Re: [U-Boot] [PATCH 1/3] GPT: add accessor function for disk GUID

[Tom Rini]

On Sat, May 20, 2017 at 07:27:53PM -0700, ali...@peloton-tech.com wrote:

> From: Alison Chaiken 
> 
> 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 

Overall looks good, a few style things:

> + if (namestr != NULL)
> + setenv(namestr, disk_guid);

You can just if (namestr) here

[snip]
> + } else if (strcmp(argv[1], "guid") == 0) {
> + if (argc == 5) strcpy(varname, argv[4]);

Go ahead and do this on multiple lines please.  Thanks!

-- 
Tom


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[U-Boot] [PATCH 1/3] GPT: add accessor function for disk GUID

[alison]

From: Alison Chaiken 

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 
---
 cmd/gpt.c   | 29 -
 disk/part_efi.c | 31 +++
 include/part.h  | 15 +++
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/cmd/gpt.c b/cmd/gpt.c
index 3e98821..814cb11 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 != NULL)
+   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 +453,9 @@ 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 +478,11 @@ 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  \n"
+   "- print disk GUID\n"
+   " guid   \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 1b7ba27..de35c9b 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, _pte) != 1) {
+   printf("%s: *** ERROR: Invalid GPT ***\n", __func__);
+   if (is_gpt_valid(dev_desc, (dev_desc->lba - 1),
+gpt_head, _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/include/part.h b/include/part.h
index 83bce05..69143bb 100644
--- a/include/part.h
+++ b/include/part.h
@@ -367,6 +367,21 @@ 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

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