From: Tom Rini <trini@konsulko.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [U-Boot, v2] fs: fat: fix reading non-cluster-aligned root directory
Date: Wed, 10 Apr 2019 08:20:19 -0400 [thread overview]
Message-ID: <20190410122019.GL4664@bill-the-cat> (raw)
In-Reply-To: <20190227105557.20908-1-anssi.hannula@bitwise.fi>
On Wed, Feb 27, 2019 at 12:55:57PM +0200, Anssi Hannula wrote:
> A FAT12/FAT16 root directory location is specified by a sector offset and
> it might not start at a cluster boundary. It also resides before the
> data area (before cluster 2).
>
> However, the current code assumes that the root directory is located at
> a beginning of a cluster, causing no files to be found if that is not
> the case.
>
> Since the FAT12/FAT16 root directory is located before the data area
> and is not aligned to clusters, using unsigned cluster numbers to refer
> to the root directory does not work well (the "cluster number" may be
> negative, and even allowing it be signed would not make it properly
> aligned).
>
> Modify the code to not use the normal cluster numbering when referring to
> the root directory of FAT12/FAT16 and instead use a cluster-sized
> offsets counted from the root directory start sector.
>
> This is a relatively common case as at least the filesystem formatter on
> Win7 seems to create such filesystems by default on 2GB USB sticks when
> "FAT" is selected (cluster size 64 sectors, rootdir size 32 sectors,
> rootdir starts at half a cluster before cluster 2).
>
> dosfstools mkfs.vfat does not seem to create affected filesystems.
>
> Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
> Reviewed-by: Bernhard Messerklinger <bernhard.messerklinger@br-automation.com>
> Tested-by: Bernhard Messerklinger <bernhard.messerklinger@br-automation.com>
Applied to u-boot/master, thanks!
--
Tom
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prev parent reply other threads:[~2019-04-10 12:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-06 18:02 [U-Boot] [PATCH] fs: fat: fix reading non-cluster-aligned root directory Anssi Hannula
2018-11-08 12:19 ` [U-Boot] Antwort: " Bernhard Messerklinger
2019-02-27 10:55 ` [U-Boot] [PATCH v2] " Anssi Hannula
2019-03-25 5:38 ` [U-Boot] Antwort: " Bernhard Messerklinger
2019-04-10 12:20 ` Tom Rini [this message]
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