel(bflow);
	if (ret)
	return log_msg_ret("rd", ret);

	return 0;
	}
	#endif /* BOOTSTD_FULL */

	static int cros_boot(struct udevice dev, struct bootflow bflow)
	{
	int ret;

	if (!bflow->buf) {
	ret = cros_read_kernel(bflow);
	if (ret)
	return log_msg_ret("rd", ret);
	}

	if (IS_ENABLED(CONFIG_X86)) {
	ret = zboot_run(map_to_sysmem(bflow->buf), bflow->size, 0, 0,
	map_to_sysmem(bflow->x86_setup),
	bflow->cmdline);
	} else {
	ret = bootm_boot_start(map_to_sysmem(bflow->buf),
	bflow->cmdline);
	}

	return log_msg_ret("go", ret);
	}

	static int cros_bootmeth_bind(struct udevice *dev)
	{
	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);

	plat->desc = "ChromiumOS boot";
	plat->flags = BOOTMETHF_ANY_PART;

	return 0;
	}

	static struct bootmeth_ops cros_bootmeth_ops = {
	.check = cros_check,
	.read_bootflow = cros_read_bootflow,
	.read_file = cros_read_file,
	.boot = cros_boot,
	#if CONFIG_IS_ENABLED(BOOTSTD_FULL)
	.read_all = cros_read_all,
	#endif /* BOOTSTD_FULL */
	};

	static const struct udevice_id cros_bootmeth_ids[] = {
	{ .compatible = "u-boot,cros" },
	{ }
	};

	U_BOOT_DRIVER(bootmeth_cros) = {
	.name = "bootmeth_cros",
	.id = UCLASS_BOOTMETH,
	.of_match = cros_bootmeth_ids,
	.ops = &cros_bootmeth_ops,
	.bind = cros_bootmeth_bind,
	};