[U-Boot] [PATCH v2 3/6] GPT: add accessor function for disk GUID

Lukasz Majewski
2017-05-31T07:44:43Z

Hi Alison,

> From: Alison Chaiken <alison@she-devel.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.

Acked-by: Lukasz Majewski <lukma@denx.de>

>
> Signed-off-by: Alison Chaiken <alison@peloton-tech.com>
> ---
> cmd/gpt.c | 30 +++++++++++++++++++++++++++++-
> disk/part_efi.c | 31 +++++++++++++++++++++++++++++++
> doc/README.gpt | 3 ++-
> include/part.h | 15 +++++++++++++++
> 4 files changed, 77 insertions(+), 2 deletions(-)
>
> diff --git a/cmd/gpt.c b/cmd/gpt.c
> index 3e98821..3b7d929 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 1;
> +
> + if (namestr)
> + setenv(namestr, disk_guid);
> + else
> + printf("%s\n", disk_guid);
> +
> + return 0;
> +}
> +
> /**
> * do_gpt(): Perform GPT operations
> *
> @@ -412,7 +429,7 @@ static int do_gpt(cmd_tbl_t *cmdtp, int flag, int
> argc, char * const argv[]) {
> int ret = CMD_RET_SUCCESS;
> int dev = 0;
> - char *ep;
> + char *ep, *varname = NULL;
> struct blk_desc *blk_dev_desc = NULL;
>
> if (argc < 4 || argc > 5)
> @@ -436,6 +453,10 @@ 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) {
> + if (argc == 5)
> + strcpy(varname, argv[4]);
> + return do_disk_guid(blk_dev_desc, varname);
> } else {
> return CMD_RET_USAGE;
> }
> @@ -458,4 +479,11 @@ 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..ff9f408 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 -1;
> + } else {
> + printf("%s: *** Using Backup GPT
> ***\n",
> + __func__);
> + }
> + }
> +
> + guid_bin = (unsigned char *)(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)

Best regards,

Lukasz Majewski

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