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>

1 files changed, 9 insertions, 3 deletions

diff --git a/disk/part_dos.c b/disk/part_dos.c
index 7aff73d6f8..1a36be0446 100644
--- a/disk/part_dos.c
+++ b/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;
 }