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mkcramfs: option to swap endian #1

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mkcramfs: option to swap endian #1

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62 changes: 59 additions & 3 deletions mkcramfs.c
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Expand Up @@ -123,6 +123,7 @@ static int opt_xip = 0;
static int opt_xip_mmu = 0;
static char *opt_image = NULL;
static char *opt_name = NULL;
static int swap_endian = 0;

static int warn_dev, warn_gid, warn_namelen, warn_skip, warn_size, warn_uid;
static const char *const memory_exhausted = "memory exhausted";
Expand Down Expand Up @@ -161,6 +162,7 @@ static void __attribute__((noreturn)) usage(int status)
" -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 endian-ness of filesystem\n"
" -s sort directory entries (old option, ignored)\n"
" -v be more verbose\n"
" -x use extended block pointers (requires >= 4.15)\n"
Expand Down Expand Up @@ -512,6 +514,49 @@ static unsigned int parse_directory(struct entry *root_entry, const char *name,
return totalsize;
}

/* routines to swap endianness/bitfields in inode/superblock block data */
static void fix_inode(struct cramfs_inode *inode)
{
#define wswap(x) (((x)>>24) | (((x)>>8)&0xff00) | (((x)&0xff00)<<8) | (((x)&0xff)<<24))
/* attempt #2 */
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 = wswap(((u32*)inode)[2]);
((u32*)inode)[2] = wswap((offset >> 2) | (tmp&0xfc000000));
}

static void fix_block_pointer(u32 *p)
{
*p = wswap(*p);
}

static void fix_super(struct cramfs_super *super)
{
u32 *p = (u32*)super;

/* 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);
}

/* Returns sizeof(struct cramfs_super), which includes the root inode. */
static unsigned int write_superblock(struct entry *root, unsigned char *base,
int size)
Expand Down Expand Up @@ -546,6 +591,7 @@ static unsigned int write_superblock(struct entry *root, unsigned char *base,
super->root.gid = root->gid;
super->root.size = root->size;
super->root.offset = offset >> 2;
if (swap_endian) fix_super(super);

return offset;
}
Expand All @@ -560,7 +606,10 @@ static void set_data_offset(struct entry *entry, unsigned char *base, unsigned l
if (offset >= (1 << (2 + CRAMFS_OFFSET_WIDTH))) {
error_msg_and_die("filesystem too big");
}
inode->offset = (offset >> 2);
if (swap_endian)
fix_offset(inode, offset);
else
inode->offset = (offset >> 2);
}

/*
Expand Down Expand Up @@ -646,6 +695,7 @@ static unsigned int write_directory_structure(struct entry *entry,
stack_entries++;
}
entry = entry->next;
if (swap_endian) fix_inode(inode);
}

/*
Expand Down Expand Up @@ -859,6 +909,7 @@ static unsigned int write_blocks(unsigned char *base, unsigned int offset, struc
data += input;
size -= input;
*(u32 *) (base + offset) = blockptr_val;
if (swap_endian) fix_block_pointer((u32*)(base + offset));
offset += 4;
if (blockptr_val & CRAMFS_BLK_FLAGS)
super_flags |= CRAMFS_FLAG_EXT_BLOCK_POINTERS;
Expand Down Expand Up @@ -1273,7 +1324,7 @@ int main(int argc, char **argv)
progname = argv[0];

/* command line options */
while ((c = getopt(argc, argv, "hEe:i:n:psvxXzD:q")) != EOF) {
while ((c = getopt(argc, argv, "hEe:i:n:prsvxXzD:q")) != EOF) {
switch (c) {
case 'h':
usage(MKFS_OK);
Expand Down Expand Up @@ -1301,6 +1352,10 @@ int main(int argc, char **argv)
opt_pad = PAD_SIZE;
fslen_ub += PAD_SIZE;
break;
case 'r':
swap_endian = 1;
printf("Swapping filesystem endian-ness\n");
break;
case 's':
/* old option, ignored */
break;
Expand Down Expand Up @@ -1417,9 +1472,10 @@ int main(int argc, char **argv)
/* Put the checksum in. */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, (rom_image+opt_pad), (offset-opt_pad));
((struct cramfs_super *) (rom_image+opt_pad))->fsid.crc = crc;
if (opt_verbose)
printf("CRC: %x\n", crc);
if (swap_endian) crc = wswap(crc);
((struct cramfs_super *) (rom_image+opt_pad))->fsid.crc = crc;

/* Check to make sure we allocated enough space. */
if (fslen_ub < offset) {
Expand Down