[U-Boot] [PATCH v3 1/5] GPT: add accessor function for disk GUID

alison at peloton-tech.com
2017-06-03T02:22:30Z

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)
--
2.1.4