I have tried to fix up the endian-swapping patch for
the mkcramfs from sourceforge CVS, circa Mon Jun 24, 2002
:pserver:anonymous at cvs.cramfs.sourceforge.net:/cvsroot/cramfs
No guarantees, of course, use at your own risk.
Currently, I get as far as trying to start init with this
patch, (the same filesystem via NFS works fine.) This
may be due to the fact that I haven't touched the kernel
code, (that is, I have not allowed for ramdisk to handle
4k block size, as I've been led to believe I must.)
Here's what I'm seeing when I try to use my rootfs
(not that it's necessarily relevant, but I don't
want to imply that I know my patch is perfect):
RAMDISK: Compressed image found at block 0
Freeing initrd memory: 1270k freed
VFS: Mounted root (cramfs filesystem) readonly.
Freeing unused kernel memory: 196k init
Warning: unable to open an initial console.
Kernel panic: No init found. Try passing init= option to kernel.
<0>Rebooting in 180 seconds..
-- steve
And here's the patch:
diff -u -r1.1.1.1 mkcramfs.c
--- mkcramfs.c 24 Jun 2002 19:22:19 -0000 1.1.1.1
+++ mkcramfs.c 25 Jun 2002 15:56:42 -0000
@@ -95,6 +95,7 @@
static char *opt_name = NULL;
static int warn_dev, warn_gid, warn_namelen, warn_skip, warn_size, warn_uid;
+static int swap_endian = 0;
/* In-core version of inode / directory entry. */
struct entry {
@@ -130,6 +131,7 @@
" -i file insert a file image into the filesystem (requires
>= 2.4.0)\n"
" -n name set name of cramfs filesystem\n"
" -p pad by %d bytes for boot code\n"
+ " -r reverse endianness of filesystem\n"
" -s sort directory entries (old option, ignored)\n"
" -v be more verbose\n"
" -z make explicit holes (requires >= 2.3.39)\n"
@@ -372,6 +374,58 @@
return totalsize;
}
+#define wswap(x) (((x)>>24) | (((x)>>8)&0xff00) | \
+ (((x)&0xff00)<<8) | (((x)&0xff)<<24))
+
+/* routines to swap endianness/bitfields in inode/superblock block data */
+static void fix_inode(struct cramfs_inode *inode)
+{
+ if (!swap_endian) return;
+ inode->mode = (inode->mode >> 8) | ((inode->mode&0xff)<<8);
+ inode->uid = (inode->uid >> 8) | ((inode->uid&0xff)<<8);
+ inode->size = (inode->size >> 16) | (inode->size&0xff00) |
+ ((inode->size&0xff)<<16);
+ ((u32*)inode)[2] = wswap(inode->offset | (inode->namelen<<26));
+}
+
+static void fix_offset(struct cramfs_inode *inode, u32 offset)
+{
+ u32 tmp;
+ if (!swap_endian) return;
+ tmp = wswap(((u32*)inode)[2]);
+ ((u32*)inode)[2] = wswap((offset >> 2) | (tmp&0xfc000000));
+}
+
+static void fix_block_pointer(u32 *p)
+{
+ if (!swap_endian) return;
+ *p = wswap(*p);
+}
+
+static void fix_super(struct cramfs_super *super)
+{
+ u32 *p = (u32*)super;
+
+ if (!swap_endian) return;
+
+ /* fix superblock fields */
+ p[0] = wswap(p[0]); /* magic */
+ p[1] = wswap(p[1]); /* size */
+ p[2] = wswap(p[2]); /* flags */
+ p[3] = wswap(p[3]); /* future */
+
+ /* fix filesystem info fields */
+ p = (u32*)&super->fsid;
+ p[0] = wswap(p[0]); /* crc */
+ p[1] = wswap(p[1]); /* edition */
+ p[2] = wswap(p[2]); /* blocks */
+ p[3] = wswap(p[3]); /* files */
+
+ fix_inode(&super->root);
+}
+
+#undef wswap
+
/* Returns sizeof(struct cramfs_super), which includes the root inode. */
static unsigned int write_superblock(struct entry *root, char *base, int size)
{
@@ -405,7 +459,9 @@
super->root.uid = CRAMFS_16(root->uid);
super->root.gid = root->gid;
super->root.size = CRAMFS_24(root->size);
+ fix_super(super);
CRAMFS_SET_OFFSET(&(super->root), offset >> 2);
+ fix_offset(&(super->root), offset);
return offset;
}
@@ -421,6 +477,7 @@
die(MKFS_ERROR, 0, "filesystem too big");
}
CRAMFS_SET_OFFSET(inode, offset >> 2);
+ fix_offset(inode, offset);
}
/*
@@ -610,6 +667,7 @@
}
*(u32 *) (base + offset) = CRAMFS_32(curr);
+ fix_block_pointer((u32*)(base + offset));
offset += 4;
} while (size);
@@ -700,7 +758,7 @@
progname = argv[0];
/* command line options */
- while ((c = getopt(argc, argv, "hEe:i:n:psvz")) != EOF) {
+ while ((c = getopt(argc, argv, "hEe:i:n:prsvz")) != EOF) {
switch (c) {
case 'h':
usage(MKFS_OK);
@@ -727,6 +785,10 @@
case 'p':
opt_pad = PAD_SIZE;
fslen_ub += PAD_SIZE;
+ break;
+ case 'r':
+ swap_endian = 1;
+ fprintf(stderr, "Swapping filesystem endianness.\n");
break;
case 's':
/* old option, ignored */
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