From: Alison Chaiken alison@peloton-tech.com
In order to read the GPT, modify the partition name strings, and then write out a new GPT, the disk GUID is needed. While there is an existing accessor for the partition UUIDs, there is none yet for the disk GUID.
Signed-off-by: Alison Chaiken alison@peloton-tech.com --- cmd/gpt.c | 26 ++++++++++++++++++++++++++ disk/part_efi.c | 31 +++++++++++++++++++++++++++++++ doc/README.gpt | 3 ++- include/part.h | 15 +++++++++++++++ 4 files changed, 74 insertions(+), 1 deletion(-)
diff --git a/cmd/gpt.c b/cmd/gpt.c index 3e98821..4d00a35 100644 --- a/cmd/gpt.c +++ b/cmd/gpt.c @@ -398,6 +398,23 @@ static int gpt_verify(struct blk_desc *blk_dev_desc, const char *str_part) return ret; }
+static int do_disk_guid(struct blk_desc *dev_desc, char * const namestr) +{ + int ret; + char disk_guid[UUID_STR_LEN + 1]; + + ret = get_disk_guid(dev_desc, disk_guid); + if (ret < 0) + return CMD_RET_FAILURE; + + if (namestr) + setenv(namestr, disk_guid); + else + printf("%s\n", disk_guid); + + return ret; +} + /** * do_gpt(): Perform GPT operations * @@ -436,6 +453,8 @@ static int do_gpt(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]) } else if ((strcmp(argv[1], "verify") == 0)) { ret = gpt_verify(blk_dev_desc, argv[4]); printf("Verify GPT: "); + } else if (strcmp(argv[1], "guid") == 0) { + return do_disk_guid(blk_dev_desc, argv[4]); } else { return CMD_RET_USAGE; } @@ -458,4 +477,11 @@ U_BOOT_CMD(gpt, CONFIG_SYS_MAXARGS, 1, do_gpt, " Example usage:\n" " gpt write mmc 0 $partitions\n" " gpt verify mmc 0 $partitions\n" + " guid <interface> <dev>\n" + " - print disk GUID\n" + " guid <interface> <dev> <varname>\n" + " - set environment variable to disk GUID\n" + " Example usage:\n" + " gpt guid mmc 0\n" + " gpt guid mmc 0 varname\n" ); diff --git a/disk/part_efi.c b/disk/part_efi.c index 20d33ef..71c3cb3 100644 --- a/disk/part_efi.c +++ b/disk/part_efi.c @@ -178,6 +178,37 @@ static void prepare_backup_gpt_header(gpt_header *gpt_h) * Public Functions (include/part.h) */
+/* + * UUID is displayed as 32 hexadecimal digits, in 5 groups, + * separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters + */ +int get_disk_guid(struct blk_desc * dev_desc, char *guid) +{ + ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_head, 1, dev_desc->blksz); + gpt_entry *gpt_pte = NULL; + unsigned char *guid_bin; + + /* This function validates AND fills in the GPT header and PTE */ + if (is_gpt_valid(dev_desc, GPT_PRIMARY_PARTITION_TABLE_LBA, + gpt_head, &gpt_pte) != 1) { + printf("%s: *** ERROR: Invalid GPT ***\n", __func__); + if (is_gpt_valid(dev_desc, dev_desc->lba - 1, + gpt_head, &gpt_pte) != 1) { + printf("%s: *** ERROR: Invalid Backup GPT ***\n", + __func__); + return -EINVAL; + } else { + printf("%s: *** Using Backup GPT ***\n", + __func__); + } + } + + guid_bin = gpt_head->disk_guid.b; + uuid_bin_to_str(guid_bin, guid, UUID_STR_FORMAT_GUID); + + return 0; +} + void part_print_efi(struct blk_desc *dev_desc) { ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_head, 1, dev_desc->blksz); diff --git a/doc/README.gpt b/doc/README.gpt index 3fcd835..c0779a4 100644 --- a/doc/README.gpt +++ b/doc/README.gpt @@ -171,7 +171,8 @@ To restore GUID partition table one needs to: The fields 'uuid' and 'uuid_disk' are optional if CONFIG_RANDOM_UUID is enabled. A random uuid will be used if omitted or they point to an empty/ non-existent environment variable. The environment variable will be set to - the generated UUID. + the generated UUID. The 'gpt guid' command reads the current value of the + uuid_disk from the GPT.
The field 'bootable' is optional, it is used to mark the GPT partition bootable (set attribute flags "Legacy BIOS bootable"). diff --git a/include/part.h b/include/part.h index 87b1111..16c4a46 100644 --- a/include/part.h +++ b/include/part.h @@ -371,6 +371,21 @@ int gpt_verify_headers(struct blk_desc *dev_desc, gpt_header *gpt_head, int gpt_verify_partitions(struct blk_desc *dev_desc, disk_partition_t *partitions, int parts, gpt_header *gpt_head, gpt_entry **gpt_pte); + + +/** + * get_disk_guid() - Function to read the GUID string from a device's GPT + * + * This function reads the GUID string from a block device whose descriptor + * is provided. + * + * @param dev_desc - block device descriptor + * @param guid - pre-allocated string in which to return the GUID + * + * @return - '0' on success, otherwise error + */ +int get_disk_guid(struct blk_desc *dev_desc, char *guid); + #endif
#if CONFIG_IS_ENABLED(DOS_PARTITION)