[PATCH 6/6] cmd: Add MBR partition layout control utility

[Heinrich Schuchardt]

Am 17. Dezember 2020 12:27:39 MEZ schrieb Marek Szyprowski <m.szyprowski at samsung.com>:
>Add a 'mbr' command to let user create or verify MBR partition layout
>based on the provided text description. The partition layout is
>altearnatively read from 'mbr_parts' environment variable. This can be
>used in scripts to help system image flashing tools to ensure proper
>partition layout.
>
>The syntax of the text description of the partition list is similar to
>the one used by the 'gpt' command. Supported parameters are: name
>(currently ignored), start (partition start offset in bytes), size (in
>bytes or '-' to expand it to the whole free area), bootable (boolean
>flag)
>and id (MBR partition system ID). If one wants to create more than 4
>partitions, an 'Extended' primary partition (with 0x05 ID) has to be
>explicitely provided as a one of the first 4 entries.
>
>Here is the example how to create a 6 partitions (3 on the 'extended
>volume'), some of the predefined sizes:
>
>> setenv mbr_parts 'name=boot,start=4M,size=128M,bootable,id=0x0e;
>  name=rootfs,size=3072M,id=0x83;
>  name=system-data,size=512M,id=0x83;
>  name=[ext],size=-,id=0x05;
>  name=user,size=-,id=0x83;
>  name=modules,size=100M,id=0x83;
>  name=ramdisk,size=8M,id=0x83'
>> mbr write mmc 0
>
>Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>---
> cmd/Kconfig  |   8 ++
> cmd/Makefile |   1 +
> cmd/mbr.c    | 308 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 317 insertions(+)
> create mode 100644 cmd/mbr.c
>
>diff --git a/cmd/Kconfig b/cmd/Kconfig
>index 1595de999b..2c3358e359 100644
>--- a/cmd/Kconfig
>+++ b/cmd/Kconfig
>@@ -1025,6 +1025,14 @@ config CMD_LSBLK
>	  Print list of available block device drivers, and for each, the list
> 	  of known block devices.
> 
>+config CMD_MBR
>+	bool "MBR (Master Boot Record) command"
>+	select DOS_PARTITION
>+	select HAVE_BLOCK_DEVICE
>+	help
>+	  Enable the 'mbr' command to ready and write MBR (Master Boot
>Record)
>+	  style partition tables.
>+
> config CMD_MISC
> 	bool "misc"
> 	depends on MISC
>diff --git a/cmd/Makefile b/cmd/Makefile
>index dd86675bf2..41379d9a0e 100644
>--- a/cmd/Makefile
>+++ b/cmd/Makefile
>@@ -178,6 +178,7 @@ obj-$(CONFIG_CMD_ZFS) += zfs.o
> 
> obj-$(CONFIG_CMD_DFU) += dfu.o
> obj-$(CONFIG_CMD_GPT) += gpt.o
>+obj-$(CONFIG_CMD_MBR) += mbr.o
> obj-$(CONFIG_CMD_ETHSW) += ethsw.o
> obj-$(CONFIG_CMD_AXI) += axi.o
> obj-$(CONFIG_CMD_PVBLOCK) += pvblock.o
>diff --git a/cmd/mbr.c b/cmd/mbr.c
>new file mode 100644
>index 0000000000..25a3f694d3
>--- /dev/null
>+++ b/cmd/mbr.c
>@@ -0,0 +1,308 @@
>+// SPDX-License-Identifier: GPL-2.0+
>+/*
>+ * cmd_mbr.c -- MBR (Master Boot Record) handling command
>+ *
>+ * Copyright (C) 2020 Samsung Electronics
>+ * author: Marek Szyprowski <m.szyprowski at samsung.com>
>+ *
>+ * based on the gpt command.
>+ */
>+
>+#include <common.h>
>+#include <blk.h>
>+#include <malloc.h>
>+#include <command.h>
>+#include <part.h>
>+
>+/**
>+ * extract_val(): Extract value from a key=value pair list (comma
>separated).
>+ *                Only value for the given key is returend.
>+ *                Function allocates memory for the value, remember to
>free!
>+ *
>+ * @param str - pointer to string with key=values pairs
>+ * @param key - pointer to the key to search for
>+ *
>+ * @return - pointer to allocated string with the value

Please, format your comments as described in

https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation






>+ */
>+static char *extract_val(const char *str, const char *key)
>+{
>+	char *v, *k;
>+	char *s, *strcopy;
>+	char *new = NULL;
>+
>+	strcopy = strdup(str);
>+	if (strcopy == NULL)
>+		return NULL;
>+
>+	s = strcopy;
>+	while (s) {
>+		v = strsep(&s, ",");
>+		if (!v)
>+			break;
>+		k = strsep(&v, "=");
>+		if (!k)
>+			break;
>+		if  (strcmp(k, key) == 0) {
>+			new = strdup(v);
>+			break;
>+		}
>+	}
>+
>+	free(strcopy);
>+
>+	return new;
>+}
>+
>+/**
>+ * found_key(): Found key without value in parameter list (comma
>separated).
>+ *
>+ * @param str - pointer to string with key
>+ * @param key - pointer to the key to search for
>+ *
>+ * @return - true on found key
>+ */
>+static bool found_key(const char *str, const char *key)
>+{
>+	char *k;
>+	char *s, *strcopy;
>+	bool result = false;
>+
>+	strcopy = strdup(str);
>+	if (!strcopy)
>+		return NULL;
>+
>+	s = strcopy;
>+	while (s) {
>+		k = strsep(&s, ",");
>+		if (!k)
>+			break;
>+		if  (strcmp(k, key) == 0) {
>+			result = true;
>+			break;
>+		}
>+	}
>+
>+	free(strcopy);
>+
>+	return result;
>+}
>+
>+static int str_to_partition_info(const char *str_part, unsigned long
>*disk_uuid,
>+			struct disk_partition **partitions, int *parts_count)
>+{
>+	char *tok, *str, *s;
>+	int i;
>+	char *val, *p;
>+	int p_count;
>+	struct disk_partition *parts;
>+	int errno = 0;
>+	uint64_t size_ll, start_ll;
>+
>+	if (str_part == NULL)
>+		return -1;
>+
>+	str = strdup(str_part);
>+	if (str == NULL)
>+		return -ENOMEM;
>+
>+	/* extract disk guid */
>+	s = str;
>+	val = extract_val(str, "uuid_disk");
>+	if (val) {
>+		val = strsep(&val, ";");
>+		p = val;
>+		*disk_uuid = ustrtoull(p, &p, 0);
>+		free(val);
>+		/* Move s to first partition */
>+		strsep(&s, ";");
>+	}
>+	if (s == NULL) {
>+		printf("Error: is the partitions string NULL-terminated?\n");
>+		return -EINVAL;
>+	}
>+
>+	/* remove the optional semicolon at the end of the string */
>+	i = strlen(s) - 1;
>+	if (s[i] == ';')
>+		s[i] = '\0';
>+
>+	/* calculate expected number of partitions */
>+	p_count = 1;
>+	p = s;
>+	while (*p) {
>+		if (*p++ == ';')
>+			p_count++;
>+	}
>+
>+	/* allocate memory for partitions */
>+	parts = calloc(sizeof(struct disk_partition), p_count);
>+	if (parts == NULL)
>+		return -ENOMEM;
>+
>+	/* retrieve partitions data from string */
>+	for (i = 0; i < p_count; i++) {
>+		tok = strsep(&s, ";");
>+
>+		if (tok == NULL)
>+			break;
>+
>+		/* size */
>+		val = extract_val(tok, "size");
>+		if (!val) { /* 'size' is mandatory */
>+			errno = -4;
>+			goto err;
>+		}
>+		p = val;
>+		if ((strcmp(p, "-") == 0)) {
>+			/* auto extend the size */
>+			parts[i].size = 0;
>+		} else {
>+			size_ll = ustrtoull(p, &p, 0);
>+			parts[i].size = size_ll / 512;

The sector size may have other values than 512.


>+		}
>+		free(val);
>+
>+		/* start address */
>+		val = extract_val(tok, "start");
>+		if (val) { /* start address is optional */
>+			p = val;
>+			start_ll = ustrtoull(p, &p, 0);
>+			parts[i].start = start_ll / 512;

Same here.

Best regards

Heinrich


>+			free(val);
>+		}
>+
>+		/* system id */
>+		val = extract_val(tok, "id");
>+		if (!val) { /* '' is mandatory */
>+			errno = -4;
>+			goto err;
>+		}
>+		p = val;
>+		parts[i].sys_ind = ustrtoul(p, &p, 0);
>+		free(val);
>+
>+		/* bootable */
>+		if (found_key(tok, "bootable"))
>+			parts[i].bootable = PART_BOOTABLE;
>+	}
>+
>+	*parts_count = p_count;
>+	*partitions = parts;
>+	free(str);
>+
>+	return 0;
>+err:
>+	free(str);
>+	free(parts);
>+
>+	return errno;
>+}
>+
>+static int do_write_mbr(struct blk_desc *dev, const char *str)
>+{
>+	unsigned long disk_uuid = 0;
>+	struct disk_partition *partitions;
>+	int count;
>+
>+	if (str_to_partition_info(str, &disk_uuid, &partitions, &count)) {
>+		printf("MBR: failed to setup partitions from \"%s\"\n", str);
>+		return -1;
>+	}
>+
>+	if (layout_mbr_partitions(partitions, count, dev->lba)) {
>+		printf("MBR: failed to layout partitions on the device\n");
>+		free(partitions);
>+		return -1;
>+	}
>+
>+	if (write_mbr_partitions(dev, partitions, count, disk_uuid)) {
>+		printf("MBR: failed to write partitions to the device\n");
>+		free(partitions);
>+		return -1;
>+	}
>+
>+	return 0;
>+}
>+
>+static int do_verify_mbr(struct blk_desc *dev, const char *str)
>+{
>+	unsigned long disk_uuid = 0;
>+	struct disk_partition *partitions;
>+	int count, i, ret = 1;
>+
>+	if (str_to_partition_info(str, &disk_uuid, &partitions, &count)) {
>+		printf("MBR: failed to setup partitions from \"%s\"\n", str);
>+		return -1;
>+	}
>+
>+	for (i = 0; i < count; i++) {
>+		struct disk_partition p;
>+
>+		if (part_get_info(dev, i+1, &p))
>+			goto fail;
>+
>+		if ((partitions[i].size && p.size < partitions[i].size) ||
>+		    (partitions[i].start && p.start < partitions[i].start) ||
>+		    (p.sys_ind != partitions[i].sys_ind))
>+			goto fail;
>+	}
>+	ret = 0;
>+fail:
>+	free(partitions);
>+	return ret;
>+}
>+
>+static int do_mbr(struct cmd_tbl *cmdtp, int flag, int argc, char
>*const argv[])
>+{
>+	const char *parts = NULL;
>+	int ret = CMD_RET_SUCCESS;
>+	int dev = 0;
>+	char *ep;
>+	struct blk_desc *blk_dev_desc = NULL;
>+
>+	if (argc != 4 && argc != 5)
>+		return CMD_RET_USAGE;
>+
>+	dev = (int)simple_strtoul(argv[3], &ep, 10);
>+	if (!ep || ep[0] != '\0') {
>+		printf("'%s' is not a number\n", argv[3]);
>+		return CMD_RET_USAGE;
>+	}
>+	blk_dev_desc = blk_get_dev(argv[2], dev);
>+	if (!blk_dev_desc) {
>+		printf("%s: %s dev %d NOT available\n",
>+		       __func__, argv[2], dev);
>+		return CMD_RET_FAILURE;
>+	}
>+
>+	if ((strcmp(argv[1], "write") == 0)) {
>+		parts = (argc == 5) ? argv[4] : env_get("mbr_parts");
>+		printf("MBR: write ");
>+		ret = do_write_mbr(blk_dev_desc, parts);
>+	} else if ((strcmp(argv[1], "verify") == 0)) {
>+		printf("MBR: verify ");
>+		parts = (argc == 5) ? argv[4] : env_get("mbr_parts");
>+		ret = do_verify_mbr(blk_dev_desc, parts);
>+	} else {
>+		return CMD_RET_USAGE;
>+	}
>+
>+	if (ret) {
>+		printf("error!\n");
>+		return CMD_RET_FAILURE;
>+	}
>+
>+	printf("success!\n");
>+	return CMD_RET_SUCCESS;
>+}
>+
>+U_BOOT_CMD(mbr, CONFIG_SYS_MAXARGS, 1, do_mbr,
>+	"MBR (Master Boot Record)",
>+	"<command> <interface> <dev> <partitions_list>\n"
>+	" - MBR partition table restoration utility\n"
>+	" Restore or check partition information on a device connected\n"
>+	" to the given block interface\n"
>+	" Example usage:\n"
>+	" mbr write mmc 0 [\"${mbr_parts}\"]\n"
>+	" mbr verify mmc 0 [\"${partitions}\"]\n"
>+);