part: extract MBR signature from partitions

EFI client programs need the signature information from the partition
table to determine the disk a partition is on, so we need to fill that
in here.

Signed-off-by: Peter Jones <pjones@redhat.com>
[separated from efi_loader part, and fixed build-errors for non-
 CONFIG_EFI_PARTITION case]
Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

disk/part_dos.c

@@ -89,14 +89,20 @@ static int test_block_type(unsigned char *buffer)
 
 static int part_test_dos(struct blk_desc *dev_desc)
 {
-	ALLOC_CACHE_ALIGN_BUFFER(unsigned char, buffer, dev_desc->blksz);
+	ALLOC_CACHE_ALIGN_BUFFER(legacy_mbr, mbr, dev_desc->blksz);
 
-	if (blk_dread(dev_desc, 0, 1, (ulong *)buffer) != 1)
+	if (blk_dread(dev_desc, 0, 1, (ulong *)mbr) != 1)
 		return -1;
 
-	if (test_block_type(buffer) != DOS_MBR)
+	if (test_block_type((unsigned char *)mbr) != DOS_MBR)
 		return -1;
 
+	if (dev_desc->sig_type == SIG_TYPE_NONE &&
+	    mbr->unique_mbr_signature != 0) {
+		dev_desc->sig_type = SIG_TYPE_MBR;
+		dev_desc->mbr_sig = mbr->unique_mbr_signature;
+	}
+
 	return 0;
 }
 

disk/part_efi.c

@@ -923,11 +923,19 @@ static int is_pmbr_valid(legacy_mbr * mbr)
 static int is_gpt_valid(struct blk_desc *dev_desc, u64 lba,
 			gpt_header *pgpt_head, gpt_entry **pgpt_pte)
 {
+	ALLOC_CACHE_ALIGN_BUFFER(legacy_mbr, mbr, dev_desc->blksz);
+
 	if (!dev_desc || !pgpt_head) {
 		printf("%s: Invalid Argument(s)\n", __func__);
 		return 0;
 	}
 
+	/* Read MBR Header from device */
+	if (blk_dread(dev_desc, 0, 1, (ulong *)mbr) != 1) {
+		printf("*** ERROR: Can't read MBR header ***\n");
+		return 0;
+	}
+
 	/* Read GPT Header from device */
 	if (blk_dread(dev_desc, (lbaint_t)lba, 1, pgpt_head) != 1) {
 		printf("*** ERROR: Can't read GPT header ***\n");
@@ -937,6 +945,18 @@ static int is_gpt_valid(struct blk_desc *dev_desc, u64 lba,
 	if (validate_gpt_header(pgpt_head, (lbaint_t)lba, dev_desc->lba))
 		return 0;
 
+	if (dev_desc->sig_type == SIG_TYPE_NONE) {
+		efi_guid_t empty = {};
+		if (memcmp(&pgpt_head->disk_guid, &empty, sizeof(empty))) {
+			dev_desc->sig_type = SIG_TYPE_GUID;
+			memcpy(&dev_desc->guid_sig, &pgpt_head->disk_guid,
+			      sizeof(empty));
+		} else if (mbr->unique_mbr_signature != 0) {
+			dev_desc->sig_type = SIG_TYPE_MBR;
+			dev_desc->mbr_sig = mbr->unique_mbr_signature;
+		}
+	}
+
 	/* Read and allocate Partition Table Entries */
 	*pgpt_pte = alloc_read_gpt_entries(dev_desc, pgpt_head);
 	if (*pgpt_pte == NULL) {

include/blk.h

@@ -8,6 +8,8 @@
 #ifndef BLK_H
 #define BLK_H
 
+#include <efi.h>
+
 #ifdef CONFIG_SYS_64BIT_LBA
 typedef uint64_t lbaint_t;
 #define LBAFlength "ll"
@@ -41,6 +43,17 @@ enum if_type {
 #define BLK_REV_SIZE		8
 
 /*
+ * Identifies the partition table type (ie. MBR vs GPT GUID) signature
+ */
+enum sig_type {
+	SIG_TYPE_NONE,
+	SIG_TYPE_MBR,
+	SIG_TYPE_GUID,
+
+	SIG_TYPE_COUNT			/* Number of signature types */
+};
+
+/*
  * With driver model (CONFIG_BLK) this is uclass platform data, accessible
  * with dev_get_uclass_platdata(dev)
  */
@@ -67,6 +80,11 @@ struct blk_desc {
 	char		vendor[BLK_VEN_SIZE + 1]; /* device vendor string */
 	char		product[BLK_PRD_SIZE + 1]; /* device product number */
 	char		revision[BLK_REV_SIZE + 1]; /* firmware revision */
+	enum sig_type	sig_type;	/* Partition table signature type */
+	union {
+		uint32_t mbr_sig;	/* MBR integer signature */
+		efi_guid_t guid_sig;	/* GPT GUID Signature */
+	};
 #if CONFIG_IS_ENABLED(BLK)
 	/*
 	 * For now we have a few functions which take struct blk_desc as a