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From: Ahmad Fatoum <>
Cc: Peter Rosin <>, Ahmad Fatoum <>
Subject: [PATCH master 1/5] fs: fat: pbl: support >32M alignment for first partition
Date: Wed, 22 Sep 2021 08:49:57 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

The LBA of the first absolute sector in a partition is a 32-bit
field at offset 0x8 of a partition entry. The first such partition
entry is at offset 446 of the MBR.

The DOS partition parser adheres to this scheme, but the FAT code
contains a very basic partition parser as well that kicks in when
a disk couldn't be mounted as FAT: It will seek to the first FAT
partition in a MBR and mount that. This only happens with FAT PBL,
because in barebox proper, we use the actual partition parser.

The partition parser in FAT assumed starting LBA to be a 16-bit
value and thus failed to load a first FAT partition located more
than 0x10000 sectors into the image. Fix this.

Signed-off-by: Ahmad Fatoum <>
 common/filetype.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/filetype.c b/common/filetype.c
index 9edebb2cd831..8ffcd6adcd09 100644
--- a/common/filetype.c
+++ b/common/filetype.c
@@ -218,7 +218,7 @@ enum filetype is_fat_or_mbr(const unsigned char *sector, unsigned long *bootsec)
 		 * first partition so we could check if there is a FAT boot
 		 * sector there
-		*bootsec = get_unaligned_le16(&sector[MBR_Table + MBR_StartSector]);
+		*bootsec = get_unaligned_le32(&sector[MBR_Table + MBR_StartSector]);
 	return filetype_mbr;

barebox mailing list

  reply	other threads:[~2021-09-22  6:59 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-22  6:49 [PATCH 0/5] ARM: at91: sama5d3_xplained: migrate to DT Ahmad Fatoum
2021-09-22  6:49 ` Ahmad Fatoum [this message]
2021-09-22  6:49 ` [PATCH master 2/5] ARM: at91: at91sam9263ek: add device tree check for board code Ahmad Fatoum
2021-09-22  6:49 ` [PATCH 3/5] Documentation: boards: at91: remove done TODOs Ahmad Fatoum
2021-09-22 15:29   ` Sam Ravnborg
2021-09-22  6:50 ` [PATCH 4/5] ARM: at91: sam9_smc: register driver earlier Ahmad Fatoum
2021-09-22  6:50 ` [PATCH 5/5] ARM: AT91: migrate sama5d3-xplained to DT Ahmad Fatoum
2021-10-01 13:36 ` [PATCH 0/5] ARM: at91: sama5d3_xplained: migrate " Sascha Hauer

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