cmd: Add 'bcb' command to read/modify/write BCB fields

'Bootloader Control Block' (BCB) is a well established term/acronym in
the Android namespace which refers to a location in a dedicated raw
(i.e. FS-unaware) flash (e.g. eMMC) partition, usually called "misc",
which is used as media for exchanging messages between Android userspace
(particularly recovery [1]) and an Android-capable bootloader.

On higher level, this allows implementing a subset of Android Bootloader
Requirements [2], amongst which is the Android-specific bootloader
flow [3]. Regardless how the latter is implemented in U-Boot ([3] being
the most memorable example), reading/writing/dumping the BCB fields in
the development process from inside the U-Boot is a convenient feature.
Hence, make it available to the users.

Some usage examples of the new command recorded on R-Car H3ULCB-KF
('>>>' is an overlay on top of the original console output):

=> bcb
bcb - Load/set/clear/test/dump/store Android BCB fields

Usage:
bcb load  <dev> <part>       - load  BCB from mmc <dev>:<part>
bcb set   <field> <val>      - set   BCB <field> to <val>
bcb clear [<field>]          - clear BCB <field> or all fields
bcb test  <field> <op> <val> - test  BCB <field> against <val>
bcb dump  <field>            - dump  BCB <field>
bcb store                    - store BCB back to mmc

Legend:
<dev>   - MMC device index containing the BCB partition
<part>  - MMC partition index or name containing the BCB
<field> - one of {command,status,recovery,stage,reserved}
<op>    - the binary operator used in 'bcb test':
          '=' returns true if <val> matches the string stored in <field>
          '~' returns true if <val> matches a subset of <field>'s string
<val>   - string/text provided as input to bcb {set,test}
          NOTE: any ':' character in <val> will be replaced by line feed
          during 'bcb set' and used as separator by upper layers

=> bcb dump command
Error: Please, load BCB first!
 >>> Users must specify mmc device and partition before any other call

=> bcb load 1 misc
=> bcb load 1 1
 >>> The two calls are equivalent (assuming "misc" has index 1)

=> bcb dump command
00000000: 62 6f 6f 74 6f 6e 63 65 2d 73 68 65 6c 6c 00 72    bootonce-shell.r
00000010: 79 00 72 00 00 00 00 00 00 00 00 00 00 00 00 00    y.r.............
 >>> The output is in binary/string format for convenience
 >>> The output size matches the size of inspected BCB field
 >>> (32 bytes in case of 'command')

=> bcb test command = bootonce-shell && echo true
true
=> bcb test command = bootonce-shell- && echo true
=> bcb test command = bootonce-shel && echo true
 >>> The '=' operator returns 'true' on perfect match

=> bcb test command ~ bootonce-shel && echo true
true
=> bcb test command ~ bootonce-shell && echo true
true
 >>> The '~' operator returns 'true' on substring match

=> bcb set command recovery
=> bcb dump command
00000000: 72 65 63 6f 76 65 72 79 00 73 68 65 6c 6c 00 72    recovery.shell.r
00000010: 79 00 72 00 00 00 00 00 00 00 00 00 00 00 00 00    y.r.............
 >>> The new value is NULL-terminated and stored in the BCB field

=> bcb set recovery "msg1:msg2:msg3"
=> bcb dump recovery
00000040: 6d 73 67 31 0a 6d 73 67 32 0a 6d 73 67 33 00 00    msg1.msg2.msg3..
00000050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
00000060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
 >>> --- snip ---
 >>> Every ':' is replaced by line-feed '\n' (0xA). The latter is used
 >>> as separator between individual commands by Android userspace

=> bcb store
 >>> Flush/store the BCB structure to MMC

[1] https://android.googlesource.com/platform/bootable/recovery
[2] https://source.android.com/devices/bootloader
[3] https://patchwork.ozlabs.org/patch/746835/
    ("[U-Boot,5/6] Initial support for the Android Bootloader flow")

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>

3 files changed, 358 insertions, 0 deletions

diff --git a/cmd/Kconfig b/cmd/Kconfig
index cda7931fe3..3afb760a81 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -631,6 +631,23 @@ config CMD_ADC
 	  Shows ADC device info and permit printing one-shot analog converted
 	  data from a named Analog to Digital Converter.
 
+config CMD_BCB
+	bool "bcb"
+	depends on MMC
+	depends on PARTITIONS
+	help
+	  Read/modify/write the fields of Bootloader Control Block, usually
+	  stored on the flash "misc" partition with its structure defined in:
+	  https://android.googlesource.com/platform/bootable/recovery/+/master/
+	  bootloader_message/include/bootloader_message/bootloader_message.h
+
+	  Some real-life use-cases include (but are not limited to):
+	  - Determine the "boot reason" (and act accordingly):
+	    https://source.android.com/devices/bootloader/boot-reason
+	  - Get/pass a list of commands from/to recovery:
+	    https://android.googlesource.com/platform/bootable/recovery
+	  - Inspect/dump the contents of the BCB fields
+
 config CMD_BIND
 	bool "bind/unbind - Bind or unbind a device to/from a driver"
 	depends on DM
diff --git a/cmd/Makefile b/cmd/Makefile
index f982564ab9..49e64cde1d 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_CMD_ADC) += adc.o
 obj-$(CONFIG_CMD_ARMFLASH) += armflash.o
 obj-y += blk_common.o
 obj-$(CONFIG_CMD_SOURCE) += source.o
+obj-$(CONFIG_CMD_BCB) += bcb.o
 obj-$(CONFIG_CMD_BDI) += bdinfo.o
 obj-$(CONFIG_CMD_BEDBUG) += bedbug.o
 obj-$(CONFIG_CMD_BIND) += bind.o
diff --git a/cmd/bcb.c b/cmd/bcb.c
new file mode 100644
index 0000000000..2bd5a744de
--- /dev/null
+++ b/cmd/bcb.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 Eugeniu Rosca <rosca.eugeniu@gmail.com>
+ *
+ * Command to read/modify/write Android BCB fields
+ */
+
+#include <android_bootloader_message.h>
+#include <command.h>
+#include <common.h>
+
+enum bcb_cmd {
+	BCB_CMD_LOAD,
+	BCB_CMD_FIELD_SET,
+	BCB_CMD_FIELD_CLEAR,
+	BCB_CMD_FIELD_TEST,
+	BCB_CMD_FIELD_DUMP,
+	BCB_CMD_STORE,
+};
+
+static int bcb_dev = -1;
+static int bcb_part = -1;
+static struct bootloader_message bcb = { { 0 } };
+
+static int bcb_cmd_get(char *cmd)
+{
+	if (!strncmp(cmd, "load", sizeof("load")))
+		return BCB_CMD_LOAD;
+	if (!strncmp(cmd, "set", sizeof("set")))
+		return BCB_CMD_FIELD_SET;
+	if (!strncmp(cmd, "clear", sizeof("clear")))
+		return BCB_CMD_FIELD_CLEAR;
+	if (!strncmp(cmd, "test", sizeof("test")))
+		return BCB_CMD_FIELD_TEST;
+	if (!strncmp(cmd, "store", sizeof("store")))
+		return BCB_CMD_STORE;
+	if (!strncmp(cmd, "dump", sizeof("dump")))
+		return BCB_CMD_FIELD_DUMP;
+	else
+		return -1;
+}
+
+static int bcb_is_misused(int argc, char *const argv[])
+{
+	int cmd = bcb_cmd_get(argv[0]);
+
+	switch (cmd) {
+	case BCB_CMD_LOAD:
+		if (argc != 3)
+			goto err;
+		break;
+	case BCB_CMD_FIELD_SET:
+		if (argc != 3)
+			goto err;
+		break;
+	case BCB_CMD_FIELD_TEST:
+		if (argc != 4)
+			goto err;
+		break;
+	case BCB_CMD_FIELD_CLEAR:
+		if (argc != 1 && argc != 2)
+			goto err;
+		break;
+	case BCB_CMD_STORE:
+		if (argc != 1)
+			goto err;
+		break;
+	case BCB_CMD_FIELD_DUMP:
+		if (argc != 2)
+			goto err;
+		break;
+	default:
+		printf("Error: 'bcb %s' not supported\n", argv[0]);
+		return -1;
+	}
+
+	if (cmd != BCB_CMD_LOAD && (bcb_dev < 0 || bcb_part < 0)) {
+		printf("Error: Please, load BCB first!\n");
+		return -1;
+	}
+
+	return 0;
+err:
+	printf("Error: Bad usage of 'bcb %s'\n", argv[0]);
+
+	return -1;
+}
+
+static int bcb_field_get(char *name, char **field, int *size)
+{
+	if (!strncmp(name, "command", sizeof("command"))) {
+		*field = bcb.command;
+		*size = sizeof(bcb.command);
+	} else if (!strncmp(name, "status", sizeof("status"))) {
+		*field = bcb.status;
+		*size = sizeof(bcb.status);
+	} else if (!strncmp(name, "recovery", sizeof("recovery"))) {
+		*field = bcb.recovery;
+		*size = sizeof(bcb.recovery);
+	} else if (!strncmp(name, "stage", sizeof("stage"))) {
+		*field = bcb.stage;
+		*size = sizeof(bcb.stage);
+	} else if (!strncmp(name, "reserved", sizeof("reserved"))) {
+		*field = bcb.reserved;
+		*size = sizeof(bcb.reserved);
+	} else {
+		printf("Error: Unknown bcb field '%s'\n", name);
+		return -1;
+	}
+
+	return 0;
+}
+
+static int
+do_bcb_load(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	struct blk_desc *desc;
+	disk_partition_t info;
+	u64 cnt;
+	char *endp;
+	int part, ret;
+
+	ret = blk_get_device_by_str("mmc", argv[1], &desc);
+	if (ret < 0)
+		goto err_1;
+
+	part = simple_strtoul(argv[2], &endp, 0);
+	if (*endp == '\0') {
+		ret = part_get_info(desc, part, &info);
+		if (ret)
+			goto err_1;
+	} else {
+		part = part_get_info_by_name(desc, argv[2], &info);
+		if (part < 0) {
+			ret = part;
+			goto err_1;
+		}
+	}
+
+	cnt = DIV_ROUND_UP(sizeof(struct bootloader_message), info.blksz);
+	if (cnt > info.size)
+		goto err_2;
+
+	if (blk_dread(desc, info.start, cnt, &bcb) != cnt) {
+		ret = -EIO;
+		goto err_1;
+	}
+
+	bcb_dev = desc->devnum;
+	bcb_part = part;
+	debug("%s: Loaded from mmc %d:%d\n", __func__, bcb_dev, bcb_part);
+
+	return CMD_RET_SUCCESS;
+err_1:
+	printf("Error: mmc %s:%s read failed (%d)\n", argv[1], argv[2], ret);
+	goto err;
+err_2:
+	printf("Error: mmc %s:%s too small!", argv[1], argv[2]);
+	goto err;
+err:
+	bcb_dev = -1;
+	bcb_part = -1;
+
+	return CMD_RET_FAILURE;
+}
+
+static int do_bcb_set(cmd_tbl_t *cmdtp, int flag, int argc,
+		      char * const argv[])
+{
+	int size, len;
+	char *field, *str, *found;
+
+	if (bcb_field_get(argv[1], &field, &size))
+		return CMD_RET_FAILURE;
+
+	len = strlen(argv[2]);
+	if (len >= size) {
+		printf("Error: sizeof('%s') = %d >= %d = sizeof(bcb.%s)\n",
+		       argv[2], len, size, argv[1]);
+		return CMD_RET_FAILURE;
+	}
+	str = argv[2];
+
+	field[0] = '\0';
+	while ((found = strsep(&str, ":"))) {
+		if (field[0] != '\0')
+			strcat(field, "\n");
+		strcat(field, found);
+	}
+
+	return CMD_RET_SUCCESS;
+}
+
+static int do_bcb_clear(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	int size;
+	char *field;
+
+	if (argc == 1) {
+		memset(&bcb, 0, sizeof(bcb));
+		return CMD_RET_SUCCESS;
+	}
+
+	if (bcb_field_get(argv[1], &field, &size))
+		return CMD_RET_FAILURE;
+
+	memset(field, 0, size);
+
+	return CMD_RET_SUCCESS;
+}
+
+static int do_bcb_test(cmd_tbl_t *cmdtp, int flag, int argc,
+		       char * const argv[])
+{
+	int size;
+	char *field;
+	char *op = argv[2];
+
+	if (bcb_field_get(argv[1], &field, &size))
+		return CMD_RET_FAILURE;
+
+	if (*op == '=' && *(op + 1) == '\0') {
+		if (!strncmp(argv[3], field, size))
+			return CMD_RET_SUCCESS;
+		else
+			return CMD_RET_FAILURE;
+	} else if (*op == '~' && *(op + 1) == '\0') {
+		if (!strstr(field, argv[3]))
+			return CMD_RET_FAILURE;
+		else
+			return CMD_RET_SUCCESS;
+	} else {
+		printf("Error: Unknown operator '%s'\n", op);
+	}
+
+	return CMD_RET_FAILURE;
+}
+
+static int do_bcb_dump(cmd_tbl_t *cmdtp, int flag, int argc,
+		       char * const argv[])
+{
+	int size;
+	char *field;
+
+	if (bcb_field_get(argv[1], &field, &size))
+		return CMD_RET_FAILURE;
+
+	print_buffer((ulong)field - (ulong)&bcb, (void *)field, 1, size, 16);
+
+	return CMD_RET_SUCCESS;
+}
+
+static int do_bcb_store(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	struct blk_desc *desc;
+	disk_partition_t info;
+	u64 cnt;
+	int ret;
+
+	desc = blk_get_devnum_by_type(IF_TYPE_MMC, bcb_dev);
+	if (!desc) {
+		ret = -ENODEV;
+		goto err;
+	}
+
+	ret = part_get_info(desc, bcb_part, &info);
+	if (ret)
+		goto err;
+
+	cnt = DIV_ROUND_UP(sizeof(struct bootloader_message), info.blksz);
+
+	if (blk_dwrite(desc, info.start, cnt, &bcb) != cnt) {
+		ret = -EIO;
+		goto err;
+	}
+
+	return CMD_RET_SUCCESS;
+err:
+	printf("Error: mmc %d:%d write failed (%d)\n", bcb_dev, bcb_part, ret);
+
+	return CMD_RET_FAILURE;
+}
+
+static cmd_tbl_t cmd_bcb_sub[] = {
+	U_BOOT_CMD_MKENT(load, CONFIG_SYS_MAXARGS, 1, do_bcb_load, "", ""),
+	U_BOOT_CMD_MKENT(set, CONFIG_SYS_MAXARGS, 1, do_bcb_set, "", ""),
+	U_BOOT_CMD_MKENT(clear, CONFIG_SYS_MAXARGS, 1, do_bcb_clear, "", ""),
+	U_BOOT_CMD_MKENT(test, CONFIG_SYS_MAXARGS, 1, do_bcb_test, "", ""),
+	U_BOOT_CMD_MKENT(dump, CONFIG_SYS_MAXARGS, 1, do_bcb_dump, "", ""),
+	U_BOOT_CMD_MKENT(store, CONFIG_SYS_MAXARGS, 1, do_bcb_store, "", ""),
+};
+
+static int do_bcb(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
+{
+	cmd_tbl_t *c;
+
+	if (argc < 2)
+		return CMD_RET_USAGE;
+
+	argc--;
+	argv++;
+
+	c = find_cmd_tbl(argv[0], cmd_bcb_sub, ARRAY_SIZE(cmd_bcb_sub));
+	if (!c)
+		return CMD_RET_USAGE;
+
+	if (bcb_is_misused(argc, argv)) {
+		/* We try to improve the user experience by reporting the
+		 * root-cause of misusage, so don't return CMD_RET_USAGE,
+		 * since the latter prints out the full-blown help text
+		 */
+		return CMD_RET_FAILURE;
+	}
+
+	return c->cmd(cmdtp, flag, argc, argv);
+}
+
+U_BOOT_CMD(
+	bcb, CONFIG_SYS_MAXARGS, 1, do_bcb,
+	"Load/set/clear/test/dump/store Android BCB fields",
+	"load  <dev> <part>       - load  BCB from mmc <dev>:<part>\n"
+	"bcb set   <field> <val>      - set   BCB <field> to <val>\n"
+	"bcb clear [<field>]          - clear BCB <field> or all fields\n"
+	"bcb test  <field> <op> <val> - test  BCB <field> against <val>\n"
+	"bcb dump  <field>            - dump  BCB <field>\n"
+	"bcb store                    - store BCB back to mmc\n"
+	"\n"
+	"Legend:\n"
+	"<dev>   - MMC device index containing the BCB partition\n"
+	"<part>  - MMC partition index or name containing the BCB\n"
+	"<field> - one of {command,status,recovery,stage,reserved}\n"
+	"<op>    - the binary operator used in 'bcb test':\n"
+	"          '=' returns true if <val> matches the string stored in <field>\n"
+	"          '~' returns true if <val> matches a subset of <field>'s string\n"
+	"<val>   - string/text provided as input to bcb {set,test}\n"
+	"          NOTE: any ':' character in <val> will be replaced by line feed\n"
+	"          during 'bcb set' and used as separator by upper layers\n"
+);