On Tue, 4 Dec 2007 13:01:26 +0100
Andi Drebes <lists-receive@xxxxxxxxxxxxxxxxxxx> wrote:
> The following patch makes cramfs little endian only. When trying to mount a big endian image,
> an error message is produced.
>
> The changes were tested on the following types of machines:
> An i386 compatible box (little endian)
> UltraSparc IIi (big endian)
>
> Signed-off-by: Andi Drebes <andi@xxxxxxxxxxxxxxxxxxx>
> ---
> inode.c | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 136 insertions(+), 27 deletions(-)
>
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 350680f..3fbf567 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c
> @@ -4,6 +4,10 @@
> * Copyright (C) 1999 Linus Torvalds.
> *
> * This file is released under the GPL.
> + *
> + * Changelog:
> + * 11/07 - Andi Drebes <andi@xxxxxxxxxxxxxxxxxxx>
> + * Made cramfs little endian only.
> */
>
> /*
> @@ -40,6 +44,95 @@ static DEFINE_MUTEX(read_mutex);
> #define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1)
> #define OFFSET(x) ((x)->i_ino)
>
> +#ifdef __BIG_ENDIAN
> +/* Converts a cramfs_info from little endian to big endian. */
> +static inline void cramfs_convert_info_letobe(struct cramfs_info* info)
> +{
> + info->crc = swab32(info->crc);
> + info->edition = swab32(info->edition);
> + info->blocks = swab32(info->blocks);
> + info->files = swab32(info->files);
> +}
> +
> +/* Converts a cramfs_info from little endian to big endian. */
> +static inline void cramfs_convert_inode_letobe(struct cramfs_inode* inode)
> +{
> + u8* inode_bytes = (u8*)inode;
> + u8 old_nloffs[4];
> +
> + inode->mode = swab16(inode->mode);
> + inode->uid = swab16(inode->uid);
> + inode->size = (inode_bytes[6] << 16) | (inode_bytes[5] << 8) | (inode_bytes[4]);
eww. Is there a nicer way of doing that?
Might be a bit tricky given the weird way in which struct cramfs_inode was
defined.
> +
> + /* Save the old values of the namelength and the offset */
> + memcpy(old_nloffs, inode_bytes+8, 4);
> +
> + /* Convert the namelength and the offset */
> + inode_bytes[8] = ((old_nloffs[0] & 0x3f) << 2) | ((old_nloffs[3] & 0xc0) >> 6);
> + inode_bytes[9] = ((old_nloffs[3] & 0x3f) << 2) | ((old_nloffs[2] & 0xc0) >> 6);
> + inode_bytes[10] = ((old_nloffs[2] & 0x3f) << 2) | ((old_nloffs[1] & 0xc0) >> 6);
> + inode_bytes[11] = ((old_nloffs[1] & 0x3f) << 2) | ((old_nloffs[0] & 0xc0) >> 6);
> +}
> +
> +/* Converts a cramfs superblock from little endian to big endian. */
> +static inline void cramfs_convert_super_letobe(struct cramfs_super* super)
> +{
> + super->magic = swab32(super->magic);
> + super->size = swab32(super->size);
> + super->flags = swab32(super->flags);
> + super->future = swab32(super->future);
> + cramfs_convert_info_letobe(&super->fsid);
> + cramfs_convert_inode_letobe(&super->root);
> +}
These inlines are not sane. Just removing those three takes the sparc64
fs/cramfs/inode.o from 6856 bytes of text down to 5668, which is rather a
large difference.
The patch has a number of trivial coding-style errors.
scripts/checkpatch.pl finds them.
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