cramfs: error message about endianess

The README file in the cramfs subdirectory says: "All data is currently in
host-endian format; neither mkcramfs nor the kernel ever do swabbing."

If somebody tries to mount a cramfs with the wrong endianess, cramfs only
complains about a wrong magic but doesn't inform the user that only the
endianess isn't right.

The following patch adds an error message to the cramfs sources.  If a user
tries to mount a cramfs with the wrong endianess using the patched sources,
cramfs will display the message "cramfs: wrong endianess".
Signed-off-by: NAndi Drebes <lists-receive@programmierforen.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/cramfs/inode.c

@@ -258,12 +258,21 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
 
 	/* Do sanity checks on the superblock */
 	if (super.magic != CRAMFS_MAGIC) {
+		/* check for wrong endianess */
+		if (super.magic == CRAMFS_MAGIC_WEND) {
+			if (!silent)
+				printk(KERN_ERR "cramfs: wrong endianess\n");
+			goto out;
+		}
+
 		/* check at 512 byte offset */
 		mutex_lock(&read_mutex);
 		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
 		mutex_unlock(&read_mutex);
 		if (super.magic != CRAMFS_MAGIC) {
-			if (!silent)
+			if (super.magic == CRAMFS_MAGIC_WEND && !silent)
+				printk(KERN_ERR "cramfs: wrong endianess\n");
+			else if (!silent)
 				printk(KERN_ERR "cramfs: wrong magic\n");
 			goto out;
 		}

include/linux/cramfs_fs.h

@@ -4,6 +4,7 @@
 #include <linux/types.h>
 
 #define CRAMFS_MAGIC		0x28cd3d45	/* some random number */
+#define CRAMFS_MAGIC_WEND	0x453dcd28	/* magic number with the wrong endianess */
 #define CRAMFS_SIGNATURE	"Compressed ROMFS"
 
 /*