linux-ext4 - Re: [PATCH] libblkid: support for GUID Partition Table (GPT), please?

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Date:	Sat, 15 May 2010 10:06:23 +0700
From:	Ivan Shmakov <ivan@...n.uusia.org>
To:	linux-ext4@...r.kernel.org
Cc:	Ivan Shmakov <oneingray@...il.com>
Subject: Re: [PATCH] libblkid: support for GUID Partition Table (GPT), please?

>>>>> "IS" == Ivan Shmakov <ivan@...n.uusia.org> writes:

 IS> GPT contains a supposed to be unique “Disk GUID” field, which
 IS> allows for the media bearing such a partition table to be
 IS> identified.

 IS> May I suggest adding support for GPT to libblkid?  An alpha-quality
 IS> patch is MIME'd.

	Ahem.  Wrong copy-paste late at night.  Should be better this
	time.

	For a test:

$ blkid -t TYPE=gpt /dev/sd? 
/dev/sdb: UUID="CE050C6F-E7BE-AD46-8FEE-F02476EC767E" TYPE="gpt" 
/dev/sdd: UUID="2A1210B5-535F-4A4A-84D0-34ABC6E57FFB" TYPE="gpt" 
/dev/sde: UUID="7B0FA8C6-26DD-1840-BBF5-46AD26CA551C" TYPE="gpt" 
/dev/sdf: UUID="04DF9DE5-CFDA-514D-99B7-CC61061FCE3C" TYPE="gpt" 
$ 

	Please note that the CRC-32 value contained in the GPT is not
	checked.

	The UUID could be printed in lower case instead.

-- 
FSF associate member #7257

diff --git a/lib/blkid/probe.c b/lib/blkid/probe.c
index 6b75732..8500320 100644
--- a/lib/blkid/probe.c
+++ b/lib/blkid/probe.c
@@ -1383,6 +1383,33 @@ static int probe_btrfs(struct blkid_probe *probe,
 	set_uuid(probe->dev, bs->fsid, 0);
 	return 0;
 }
+
+static int probe_gpt (struct blkid_probe *probe,
+                      struct blkid_magic *id,
+                      unsigned char *buf)
+{
+	struct gpt_header *gh
+		= (struct gpt_header *)(buf + 0x200);
+
+	/* FIXME: check gh->header_crc32 */
+
+	{
+		const __u8 *u = gh->disk_guid;
+		char uuid_str[33];
+
+		sprintf (uuid_str,
+			 ("%02X%02X%02X%02X"
+			  "-%02X%02X-%02X%02X-%02X%02X"
+			  "-%02X%02X%02X%02X%02X%02X"),
+			 u[0], u[1], u[2], u[3],
+			 u[4], u[5], u[6], u[7], u[8], u[9],
+			 u[10], u[11], u[12], u[13], u[14], u[15]);
+		blkid_set_tag (probe->dev, "UUID", uuid_str, 0);
+	}
+
+	return 0;
+}
+
 /*
  * Various filesystem magics that we can check for.  Note that kboff and
  * sboff are in kilobytes and bytes respectively.  All magics are in
@@ -1482,6 +1509,7 @@ static struct blkid_magic type_array[] = {
   { "lvm2pv",	 1,  0x018,  8, "LVM2 001",		probe_lvm2 },
   { "lvm2pv",	 1,  0x218,  8, "LVM2 001",		probe_lvm2 },
   { "btrfs",	 64,  0x40,  8, "_BHRfS_M",		probe_btrfs },
+  { "gpt",       0,  0x200,  8, "EFI PART",             probe_gpt },
   {   NULL,	 0,	 0,  0, NULL,			NULL }
 };
 
diff --git a/lib/blkid/probe.h b/lib/blkid/probe.h
index 37fc9c0..4d39b84 100644
--- a/lib/blkid/probe.h
+++ b/lib/blkid/probe.h
@@ -725,6 +725,28 @@ struct btrfs_super_block {
 	__u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
 } __attribute__ ((__packed__));
 
+struct gpt_header {
+	/* references:
+	 *   * linux/include/linux/efi.h;
+	 *   * Wikipedia entry.
+	 */
+	__u64 signature;
+	__u32 revision;
+	__u32 header_size;
+	__u32 header_crc32;
+	__u32 reserved1;
+	__u64 my_lba;
+	__u64 alternate_lba;
+	__u64 first_usable_lba;
+	__u64 last_usable_lba;
+	__u8 disk_guid[16];
+	__u64 partition_entry_lba;
+	__u32 num_partition_entries;
+	__u32 sizeof_partition_entry;
+	__u32 partition_entry_array_crc32;
+	__u8 reserved2[512 - 92];
+} __attribute__ ((__packed__));
+
 /*
  * Byte swap functions
  */


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