/*
* 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/file.h>
#include <linux/pagemap.h>
#include <linux/pfn_t.h>
#include <linux/ramfs.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/blkdev.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/super.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;
void *linear_virt_addr;
resource_size_t linear_phys_addr;
size_t mtd_point_size;
};
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 file_operations cramfs_physmem_fops;
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 timespec64 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;
if (IS_ENABLED(CONFIG_CRAMFS_MTD) &&
CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS &&
CRAMFS_SB(sb)->linear_phys_addr)
inode->i_fop = &cramfs_physmem_fops;
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_nohighmem(inode);
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_SIZE, so that the caller doesn't need to
* worry about end-of-buffer issues even when decompressing a full
* page cache.
*
* Note: This is all optimized away at compile time when
* CONFIG_CRAMFS_BLOCKDEV=n.
*/
#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_SIZE)
static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
static unsigned buffer_blocknr[READ_BUFFERS];
static struct