path: root/block
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authorDavidlohr Bueso <davidlohr@hp.com>2013-09-13 15:02:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-15 07:10:16 -0400
commit6b02fa59a7cf34c548eedee657b07ea6c54d3894 (patch)
tree01279f3f74cbf1e1a2feadceb9ee37d4023fe82e /block
parent3711d86a2de17e967b576af8b8a1e9351a7d1466 (diff)
partitions/efi: loosen check fot pmbr size in lba
Matt found that commit 27a7c642174e ("partitions/efi: account for pmbr size in lba") caused his GPT formatted eMMC device not to boot. The reason is that this commit enforced Linux to always check the lesser of the whole disk or 2Tib for the pMBR size in LBA. While most disk partitioning tools out there create a pMBR with these characteristics, Microsoft does not, as it always sets the entry to the maximum 32-bit limitation - even though a drive may be smaller than that[1]. Loosen this check and only verify that the size is either the whole disk or 0xFFFFFFFF. No tool in its right mind would set it to any value other than these. [1] http://thestarman.pcministry.com/asm/mbr/GPT.htm#GPTPT Reported-and-tested-by: Matt Porter <matt.porter@linaro.org> Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block')
1 files changed, 6 insertions, 2 deletions
diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index 1a5ec9a03c00..1eb09ee5311b 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -186,6 +186,7 @@ invalid:
static int is_pmbr_valid(legacy_mbr *mbr, sector_t total_sectors)
+ uint32_t sz = 0;
int i, part = 0, ret = 0; /* invalid by default */
if (!mbr || le16_to_cpu(mbr->signature) != MSDOS_MBR_SIGNATURE)
@@ -216,12 +217,15 @@ check_hybrid:
* Protective MBRs take up the lesser of the whole disk
* or 2 TiB (32bit LBA), ignoring the rest of the disk.
+ * Some partitioning programs, nonetheless, choose to set
+ * the size to the maximum 32-bit limitation, disregarding
+ * the disk size.
* Hybrid MBRs do not necessarily comply with this.
if (ret == GPT_MBR_PROTECTIVE) {
- if (le32_to_cpu(mbr->partition_record[part].size_in_lba) !=
- min((uint32_t) total_sectors - 1, 0xFFFFFFFF))
+ sz = le32_to_cpu(mbr->partition_record[part].size_in_lba);
+ if (sz != (uint32_t) total_sectors - 1 && sz != 0xFFFFFFFF)
ret = 0;

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