/*
* 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/fs_context.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_set_mtime_to_ts(inode,
inode_set_atime_to_ts(inode, inode_set_ctime_to_ts(inode, 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 super_block *buffer_dev[READ_BUFFERS];
static int next_buffer;
/*
* Populate our block cache and return a pointer to it.
*/
static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
unsigned int len)
{
struct address_space *mapping = sb->s_bdev->bd_mapping;
struct file_ra_state ra = {};
struct page *pages[BLKS_PER_BUF];
unsigned i, blocknr, buffer;
unsigned long devsize;
char *data;
if (!len)
return NULL;
blocknr = offset >> PAGE_SHIFT;
offset &= PAGE_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_SHIFT;
blk_offset += offset;
if (blk_offset > BUFFER_SIZE ||
blk_offset + len > BUFFER_SIZE)
continue;
return read_buffers[i] + blk_offset;
}
devsize = bdev_nr_bytes(sb->s_bdev) >> PAGE_SHIFT;
/* Ok, read in BLKS_PER_BUF pages completely first. */
file_ra_state_init(&ra, mapping);
page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
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;
}
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_from_page(data, page, 0, PAGE_SIZE);
put_page(page);
} else
memset(data, 0, PAGE_SIZE);
data += PAGE_SIZE;
}
return read_buffers[buffer] + offset;
}
/*
* Return a pointer to the linearly addressed cramfs image in memory.
*/
static void *cramfs_direct_read(struct super_block *sb, unsigned int offset,
unsigned int len)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
if (!len)
return NULL;
if (len > sbi->size || offset > sbi->size - len)
return page_address(ZERO_PAGE(0));
return sbi->linear_virt_addr + offset;
}
/*
* 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 cramfs_sb_info *sbi = CRAMFS_SB(sb);
if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sbi->linear_virt_addr)
return cramfs_direct_read(sb, offset, len);
else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
return cramfs_blkdev_read(sb, offset, len);
else
return NULL;
}
/*
* For a mapping to be possible, we need a range of uncompressed and
* contiguous blocks. Return the offset for the first block and number of
* valid blocks for which that is true, or zero otherwise.
*/
static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
int i;
u32 *blockptrs, first_block_addr;
/*
* We can dereference memory directly here as this code may be
* reached only when there is a direct filesystem image mapping
* available in memory.
*/
blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff * 4);
first_block_addr = blockptrs[0] & ~CRAMFS_BLK_FLAGS;
i = 0;
do {
u32 block_off = i * (PAGE_SIZE >> CRAMFS_BLK_DIRECT_PTR_SHIFT);
u32 expect = (first_block_addr + block_off) |
CRAMFS_BLK_FLAG_DIRECT_PTR |
CRAMFS_BLK_FLAG_UNCOMPRESSED;
if (blockptrs[i] != expect) {
pr_debug("range: block %d/%d got %#x expects %#x\n",
pgoff+i, pgoff + *pages - 1,
blockptrs[i], expect);
if (i == 0)
return 0;
break;
}
} while (++i < *pages);
*pages = i;
return first_block_addr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
}
#ifdef CONFIG_MMU
/*
* Return true if the last page of a file in the filesystem image contains
* some other data that doesn't belong to that file. It is assumed that the
* last block is CRAMFS_BLK_FLAG_DIRECT_PTR | CRAMFS_BLK_FLAG_UNCOMPRESSED
* (verified by cramfs_get_block_range() and directly accessible in memory.
*/
static bool cramfs_last_page_is_shared(struct inode *inode)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
u32 partial, last_page, blockaddr, *blockptrs;
char *tail_data;
partial = offset_in_page(inode->i_size);
if (!partial)
return false;
last_page = inode->i_size >> PAGE_SHIFT;
blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode));
blockaddr = blockptrs[last_page] & ~CRAMFS_BLK_FLAGS;
blockaddr <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
tail_data = sbi->linear_virt_addr + blockaddr + partial;
return memchr_inv(tail_data, 0, PAGE_SIZE - partial) ? true : false;
}
static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
{
struct inode *inode = file_inode(file);
struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
unsigned int pages, max_pages, offset;
unsigned long address, pgoff = vma->vm_pgoff;
char *bailout_reason;
int ret;
ret = generic_file_readonly_mmap(file, vma);
if (ret)
return ret;
/*
* Now try to pre-populate ptes for this vma with a direct
* mapping avoiding memory allocation when possible.
*/
/* Could COW work here? */
bailout_reason = "vma is writable";
if (vma->vm_flags & VM_WRITE)
goto bailout;
max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
bailout_reason = "beyond file limit";
if (pgoff >= max_pages)
goto bailout;
pages = min(vma_pages(vma), max_pages - pgoff);
offset = cramfs_get_block_range(inode, pgoff, &pages);
bailout_reason = "unsuitable block layout";
if (!offset)
goto bailout;
address = sbi->linear_phys_addr + offset;
bailout_reason = "data is not page aligned";
if (!PAGE_ALIGNED(address))
goto bailout;
/* Don't map the last page if it contains some other data */
if (pgoff + pages == max_pages && cramfs_last_page_is_shared(inode)) {
pr_debug("mmap: %pD: last page is shared\n", file);
pages--;
}
if (!pages) {
bailout_reason = "no suitable block remaining";
goto bailout;
}
if (pages == vma_pages(vma)) {
/*
* The entire vma is mappable. remap_pfn_range() will
* make it distinguishable from a non-direct mapping
* in /proc/<pid>/maps by substituting the file offset
* with the actual physical address.
*/
ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
pages * PAGE_SIZE, vma->vm_page_prot);
} else {
/*
* Let's create a mixed map if we can't map it all.
* The normal paging machinery will take care of the
* unpopulated ptes via cramfs_read_folio().
*/
int i;
vm_flags_set(vma, VM_MIXEDMAP);
for (i = 0; i < pages && !ret; i++) {
vm_fault_t vmf;
unsigned long off = i * PAGE_SIZE;
pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
if (vmf & VM_FAULT_ERROR)
ret = vm_fault_to_errno(vmf, 0);
}
}
if (!ret)
pr_debug("mapped %pD[%lu] at 0x%08lx (%u/%lu pages) "
"to vma 0x%08lx, page_prot 0x%llx\n", file,
pgoff, address, pages, vma_pages(vma), vma->vm_start,
(unsigned long long)pgprot_val(vma->vm_page_prot));
return ret;
bailout:
pr_debug("%pD[%lu]: direct mmap impossible: %s\n",
file, pgoff, bailout_reason);
/* Didn't manage any direct map, but normal paging is still possible */
return 0;
}
#else /* CONFIG_MMU */
static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
{
return is_nommu_shared_mapping(vma->vm_flags) ? 0 : -ENOSYS;
}
static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
unsigned int pages, block_pages, max_pages, offset;
pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (pgoff >= max_pages || pages > max_pages - pgoff)
return -EINVAL;
block_pages = pages;
offset = cramfs_get_block_range(inode, pgoff, &block_pages);
if (!offset || block_pages != pages)
return -ENOSYS;
addr = sbi->linear_phys_addr + offset;
pr_debug("get_unmapped for %pD ofs %#lx siz %lu at 0x%08lx\n",
file, pgoff*PAGE_SIZE, len, addr);
return addr;
}
static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
{
return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
NOMMU_MAP_READ | NOMMU_MAP_EXEC;
}
#endif /* CONFIG_MMU */
static const struct file_operations cramfs_physmem_fops = {
.llseek = generic_file_llseek,
.read_iter = generic_file_read_iter,
.splice_read = filemap_splice_read,
.mmap = cramfs_physmem_mmap,
#ifndef CONFIG_MMU
.get_unmapped_area = cramfs_physmem_get_unmapped_area,
.mmap_capabilities = cramfs_physmem_mmap_capabilities,
#endif
};
static void cramfs_kill_sb(struct super_block *sb)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
generic_shutdown_super(sb);
if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sb->s_mtd) {
if (sbi && sbi->mtd_point_size)
mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
put_mtd_device(sb->s_mtd);
sb->s_mtd = NULL;
} else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
sync_blockdev(sb->s_bdev);
bdev_fput(sb->s_bdev_file);
}
kfree(sbi);
}
static int cramfs_reconfigure(struct fs_context *fc)
{
sync_filesystem(fc->root->d_sb);
fc->sb_flags |= SB_RDONLY;
return 0;
}
static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
struct cramfs_super *super)
{
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
unsigned long root_offset;
bool silent = fc->sb_flags & SB_SILENT;
/* We don't know the real size yet */
sbi->size = PAGE_SIZE;
/* Read the first block and get the superblock from it */
mutex_lock(&read_mutex);
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)
errorfc(fc, "wrong endianness");
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)
errorfc(fc, "wrong endianness");
else if (!silent)
errorfc(fc, "wrong magic");
return -EINVAL;
}
}
/* get feature flags first */
if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
errorfc(fc, "unsupported filesystem features");
return -EINVAL;
}
/* Check that the root inode is in a sane state */
if (!S_ISDIR(super->root.mode)) {
errorfc(fc, "root is not a directory");
return -EINVAL;
}
/* correct strange, hard-coded permissions of mkcramfs */
super->root.mode |= 0555;
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)
infofc(fc, "empty filesystem");
else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
((root_offset != sizeof(struct cramfs_super)) &&
(root_offset != 512 + sizeof(struct cramfs_super))))
{
errorfc(fc, "bad root offset %lu", root_offset);
return -EINVAL;
}
return 0;
}
static int cramfs_finalize_super(struct super_block *sb,
struct cramfs_inode *cramfs_root)
{
struct inode *root;
/* Set it all up.. */
sb->s_flags |= SB_RDONLY;
sb->s_time_min = 0;
sb->s_time_max = 0;
sb->s_op = &cramfs_ops;
root = get_cramfs_inode(sb, cramfs_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_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct cramfs_sb_info *sbi;
struct cramfs_super super;
int i, err;
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.. */
for (i = 0; i < READ_BUFFERS; i++)
buffer_blocknr[i] = -1;
err = cramfs_read_super(sb, fc, &super);
if (err)
return err;
return cramfs_finalize_super(sb, &super.root);
}
static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct cramfs_sb_info *sbi;
struct cramfs_super super;
int err;
sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
sb->s_fs_info = sbi;
/* Map only one page for now. Will remap it when fs size is known. */
err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
&sbi->linear_virt_addr, &sbi->linear_phys_addr);
if (err || sbi->mtd_point_size != PAGE_SIZE) {
pr_err("unable to get direct memory access to mtd:%s\n",
sb->s_mtd->name);
return err ? : -ENODATA;
}
pr_info("checking physical address %pap for linear cramfs image\n",
&sbi->linear_phys_addr);
err = cramfs_read_super(sb, fc, &super);
if (err)
return err;
/* Remap the whole filesystem now */
pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
sb->s_mtd->name, sbi->size/1024);
mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
&sbi->linear_virt_addr, &sbi->linear_phys_addr);
if (err || sbi->mtd_point_size != sbi->size) {
pr_err("unable to get direct memory access to mtd:%s\n",
sb->s_mtd->name);
return err ? : -ENODATA;
}
return cramfs_finalize_super(sb, &super.root);
}
static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *sb = dentry->d_sb;
u64 id = 0;
if (sb->s_bdev)
id = huge_encode_dev(sb->s_bdev->bd_dev);
else if (sb->s_dev)
id = huge_encode_dev(sb->s_dev);
buf->f_type = CRAMFS_MAGIC;
buf->f_bsize = PAGE_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 = u64_to_fsid(id);
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);
return d_splice_alias(inode, dentry);
}
static int cramfs_read_folio(struct file *file, struct folio *folio)
{
struct inode *inode = folio->mapping->host;
u32 maxblock;
int bytes_filled;
void *pgdata;
bool success = false;
maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
bytes_filled = 0;
pgdata = kmap_local_folio(folio, 0);
if (folio->index < maxblock) {
struct super_block *sb = inode->i_sb;
u32 blkptr_offset = OFFSET(inode) + folio->index * 4;
u32 block_ptr, block_start, block_len;
bool uncompressed, direct;
mutex_lock(&read_mutex);
block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
block_ptr &= ~CRAMFS_BLK_FLAGS;
if (direct) {
/*
* The block pointer is an absolute start pointer,
* shifted by 2 bits. The size is included in the
* first 2 bytes of the data block when compressed,
* or PAGE_SIZE otherwise.
*/
block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
if (uncompressed) {
block_len = PAGE_SIZE;
/* if last block: cap to file length */
if (folio->index == maxblock - 1)
block_len =
offset_in_page(inode->i_size);
} else {
block_len = *(u16 *)
cramfs_read(sb, block_start, 2);
block_start += 2;
}
} else {
/*
* The block pointer indicates one past the end of
* the current block (start of next block). If this
* is the first block then it starts where the block
* pointer table ends, otherwise its start comes
* from the previous block's pointer.
*/
block_start = OFFSET(inode) + maxblock * 4;
if (folio->index)
block_start = *(u32 *)
cramfs_read(sb, blkptr_offset - 4, 4);
/* Beware... previous ptr might be a direct ptr */
if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
/* See comments on earlier code. */
u32 prev_start = block_start;
block_start = prev_start & ~CRAMFS_BLK_FLAGS;
block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
block_start += PAGE_SIZE;
} else {
block_len = *(u16 *)
cramfs_read(sb, block_start, 2);
block_start += 2 + block_len;
}
}
block_start &= ~CRAMFS_BLK_FLAGS;
block_len = block_ptr - block_start;
}
if (block_len == 0)
; /* hole */
else if (unlikely(block_len > 2*PAGE_SIZE ||
(uncompressed && block_len > PAGE_SIZE))) {
mutex_unlock(&read_mutex);
pr_err("bad data blocksize %u\n", block_len);
goto err;
} else if (uncompressed) {
memcpy(pgdata,
cramfs_read(sb, block_start, block_len),
block_len);
bytes_filled = block_len;
} else {
bytes_filled = cramfs_uncompress_block(pgdata,
PAGE_SIZE,
cramfs_read(sb, block_start, block_len),
block_len);
}
mutex_unlock(&read_mutex);
if (unlikely(bytes_filled < 0))
goto err;
}
memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
flush_dcache_folio(folio);
success = true;
err:
kunmap_local(pgdata);
folio_end_read(folio, success);
return 0;
}
static const struct address_space_operations cramfs_aops = {
.read_folio = cramfs_read_folio
};
/*
* Our operations:
*/
/*
* A directory can only readdir
*/
static const struct file_operations cramfs_directory_operations = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.iterate_shared = cramfs_readdir,
};
static const struct inode_operations cramfs_dir_inode_operations = {
.lookup = cramfs_lookup,
};
static const struct super_operations cramfs_ops = {
.statfs = cramfs_statfs,
};
static int cramfs_get_tree(struct fs_context *fc)
{
int ret = -ENOPROTOOPT;
if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
if (!ret)
return 0;
}
if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
return ret;
}
static const struct fs_context_operations cramfs_context_ops = {
.get_tree = cramfs_get_tree,
.reconfigure = cramfs_reconfigure,
};
/*
* Set up the filesystem mount context.
*/
static int cramfs_init_fs_context(struct fs_context *fc)
{
fc->ops = &cramfs_context_ops;
return 0;
}
static struct file_system_type cramfs_fs_type = {
.owner = THIS_MODULE,
.name = "cramfs",
.init_fs_context = cramfs_init_fs_context,
.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_DESCRIPTION("Compressed ROM file system support");
MODULE_LICENSE("GPL");
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