bootstd: Add an implementation of script boot

Add a bootmeth driver which handles distro boot from a disk via a U-Boot
script, so we can boot a bootflow using this commonly used mechanism. This
is required by Armbian, for example.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/Kconfig

@@ -377,6 +377,17 @@ config BOOTMETH_SANDBOX
 	  This is a sandbox bootmeth driver used for testing. It always returns
 	  -ENOTSUPP when attempting to boot.
 
+config BOOTMETH_SCRIPT
+	bool "Bootdev support for U-Boot scripts"
+	default y if BOOTSTD_FULL
+	help
+	  Enables support for booting a distro via a U-Boot script. This makes
+	  the bootdevs look for a 'boot/boot.scr' file which can be used to
+	  boot the distro.
+
+	  This provides a way to try out standard boot on an existing boot flow.
+	  It is not enabled by default to save space.
+
 endif
 
 config LEGACY_IMAGE_FORMAT

boot/Makefile

@@ -28,6 +28,7 @@ obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_DISTRO) += bootmeth_distro.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_DISTRO_PXE) += bootmeth_pxe.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_EFILOADER) += bootmeth_efi.o
 obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_SANDBOX) += bootmeth_sandbox.o
+obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_SCRIPT) += bootmeth_script.o
 ifdef CONFIG_$(SPL_TPL_)BOOTSTD_FULL
 obj-$(CONFIG_$(SPL_TPL_)CMD_BOOTEFI_BOOTMGR) += bootmeth_efi_mgr.o
 endif

boot/bootmeth_script.c

@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Bootmethod for booting via a U-Boot script
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#define LOG_CATEGORY UCLASS_BOOTSTD
+
+#include <common.h>
+#include <blk.h>
+#include <bootflow.h>
+#include <bootmeth.h>
+#include <bootstd.h>
+#include <dm.h>
+#include <env.h>
+#include <fs.h>
+#include <image.h>
+#include <malloc.h>
+#include <mapmem.h>
+
+#define SCRIPT_FNAME1	"boot.scr.uimg"
+#define SCRIPT_FNAME2	"boot.scr"
+
+static int script_check(struct udevice *dev, struct bootflow_iter *iter)
+{
+	int ret;
+
+	/* This only works on block devices */
+	ret = bootflow_iter_uses_blk_dev(iter);
+	if (ret)
+		return log_msg_ret("blk", ret);
+
+	return 0;
+}
+
+static int script_read_bootflow(struct udevice *dev, struct bootflow *bflow)
+{
+	struct blk_desc *desc = NULL;
+	const char *const *prefixes;
+	struct udevice *bootstd;
+	const char *prefix;
+	int ret, i;
+
+	ret = uclass_first_device_err(UCLASS_BOOTSTD, &bootstd);
+	if (ret)
+		return log_msg_ret("std", ret);
+
+	/* We require a partition table */
+	if (!bflow->part)
+		return -ENOENT;
+
+	if (bflow->blk)
+		 desc = dev_get_uclass_plat(bflow->blk);
+
+	prefixes = bootstd_get_prefixes(bootstd);
+	i = 0;
+	do {
+		prefix = prefixes ? prefixes[i] : NULL;
+
+		ret = bootmeth_try_file(bflow, desc, prefix, SCRIPT_FNAME1);
+		if (ret)
+			ret = bootmeth_try_file(bflow, desc, prefix,
+						SCRIPT_FNAME2);
+	} while (ret && prefixes && prefixes[++i]);
+	if (ret)
+		return log_msg_ret("try", ret);
+
+	bflow->subdir = strdup(prefix ? prefix : "");
+	if (!bflow->subdir)
+		return log_msg_ret("prefix", -ENOMEM);
+
+	ret = bootmeth_alloc_file(bflow, 0x10000, 1);
+	if (ret)
+		return log_msg_ret("read", ret);
+
+	return 0;
+}
+
+static int script_boot(struct udevice *dev, struct bootflow *bflow)
+{
+	struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
+	ulong addr;
+	int ret;
+
+	ret = env_set("devtype", blk_get_devtype(bflow->blk));
+	if (!ret)
+		ret = env_set_hex("devnum", desc->devnum);
+	if (!ret)
+		ret = env_set("prefix", bflow->subdir);
+	if (!ret && IS_ENABLED(CONFIG_ARCH_SUNXI) &&
+	    !strcmp("mmc", blk_get_devtype(bflow->blk)))
+		ret = env_set_hex("mmc_bootdev", desc->devnum);
+	if (ret)
+		return log_msg_ret("env", ret);
+
+	log_debug("devtype: %s\n", env_get("devtype"));
+	log_debug("devnum: %s\n", env_get("devnum"));
+	log_debug("prefix: %s\n", env_get("prefix"));
+	log_debug("mmc_bootdev: %s\n", env_get("mmc_bootdev"));
+
+	addr = map_to_sysmem(bflow->buf);
+	ret = image_source_script(addr, NULL);
+	if (ret)
+		return log_msg_ret("boot", ret);
+
+	return 0;
+}
+
+static int script_bootmeth_bind(struct udevice *dev)
+{
+	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);
+
+	plat->desc = IS_ENABLED(CONFIG_BOOTSTD_FULL) ?
+		"Script boot from a block device" : "script";
+
+	return 0;
+}
+
+static struct bootmeth_ops script_bootmeth_ops = {
+	.check		= script_check,
+	.read_bootflow	= script_read_bootflow,
+	.read_file	= bootmeth_common_read_file,
+	.boot		= script_boot,
+};
+
+static const struct udevice_id script_bootmeth_ids[] = {
+	{ .compatible = "u-boot,script" },
+	{ }
+};
+
+U_BOOT_DRIVER(bootmeth_script) = {
+	.name		= "bootmeth_script",
+	.id		= UCLASS_BOOTMETH,
+	.of_match	= script_bootmeth_ids,
+	.ops		= &script_bootmeth_ops,
+	.bind		= script_bootmeth_bind,
+};