text: /*
   * 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.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/pagemap.h>
  #include <linux/init.h>
  #include <linux/string.h>
  #include <linux/blkdev.h>
  #include <linux/slab.h>
  #include <linux/vfs.h>
  #include <linux/mutex.h>
  #include <uapi/linux/cramfs_fs.h>
  #include <linux/uaccess.h>
  
  #include "internal.h"
  
  /*
   * cramfs super-block data in memory
   */
  struct cramfs_sb_info {
  	unsigned long magic;
  	unsigned long size;
  	unsigned long blocks;
  	unsigned long files;
  	unsigned long flags;
  };
  
  static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  {
  	return sb->s_fs_info;
  }
  
  static const struct super_operations cramfs_ops;
  static const struct inode_operations cramfs_dir_inode_operations;
  static const struct file_operations cramfs_directory_operations;
  static const struct address_space_operations cramfs_aops;
  
  static DEFINE_MUTEX(read_mutex);
  
  
  /* These macros may change in future, to provide better st_ino semantics. */
  #define OFFSET(x)	((x)->i_ino)
  
  static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  {
  	if (!cino->offset)
  		return offset + 1;
  	if (!cino->size)
  		return offset + 1;
  
  	/*
  	 * The file mode test fixes buggy mkcramfs implementations where
  	 * cramfs_inode->offset is set to a non zero value for entries
  	 * which did not contain data, like devices node and fifos.
  	 */
  	switch (cino->mode & S_IFMT) {
  	case S_IFREG:
  	case S_IFDIR:
  	case S_IFLNK:
  		return cino->offset << 2;
  	default:
  		break;
  	}
  	return offset + 1;
  }
  
  static struct inode *get_cramfs_inode(struct super_block *sb,
  	const struct cramfs_inode *cramfs_inode, unsigned int offset)
  {
  	struct inode *inode;
  	static struct timespec zerotime;
  
  	inode = iget_locked(sb, cramino(cramfs_inode, offset));
  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  	if (!(inode->i_state & I_NEW))
  		return inode;
  
  	switch (cramfs_inode->mode & S_IFMT) {
  	case S_IFREG:
  		inode->i_fop = &generic_ro_fops;
  		inode->i_data.a_ops = &cramfs_aops;
  		break;
  	case S_IFDIR:
  		inode->i_op = &cramfs_dir_inode_operations;
  		inode->i_fop = &cramfs_directory_operations;
  		break;
  	case S_IFLNK:
  		inode->i_op = &page_symlink_inode_operations;
  		inode->i_data.a_ops = &cramfs_aops;
  		break;
  	default:
  		init_special_inode(inode, cramfs_inode->mode,
  				old_decode_dev(cramfs_inode->size));
  	}
  
  	inode->i_mode = cramfs_inode->mode;
  	i_uid_write(inode, cramfs_inode->uid);
  	i_gid_write(inode, cramfs_inode->gid);
  
  	/* if the lower 2 bits are zero, the inode contains data */
  	if (!(inode->i_ino & 3)) {
  		inode->i_size = cramfs_inode->size;
  		inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
  	}
  
  	/* Struct copy intentional */
  	inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
  	/* 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. */
  
  	unlock_new_inode(inode);
  
  	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 address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
  	struct page *pages[BLKS_PER_BUF];
  	unsigned i, blocknr, buffer;
  	unsigned long devsize;
  	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 = mapping->host->i_size >> PAGE_CACHE_SHIFT;
  
  	/* Ok, read in BLKS_PER_BUF pages completely first. */
  	for (i = 0; i < BLKS_PER_BUF; i++) {
  		struct page *page = NULL;
  
  		if (blocknr + i < devsize) {
  			page = read_mapping_page(mapping, blocknr + i, NULL);
  			/* synchronous error? */
  			if (IS_ERR(page))
  				page = NULL;
  		}
  		pages[i] = page;
  	}
  
  	for (i = 0; i < BLKS_PER_BUF; i++) {
  		struct page *page = pages[i];
  
  		if (page) {
  			wait_on_page_locked(page);
  			if (!PageUptodate(page)) {
  				/* asynchronous error */
  				page_cache_release(page);
  				pages[i] = NULL;
  			}
  		}
  	}
  
  	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 page *page = pages[i];
  
  		if (page) {
  			memcpy(data, kmap(page), PAGE_CACHE_SIZE);
  			kunmap(page);
  			page_cache_release(page);
  		} else
  			memset(data, 0, PAGE_CACHE_SIZE);
  		data += PAGE_CACHE_SIZE;
  	}
  	return read_buffers[buffer] + offset;
  }
  
  static void cramfs_kill_sb(struct super_block *sb)
  {
  	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
  
  	kill_block_super(sb);
  	kfree(sbi);
  }
  
  static int cramfs_remount(struct super_block *sb, int *flags, char *data)
  {
  	sync_filesystem(sb);
  	*flags |= MS_RDONLY;
  	return 0;
  }
  
  static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
  {
  	int i;
  	struct cramfs_super super;
  	unsigned long root_offset;
  	struct cramfs_sb_info *sbi;
  	struct inode *root;
  
  	sb->s_flags |= MS_RDONLY;
  
  	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
  	if (!sbi)
  		return -ENOMEM;
  	sb->s_fs_info = sbi;
  
  	/* Invalidate the read buffers on mount: think disk change.. */
  	mutex_lock(&read_mutex);
  	for (i = 0; i < READ_BUFFERS; i++)
  		buffer_blocknr[i] = -1;
  
  	/* Read the first block and get the superblock from it */
  	memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
  	mutex_unlock(&read_mutex);
  
  	/* Do sanity checks on the superblock */
  	if (super.magic != CRAMFS_MAGIC) {
  		/* check for wrong endianness */
  		if (super.magic == CRAMFS_MAGIC_WEND) {
  			if (!silent)
  				pr_err("wrong endianness\n");
  			return -EINVAL;
  		}
  
  		/* 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 (super.magic == CRAMFS_MAGIC_WEND && !silent)
  				pr_err("wrong endianness\n");
  			else if (!silent)
  				pr_err("wrong magic\n");
  			return -EINVAL;
  		}
  	}
  
  	/* get feature flags first */
  	if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
  		pr_err("unsupported filesystem features\n");
  		return -EINVAL;
  	}
  
  	/* Check that the root inode is in a sane state */
  	if (!S_ISDIR(super.root.mode)) {
  		pr_err("root is not a directory\n");
  		return -EINVAL;
  	}
  	/* correct strange, hard-coded permissions of mkcramfs */
  	super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
  
  	root_offset = super.root.offset << 2;
  	if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
  		sbi->size = super.size;
  		sbi->blocks = super.fsid.blocks;
  		sbi->files = super.fsid.files;
  	} else {
  		sbi->size = 1<<28;
  		sbi->blocks = 0;
  		sbi->files = 0;
  	}
  	sbi->magic = super.magic;
  	sbi->flags = super.flags;
  	if (root_offset == 0)
  		pr_info("empty filesystem");
  	else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
  		 ((root_offset != sizeof(struct cramfs_super)) &&
  		  (root_offset != 512 + sizeof(struct cramfs_super))))
  	{
  		pr_err("bad root offset %lu\n", root_offset);
  		return -EINVAL;
  	}
  
  	/* Set it all up.. */
  	sb->s_op = &cramfs_ops;
  	root = get_cramfs_inode(sb, &super.root, 0);
  	if (IS_ERR(root))
  		return PTR_ERR(root);
  	sb->s_root = d_make_root(root);
  	if (!sb->s_root)
  		return -ENOMEM;
  	return 0;
  }
  
  static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
  {
  	struct super_block *sb = dentry->d_sb;
  	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
  
  	buf->f_type = CRAMFS_MAGIC;
  	buf->f_bsize = PAGE_CACHE_SIZE;
  	buf->f_blocks = CRAMFS_SB(sb)->blocks;
  	buf->f_bfree = 0;
  	buf->f_bavail = 0;
  	buf->f_files = CRAMFS_SB(sb)->files;
  	buf->f_ffree = 0;
  	buf->f_fsid.val[0] = (u32)id;
  	buf->f_fsid.val[1] = (u32)(id >> 32);
  	buf->f_namelen = CRAMFS_MAXPATHLEN;
  	return 0;
  }
  
  /*
   * Read a cramfs directory entry.
   */
  static int cramfs_readdir(struct file *file, struct dir_context *ctx)
  {
  	struct inode *inode = file_inode(file);
  	struct super_block *sb = inode->i_sb;
  	char *buf;
  	unsigned int offset;
  
  	/* Offset within the thing. */
  	if (ctx->pos >= inode->i_size)
  		return 0;
  	offset = ctx->pos;
  	/* Directory entries are always 4-byte aligned */
  	if (offset & 3)
  		return -EINVAL;
  
  	buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
  	if (!buf)
  		return -ENOMEM;
  
  	while (offset < inode->i_size) {
  		struct cramfs_inode *de;
  		unsigned long nextoffset;
  		char *name;
  		ino_t ino;
  		umode_t mode;
  		int namelen;
  
  		mutex_lock(&read_mutex);
  		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
  		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;
  		memcpy(buf, name, namelen);
  		ino = cramino(de, OFFSET(inode) + offset);
  		mode = de->mode;
  		mutex_unlock(&read_mutex);
  		nextoffset = offset + sizeof(*de) + namelen;
  		for (;;) {
  			if (!namelen) {
  				kfree(buf);
  				return -EIO;
  			}
  			if (buf[namelen-1])
  				break;
  			namelen--;
  		}
  		if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
  			break;
  
  		ctx->pos = offset = nextoffset;
  	}
  	kfree(buf);
  	return 0;
  }
  
  /*
   * Lookup and fill in the inode data..
   */
  static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
  {
  	unsigned int offset = 0;
  	struct inode *inode = NULL;
  	int sorted;
  
  	mutex_lock(&read_mutex);
  	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
  	while (offset < dir->i_size) {
  		struct cramfs_inode *de;
  		char *name;
  		int namelen, retval;
  		int dir_off = OFFSET(dir) + offset;
  
  		de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
  		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) {
  				inode = ERR_PTR(-EIO);
  				goto out;
  			}
  			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) {
  			inode = get_cramfs_inode(dir->i_sb, de, dir_off);
  			break;
  		}
  		/* else (retval < 0) */
  		if (sorted)
  			break;
  	}
  out:
  	mutex_unlock(&read_mutex);
  	if (IS_ERR(inode))
  		return ERR_CAST(inode);
  	d_add(dentry, inode);
  	return NULL;
  }
  
  static int cramfs_readpage(struct file *file, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	u32 maxblock;
  	int bytes_filled;
  	void *pgdata;
  
  	maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  	bytes_filled = 0;
  	pgdata = kmap(page);
  
  	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;
  		mutex_lock(&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);
  		mutex_unlock(&read_mutex);
  
  		if (compr_len == 0)
  			; /* hole */
  		else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
  			pr_err("bad compressed blocksize %u\n",
  				compr_len);
  			goto err;
  		} else {
  			mutex_lock(&read_mutex);
  			bytes_filled = cramfs_uncompress_block(pgdata,
  				 PAGE_CACHE_SIZE,
  				 cramfs_read(sb, start_offset, compr_len),
  				 compr_len);
  			mutex_unlock(&read_mutex);
  			if (unlikely(bytes_filled < 0))
  				goto err;
  		}
  	}
  
  	memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
  	flush_dcache_page(page);
  	kunmap(page);
  	SetPageUptodate(page);
  	unlock_page(page);
  	return 0;
  
  err:
  	kunmap(page);
  	ClearPageUptodate(page);
  	SetPageError(page);
  	unlock_page(page);
  	return 0;
  }
  
  static const struct address_space_operations cramfs_aops = {
  	.readpage = cramfs_readpage
  };
  
  /*
   * Our operations:
   */
  
  /*
   * A directory can only readdir
   */
  static const struct file_operations cramfs_directory_operations = {
  	.llseek		= generic_file_llseek,
  	.read		= generic_read_dir,
  	.iterate	= cramfs_readdir,
  };
  
  static const struct inode_operations cramfs_dir_inode_operations = {
  	.lookup		= cramfs_lookup,
  };
  
  static const struct super_operations cramfs_ops = {
  	.remount_fs	= cramfs_remount,
  	.statfs		= cramfs_statfs,
  };
  
  static struct dentry *cramfs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
  }
  
  static struct file_system_type cramfs_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "cramfs",
  	.mount		= cramfs_mount,
  	.kill_sb	= cramfs_kill_sb,
  	.fs_flags	= FS_REQUIRES_DEV,
  };
  MODULE_ALIAS_FS("cramfs");
  
  static int __init init_cramfs_fs(void)
  {
  	int rv;
  
  	rv = cramfs_uncompress_init();
  	if (rv < 0)
  		return rv;
  	rv = register_filesystem(&cramfs_fs_type);
  	if (rv < 0)
  		cramfs_uncompress_exit();
  	return rv;
  }
  
  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");
  