[U-Boot] [PATCH] fat: fix unaligned errors

Remy Bohmer
2009-01-02T09:32:39Z

Hello Mike,

2009/1/2 Mike Frysinger <vapier@gentoo.org>:
> From: Bryan Wu <bryan.wu@analog.com>
> A couple of buffers in the fat code are declared as an array of bytes. But
> it is then cast up to a structure with 16bit and 32bit members. Since GCC
> assumes structure alignment here, we have to force the buffers to be
> aligned according to the structure usage.

Just curious (because before the Christmas holidays I was also
debugging some FAT problems, and maybe this is related)
What problem/symptoms does this patch fix? How did the bug show itself?

Kind Regards,

Remy

>
> Signed-off-by: Bryan Wu <bryan.wu@analog.com>
> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
> ---
> fs/fat/fat.c | 19 +++++++++++++++----
> 1 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fat/fat.c b/fs/fat/fat.c
> index a9dde7d..06736d9 100644
> --- a/fs/fat/fat.c
> +++ b/fs/fat/fat.c
> @@ -429,12 +429,16 @@ slot2str(dir_slot *slotptr, char *l_name, int *idx)
>
>
> /*
> + * We need align this buffer to 16bit, cause it will be cast up to
> + * a dir_slot structure
> + */
> +__u8 get_vfatname_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u16))));
> +/*
> * Extract the full long filename starting at 'retdent' (which is really
> * a slot) into 'l_name'. If successful also copy the real directory entry
> * into 'retdent'
> * Return 0 on success, -1 otherwise.
> */
> -__u8 get_vfatname_block[MAX_CLUSTSIZE];
> static int
> get_vfatname(fsdata *mydata, int curclust, __u8 *cluster,
> dir_entry *retdent, char *l_name)
> @@ -517,10 +521,14 @@ mkcksum(const char *str)
>
>
> /*
> + * We need align this buffer to 32bit, cause it will be cast up to
> + * a dir_entry structure
> + */
> +__u8 get_dentfromdir_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u32))));
> +/*
> * Get the directory entry associated with 'filename' from the directory
> * starting at 'startsect'
> */
> -__u8 get_dentfromdir_block[MAX_CLUSTSIZE];
> static dir_entry *get_dentfromdir (fsdata * mydata, int startsect,
> char *filename, dir_entry * retdent,
> int dols)
> @@ -725,8 +733,11 @@ read_bootsectandvi(boot_sector *bs, volume_info *volinfo, int *fatsize)
> return -1;
> }
>
> -
> -__u8 do_fat_read_block[MAX_CLUSTSIZE]; /* Block buffer */
> +/*
> + * We need align this buffer to 32bit, cause it will be cast up to
> + * a dir_entry structure
> + */
> +__u8 do_fat_read_block[MAX_CLUSTSIZE] __attribute__ ((aligned(sizeof(__u32))));
> long
> do_fat_read (const char *filename, void *buffer, unsigned long maxsize,
> int dols)
> --
> 1.6.0.6
>
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