bootstd: Add a simple bootmeth for ChromiumOS

It is possible to boot x86-based ChromeOS machines by parsing a table and
locating the kernel and command line. Add a bootmeth for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

boot/Kconfig

@@ -463,6 +463,17 @@ config BOOTMETH_GLOBAL
 	  EFI bootmgr, since they take full control over which bootdevs are
 	  selected to boot.
 
+config BOOTMETH_CROS
+	bool "Bootdev support for Chromium OS"
+	depends on X86 || SANDBOX
+	default y
+	help
+	  Enables support for booting Chromium OS using bootdevs. This uses the
+	  kernel A slot and obtains the kernel command line from the parameters
+	  provided there.
+
+	  Note that only x86 devices are supported at present.
+
 config BOOTMETH_EXTLINUX
 	bool "Bootdev support for extlinux boot"
 	select PXE_UTILS

boot/Makefile

@@ -27,6 +27,7 @@ obj-$(CONFIG_$(SPL_TPL_)BOOTSTD) += bootstd-uclass.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_EXTLINUX) += bootmeth_extlinux.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_EXTLINUX_PXE) += bootmeth_pxe.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_EFILOADER) += bootmeth_efi.o
+obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_CROS) += bootmeth_cros.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_SANDBOX) += bootmeth_sandbox.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_SCRIPT) += bootmeth_script.o
 ifdef CONFIG_$(SPL_TPL_)BOOTSTD_FULL

boot/bootmeth_cros.c

@@ -0,0 +1,212 @@
+// 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 <common.h>
+#include <blk.h>
+#include <bootdev.h>
+#include <bootflow.h>
+#include <bootmeth.h>
+#include <dm.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <part.h>
+#ifdef CONFIG_X86
+#include <asm/zimage.h>
+#endif
+#include <linux/sizes.h>
+
+enum {
+	/* Offsets in the kernel-partition header */
+	KERN_START	= 0x4f0,
+	KERN_SIZE	= 0x518,
+
+	SETUP_OFFSET	= 0x1000,	/* bytes before base */
+	CMDLINE_OFFSET	= 0x2000,	/* bytes before base */
+	OFFSET_BASE	= 0x100000,	/* assumed kernel load-address */
+};
+
+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;
+}
+
+static int cros_read_bootflow(struct udevice *dev, struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	ulong base, start, size, setup, cmdline, num_blks, kern_base;
+	struct disk_partition info;
+	const char *uuid = NULL;
+	void *buf, *hdr;
+	int ret;
+
+	log_debug("starting, part=%d\n", bflow->part);
+
+	/* We consider the whole disk, not any one partition */
+	if (bflow->part)
+		return log_msg_ret("max", -ENOENT);
+
+	/* Check partition 2 */
+	ret = part_get_info(desc, 2, &info);
+	if (ret)
+		return log_msg_ret("part", ret);
+
+	/* Make a buffer for the header information */
+	num_blks = SZ_4K >> desc->log2blksz;
+	log_debug("Reading header, blk=%s, start=%lx, blocks=%lx\n",
+		  bflow->blk->name, (ulong)info.start, num_blks);
+	hdr = memalign(SZ_1K, SZ_4K);
+	if (!hdr)
+		return log_msg_ret("hdr", -ENOMEM);
+	ret = blk_read(bflow->blk, info.start, num_blks, hdr);
+	if (ret != num_blks)
+		return log_msg_ret("inf", ret);
+
+	if (memcmp("CHROMEOS", hdr, 8))
+		return -ENOENT;
+
+	log_info("Header at %lx\n", (ulong)map_to_sysmem(hdr));
+	start = *(u32 *)(hdr + KERN_START);
+	size = ALIGN(*(u32 *)(hdr + KERN_SIZE), desc->blksz);
+	log_debug("Reading start %lx size %lx\n", start, size);
+	bflow->size = size;
+
+	buf = memalign(SZ_1K, size);
+	if (!buf)
+		return log_msg_ret("buf", -ENOMEM);
+	num_blks = size >> desc->log2blksz;
+	log_debug("Reading data, blk=%s, start=%lx, blocks=%lx\n",
+		  bflow->blk->name, (ulong)info.start, num_blks);
+	ret = blk_read(bflow->blk, (ulong)info.start + 0x80, num_blks, buf);
+	if (ret != num_blks)
+		return log_msg_ret("inf", ret);
+	base = map_to_sysmem(buf);
+
+	setup = base + start - OFFSET_BASE - SETUP_OFFSET;
+	cmdline = base + start - OFFSET_BASE - CMDLINE_OFFSET;
+	kern_base = base + start - OFFSET_BASE + SZ_16K;
+	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);
+
+#if CONFIG_IS_ENABLED(PARTITION_UUIDS)
+	uuid = info.uuid;
+#endif
+	ret = copy_cmdline(map_sysmem(cmdline, 0), uuid, &bflow->cmdline);
+	if (ret)
+		return log_msg_ret("cmd", ret);
+
+	bflow->state = BOOTFLOWST_READY;
+	bflow->buf = buf;
+	bflow->x86_setup = map_sysmem(setup, 0);
+
+	return 0;
+}
+
+static int cros_read_file(struct udevice *dev, struct bootflow *bflow,
+			 const char *file_path, ulong addr, ulong *sizep)
+{
+	return -ENOSYS;
+}
+
+static int cros_boot(struct udevice *dev, struct bootflow *bflow)
+{
+#ifdef CONFIG_X86
+	zboot_start(map_to_sysmem(bflow->buf), bflow->size, 0, 0,
+		    map_to_sysmem(bflow->x86_setup),
+		    bflow->cmdline);
+#endif
+
+	return log_msg_ret("go", -EFAULT);
+}
+
+static int cros_bootmeth_bind(struct udevice *dev)
+{
+	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);
+
+	plat->desc = "ChromiumOS boot";
+
+	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,
+};
+
+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,
+};

configs/tools-only_defconfig

@@ -10,6 +10,7 @@ CONFIG_FIT=y
 CONFIG_TIMESTAMP=y
 CONFIG_FIT_SIGNATURE=y
 # CONFIG_BOOTSTD_FULL is not set
+# CONFIG_BOOTMETH_CROS is not set
 # CONFIG_BOOTMETH_VBE is not set
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run distro_bootcmd"