/* * Compressed rom filesystem for Linux. * * Copyright (C) 1999 Linus Torvalds. * * This file is released under the GPL. *//* * These are the VFS interfaces to the compressed rom filesystem. * The actual compression is based on zlib, see the other files. */#include <linux/module.h>#include <linux/fs.h>#include <linux/pagemap.h>#include <linux/init.h>#include <linux/string.h>#include <linux/locks.h>#include <linux/blkdev.h>#include <linux/cramfs_fs.h>#include <asm/semaphore.h>#include <asm/uaccess.h>#define CRAMFS_SB_MAGIC u.cramfs_sb.magic#define CRAMFS_SB_SIZE u.cramfs_sb.size#define CRAMFS_SB_BLOCKS u.cramfs_sb.blocks#define CRAMFS_SB_FILES u.cramfs_sb.files#define CRAMFS_SB_FLAGS u.cramfs_sb.flagsstatic struct super_operations cramfs_ops;static struct inode_operations cramfs_dir_inode_operations;static struct file_operations cramfs_directory_operations;static struct address_space_operations cramfs_aops;static DECLARE_MUTEX(read_mutex);/* These two macros may change in future, to provide better st_ino   semantics. */#define CRAMINO(x)	((x)->offset?(x)->offset<<2:1)#define OFFSET(x)	((x)->i_ino)static struct inode *get_cramfs_inode(struct super_block *sb, struct cramfs_inode * cramfs_inode){	struct inode * inode = new_inode(sb);	if (inode) {		inode->i_mode = cramfs_inode->mode;		inode->i_uid = cramfs_inode->uid;		inode->i_size = cramfs_inode->size;		inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;		inode->i_blksize = PAGE_CACHE_SIZE;		inode->i_gid = cramfs_inode->gid;		inode->i_ino = CRAMINO(cramfs_inode);		/* inode->i_nlink is left 1 - arguably wrong for directories,		   but it's the best we can do without reading the directory	           contents.  1 yields the right result in GNU find, even		   without -noleaf option. */		insert_inode_hash(inode);		if (S_ISREG(inode->i_mode)) {			inode->i_fop = &generic_ro_fops;			inode->i_data.a_ops = &cramfs_aops;		} else if (S_ISDIR(inode->i_mode)) {			inode->i_op = &cramfs_dir_inode_operations;			inode->i_fop = &cramfs_directory_operations;		} else if (S_ISLNK(inode->i_mode)) {			inode->i_op = &page_symlink_inode_operations;			inode->i_data.a_ops = &cramfs_aops;		} else {			inode->i_size = 0;			init_special_inode(inode, inode->i_mode, cramfs_inode->size);		}	}	return inode;}/* * We have our own block cache: don't fill up the buffer cache * with the rom-image, because the way the filesystem is set * up the accesses should be fairly regular and cached in the * page cache and dentry tree anyway.. * * This also acts as a way to guarantee contiguous areas of up to * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to * worry about end-of-buffer issues even when decompressing a full * page cache. */#define READ_BUFFERS (2)/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */#define NEXT_BUFFER(_ix) ((_ix) ^ 1)/* * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed" * data that takes up more space than the original and with unlucky * alignment. */#define BLKS_PER_BUF_SHIFT	(2)#define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)#define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_CACHE_SIZE)static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];static unsigned buffer_blocknr[READ_BUFFERS];static struct super_block * buffer_dev[READ_BUFFERS];static int next_buffer;/* * Returns a pointer to a buffer containing at least LEN bytes of * filesystem starting at byte offset OFFSET into the filesystem. */static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len){	struct buffer_head * bh_array[BLKS_PER_BUF];	struct buffer_head * read_array[BLKS_PER_BUF];	unsigned i, blocknr, buffer, unread;	unsigned long devsize;	int major, minor;	char *data;	if (!len)		return NULL;	blocknr = offset >> PAGE_CACHE_SHIFT;	offset &= PAGE_CACHE_SIZE - 1;	/* Check if an existing buffer already has the data.. */	for (i = 0; i < READ_BUFFERS; i++) {		unsigned int blk_offset;		if (buffer_dev[i] != sb)			continue;		if (blocknr < buffer_blocknr[i])			continue;		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;		blk_offset += offset;		if (blk_offset + len > BUFFER_SIZE)			continue;		return read_buffers[i] + blk_offset;	}	devsize = ~0UL;	major = MAJOR(sb->s_dev);	minor = MINOR(sb->s_dev);	if (blk_size[major])		devsize = blk_size[major][minor] >> 2;	/* Ok, read in BLKS_PER_BUF pages completely first. */	unread = 0;	for (i = 0; i < BLKS_PER_BUF; i++) {		struct buffer_head *bh;		bh = NULL;		if (blocknr + i < devsize) {			bh = sb_getblk(sb, blocknr + i);			if (!buffer_uptodate(bh))				read_array[unread++] = bh;		}		bh_array[i] = bh;	}	if (unread) {		ll_rw_block(READ, unread, read_array);		do {			unread--;			wait_on_buffer(read_array[unread]);		} while (unread);	}	/* Ok, copy them to the staging area without sleeping. */	buffer = next_buffer;	next_buffer = NEXT_BUFFER(buffer);	buffer_blocknr[buffer] = blocknr;	buffer_dev[buffer] = sb;	data = read_buffers[buffer];	for (i = 0; i < BLKS_PER_BUF; i++) {		struct buffer_head * bh = bh_array[i];		if (bh) {			memcpy(data, bh->b_data, PAGE_CACHE_SIZE);			brelse(bh);		} else			memset(data, 0, PAGE_CACHE_SIZE);		data += PAGE_CACHE_SIZE;	}	return read_buffers[buffer] + offset;}static struct super_block * cramfs_read_super(struct super_block *sb, void *data, int silent){	int i;	struct cramfs_super super;	unsigned long root_offset;	struct super_block * retval = NULL;	set_blocksize(sb->s_dev, PAGE_CACHE_SIZE);	sb->s_blocksize = PAGE_CACHE_SIZE;	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;	/* Invalidate the read buffers on mount: think disk change.. */	for (i = 0; i < READ_BUFFERS; i++)		buffer_blocknr[i] = -1;	down(&read_mutex);	/* Read the first block and get the superblock from it */	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));	up(&read_mutex);	//For debug, super.magic should be 0x28cd3d45, super.flag should be 0x3, Aaron	//printk("super.magic == 0x%x, super.flag == 0x%x\n", super.magic, super.flags);	/* Do sanity checks on the superblock */	if (super.magic != CRAMFS_MAGIC) {		/* check at 512 byte offset */		memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));		if (super.magic != CRAMFS_MAGIC) {			printk(KERN_ERR "cramfs: wrong magic\n");			goto out;		}	}	/* get feature flags first */	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {		printk(KERN_ERR "cramfs: unsupported filesystem features\n");		goto out;	}	/* Check that the root inode is in a sane state */	if (!S_ISDIR(super.root.mode)) {		printk(KERN_ERR "cramfs: root is not a directory\n");		goto out;	}	root_offset = super.root.offset << 2;	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {		sb->CRAMFS_SB_SIZE=super.size;		sb->CRAMFS_SB_BLOCKS=super.fsid.blocks;		sb->CRAMFS_SB_FILES=super.fsid.files;	} else {		sb->CRAMFS_SB_SIZE=1<<28;		sb->CRAMFS_SB_BLOCKS=0;		sb->CRAMFS_SB_FILES=0;	}	sb->CRAMFS_SB_MAGIC=super.magic;	sb->CRAMFS_SB_FLAGS=super.flags;	if (root_offset == 0)		printk(KERN_INFO "cramfs: empty filesystem");	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&		 ((root_offset != sizeof(struct cramfs_super)) &&		  (root_offset != 512 + sizeof(struct cramfs_super))))	{		printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);		goto out;	}	/* Set it all up.. */	sb->s_op = &cramfs_ops;	sb->s_root = d_alloc_root(get_cramfs_inode(sb, &super.root));	retval = sb;out:	return retval;}static int cramfs_statfs(struct super_block *sb, struct statfs *buf){	buf->f_type = CRAMFS_MAGIC;	buf->f_bsize = PAGE_CACHE_SIZE;	buf->f_blocks = sb->CRAMFS_SB_BLOCKS;	buf->f_bfree = 0;	buf->f_bavail = 0;	buf->f_files = sb->CRAMFS_SB_FILES;	buf->f_ffree = 0;	buf->f_namelen = CRAMFS_MAXPATHLEN;	return 0;}/* * Read a cramfs directory entry. */static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir){	struct inode *inode = filp->f_dentry->d_inode;	struct super_block *sb = inode->i_sb;	unsigned int offset;	int copied;	/* Offset within the thing. */	offset = filp->f_pos;	if (offset >= inode->i_size)		return 0;	/* Directory entries are always 4-byte aligned */	if (offset & 3)		return -EINVAL;	copied = 0;	while (offset < inode->i_size) {		struct cramfs_inode *de;		unsigned long nextoffset;		char *name;		int namelen, error;		down(&read_mutex);		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+256);		up(&read_mutex);		name = (char *)(de+1);		/*		 * Namelengths on disk are shifted by two		 * and the name padded out to 4-byte boundaries		 * with zeroes.		 */		namelen = de->namelen << 2;		nextoffset = offset + sizeof(*de) + namelen;		for (;;) {			if (!namelen)				return -EIO;			if (name[namelen-1])				break;			namelen--;		}		error = filldir(dirent, name, namelen, offset, CRAMINO(de), de->mode >> 12);		if (error)			break;		offset = nextoffset;		filp->f_pos = offset;		copied++;	}	return 0;}/* * Lookup and fill in the inode data.. */static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry){	unsigned int offset = 0;	int sorted = dir->i_sb->CRAMFS_SB_FLAGS & CRAMFS_FLAG_SORTED_DIRS;	while (offset < dir->i_size) {		struct cramfs_inode *de;		char *name;		int namelen, retval;		down(&read_mutex);		de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+256);		up(&read_mutex);		name = (char *)(de+1);		/* Try to take advantage of sorted directories */		if (sorted && (dentry->d_name.name[0] < name[0]))			break;		namelen = de->namelen << 2;		offset += sizeof(*de) + namelen;		/* Quick check that the name is roughly the right length */		if (((dentry->d_name.len + 3) & ~3) != namelen)			continue;		for (;;) {			if (!namelen)				return ERR_PTR(-EIO);			if (name[namelen-1])				break;			namelen--;		}		if (namelen != dentry->d_name.len)			continue;		retval = memcmp(dentry->d_name.name, name, namelen);		if (retval > 0)			continue;		if (!retval) {			d_add(dentry, get_cramfs_inode(dir->i_sb, de));			return NULL;		}		/* else (retval < 0) */		if (sorted)			break;	}	d_add(dentry, NULL);	return NULL;}static int cramfs_readpage(struct file *file, struct page * page){	struct inode *inode = page->mapping->host;	u32 maxblock, bytes_filled;	void *pgdata;	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;	bytes_filled = 0;	if (page->index < maxblock) {		struct super_block *sb = inode->i_sb;		u32 blkptr_offset = OFFSET(inode) + page->index*4;		u32 start_offset, compr_len;		start_offset = OFFSET(inode) + maxblock*4;		down(&read_mutex);		if (page->index)			start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);		compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);		up(&read_mutex);		pgdata = kmap(page);		if (compr_len == 0)			; /* hole */		else {			down(&read_mutex);			bytes_filled = cramfs_uncompress_block(pgdata,				 PAGE_CACHE_SIZE,				 cramfs_read(sb, start_offset, compr_len),				 compr_len);			up(&read_mutex);		}	} else		pgdata = kmap(page);	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);	kunmap(page);	flush_dcache_page(page);	SetPageUptodate(page);	UnlockPage(page);	return 0;}static struct address_space_operations cramfs_aops = {	readpage: cramfs_readpage};/* * Our operations: *//* * A directory can only readdir */static struct file_operations cramfs_directory_operations = {	read:		generic_read_dir,	readdir:	cramfs_readdir,};static struct inode_operations cramfs_dir_inode_operations = {	lookup:		cramfs_lookup,};static struct super_operations cramfs_ops = {	statfs:		cramfs_statfs,};static DECLARE_FSTYPE_DEV(cramfs_fs_type, "cramfs", cramfs_read_super);static int __init init_cramfs_fs(void){	cramfs_uncompress_init();	return register_filesystem(&cramfs_fs_type);}static void __exit exit_cramfs_fs(void){	cramfs_uncompress_exit();	unregister_filesystem(&cramfs_fs_type);}module_init(init_cramfs_fs)module_exit(exit_cramfs_fs)MODULE_LICENSE("GPL");