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SubjectRe: Compatibility issue with 2.2.19pre7
Date
Zitiere Russell King <rmk@arm.linux.org.uk>:
> The API changed:
> struct nfs_mount_data {
> int version; /* 1 */
> int fd; /* 1 */
> - struct nfs_fh root; /* 1 */
> + struct nfs2_fh old_root; /* 1 */

I don't see an API change:
the 2.2.17 "struct nfs_fs" and the 2.2.18 "struct nfs2_fh" are identical.

Ok, I see the problem:

struct nfs_fh {
unsigned short size;
unsigned char data[NFS_MAXFHSIZE];
}

The compiler thinks that data is a character array, thus no padding is inserted.
nlm_lookup_file casts f->data to "struct knfs_fs", a structure with pointers and
u32. --> unaligned u32 read --> boom.

Is that correct?
Is &(((struct nfs_fh*)0)->data) 2 or 4?

ARM isn't the only cpu that can't handle unaligned memory reads, why doesn't the
code fail on Alpha/Sparc? Does gcc insert padding on these cpus?


--
Manfred
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