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Merge branch 'work.cramfs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 

Pull cramfs updates from Al Viro:
 "Nicolas Pitre's cramfs work"

* 'work.cramfs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  cramfs: rehabilitate it
  cramfs: add mmap support
  cramfs: implement uncompressed and arbitrary data block positioning
  cramfs: direct memory access support
This commit is contained in:
Linus Torvalds 2017-11-17 13:20:41 -08:00
parent ca5b857cb0 8d59598c35
commit cbda1b270f
6 changed files with 586 additions and 71 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
Documentation/filesystems/cramfs.txt
View File

@ -45,6 +45,48 @@ you can just change the #define in mkcramfs.c, so long as you don't
mind the filesystem becoming unreadable to future kernels.
Memory Mapped cramfs image
--------------------------
The CRAMFS_MTD Kconfig option adds support for loading data directly from
a physical linear memory range (usually non volatile memory like Flash)
instead of going through the block device layer. This saves some memory
since no intermediate buffering is necessary to hold the data before
decompressing.
And when data blocks are kept uncompressed and properly aligned, they will
automatically be mapped directly into user space whenever possible providing
eXecute-In-Place (XIP) from ROM of read-only segments. Data segments mapped
read-write (hence they have to be copied to RAM) may still be compressed in
the cramfs image in the same file along with non compressed read-only
segments. Both MMU and no-MMU systems are supported. This is particularly
handy for tiny embedded systems with very tight memory constraints.
The location of the cramfs image in memory is system dependent. You must
know the proper physical address where the cramfs image is located and
configure an MTD device for it. Also, that MTD device must be supported
by a map driver that implements the "point" method. Examples of such
MTD drivers are cfi_cmdset_0001 (Intel/Sharp CFI flash) or physmap
(Flash device in physical memory map). MTD partitions based on such devices
are fine too. Then that device should be specified with the "mtd:" prefix
as the mount device argument. For example, to mount the MTD device named
"fs_partition" on the /mnt directory:
$ mount -t cramfs mtd:fs_partition /mnt
To boot a kernel with this as root filesystem, suffice to specify
something like "root=mtd:fs_partition" on the kernel command line.
Tools
-----
A version of mkcramfs that can take advantage of the latest capabilities
described above can be found here:
https://github.com/npitre/cramfs-tools
For /usr/share/magic
--------------------

4
MAINTAINERS
View File

@ -3720,8 +3720,8 @@ F: drivers/cpuidle/*
F: include/linux/cpuidle.h
CRAMFS FILESYSTEM
W: http://sourceforge.net/projects/cramfs/
S: Orphan / Obsolete
M: Nicolas Pitre <nico@linaro.org>
S: Maintained
F: Documentation/filesystems/cramfs.txt
F: fs/cramfs/

39
fs/cramfs/Kconfig
View File

@ -1,6 +1,5 @@
config CRAMFS
tristate "Compressed ROM file system support (cramfs) (OBSOLETE)"
depends on BLOCK
tristate "Compressed ROM file system support (cramfs)"
select ZLIB_INFLATE
help
Saying Y here includes support for CramFs (Compressed ROM File
@ -16,7 +15,39 @@ config CRAMFS
cramfs. Note that the root file system (the one containing the
directory /) cannot be compiled as a module.
This filesystem is obsoleted by SquashFS, which is much better
in terms of performance and features.
This filesystem is limited in capabilities and performance on
purpose to remain small and low on RAM usage. It is most suitable
for small embedded systems. If you have ample RAM to spare, you may
consider a more capable compressed filesystem such as SquashFS
which is much better in terms of performance and features.
If unsure, say N.
config CRAMFS_BLOCKDEV
bool "Support CramFs image over a regular block device" if EXPERT
depends on CRAMFS && BLOCK
default y
help
This option allows the CramFs driver to load data from a regular
block device such a disk partition or a ramdisk.
config CRAMFS_MTD
bool "Support CramFs image directly mapped in physical memory"
depends on CRAMFS && MTD
default y if !CRAMFS_BLOCKDEV
help
This option allows the CramFs driver to load data directly from
a linear adressed memory range (usually non volatile memory
like flash) instead of going through the block device layer.
This saves some memory since no intermediate buffering is
necessary.
The location of the CramFs image is determined by a
MTD device capable of direct memory mapping e.g. from
the 'physmap' map driver or a resulting MTD partition.
For example, this would mount the cramfs image stored in
the MTD partition named "xip_fs" on the /mnt mountpoint:
mount -t cramfs mtd:xip_fs /mnt
If unsure, say N.

31
fs/cramfs/README
View File

@ -49,17 +49,46 @@ same as the start of the (i+1)'th <block> if there is one). The first
<block> immediately follows the last <block_pointer> for the file.
<block_pointer>s are each 32 bits long.
When the CRAMFS_FLAG_EXT_BLOCK_POINTERS capability bit is set, each
<block_pointer>'s top bits may contain special flags as follows:
CRAMFS_BLK_FLAG_UNCOMPRESSED (bit 31):
The block data is not compressed and should be copied verbatim.
CRAMFS_BLK_FLAG_DIRECT_PTR (bit 30):
The <block_pointer> stores the actual block start offset and not
its end, shifted right by 2 bits. The block must therefore be
aligned to a 4-byte boundary. The block size is either blksize
if CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified, otherwise
the compressed data length is included in the first 2 bytes of
the block data. This is used to allow discontiguous data layout
and specific data block alignments e.g. for XIP applications.
The order of <file_data>'s is a depth-first descent of the directory
tree, i.e. the same order as `find -size +0 \( -type f -o -type l \)
-print'.
<block>: The i'th <block> is the output of zlib's compress function
applied to the i'th blksize-sized chunk of the input data.
applied to the i'th blksize-sized chunk of the input data if the
corresponding CRAMFS_BLK_FLAG_UNCOMPRESSED <block_ptr> bit is not set,
otherwise it is the input data directly.
(For the last <block> of the file, the input may of course be smaller.)
Each <block> may be a different size. (See <block_pointer> above.)
<block>s are merely byte-aligned, not generally u32-aligned.
When CRAMFS_BLK_FLAG_DIRECT_PTR is specified then the corresponding
<block> may be located anywhere and not necessarily contiguous with
the previous/next blocks. In that case it is minimally u32-aligned.
If CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified then the size is always
blksize except for the last block which is limited by the file length.
If CRAMFS_BLK_FLAG_DIRECT_PTR is set and CRAMFS_BLK_FLAG_UNCOMPRESSED
is not set then the first 2 bytes of the block contains the size of the
remaining block data as this cannot be determined from the placement of
logically adjacent blocks.
Holes
-----

515
fs/cramfs/inode.c
View File

@ -15,10 +15,15 @@
#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>
@ -36,6 +41,9 @@ struct cramfs_sb_info {
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)
@ -46,6 +54,7 @@ static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
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);
@ -93,6 +102,10 @@ static struct inode *get_cramfs_inode(struct super_block *sb,
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;
@ -140,6 +153,9 @@ static struct inode *get_cramfs_inode(struct super_block *sb,
* 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)]. */
@ -160,10 +176,10 @@ 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.
* Populate our block cache and return a pointer to it.
*/
static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
static void *cramfs_blkdev_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];
@ -239,11 +255,250 @@ static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned i
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: %s: last page is shared\n",
file_dentry(file)->d_name.name);
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_readpage().
*/
int i;
vma->vm_flags |= VM_MIXEDMAP;
for (i = 0; i < pages && !ret; i++) {
unsigned long off = i * PAGE_SIZE;
pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
ret = vm_insert_mixed(vma, vma->vm_start + off, pfn);
}
}
if (!ret)
pr_debug("mapped %s[%lu] at 0x%08lx (%u/%lu pages) "
"to vma 0x%08lx, page_prot 0x%llx\n",
file_dentry(file)->d_name.name, pgoff,
address, pages, vma_pages(vma), vma->vm_start,
(unsigned long long)pgprot_val(vma->vm_page_prot));
return ret;
bailout:
pr_debug("%s[%lu]: direct mmap impossible: %s\n",
file_dentry(file)->d_name.name, 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 vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 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 %s ofs %#lx siz %lu at 0x%08lx\n",
file_dentry(file)->d_name.name, 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 = generic_file_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);
kill_block_super(sb);
if (IS_ENABLED(CCONFIG_CRAMFS_MTD) && sb->s_mtd) {
if (sbi && sbi->mtd_point_size)
mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
kill_mtd_super(sb);
} else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
kill_block_super(sb);
}
kfree(sbi);
}
@ -254,34 +509,24 @@ static int cramfs_remount(struct super_block *sb, int *flags, char *data)
return 0;
}
static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
static int cramfs_read_super(struct super_block *sb,
struct cramfs_super *super, int silent)
{
int i;
struct cramfs_super super;
struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
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;
/* We don't know the real size yet */
sbi->size = PAGE_SIZE;
/* Read the first block and get the superblock from it */
memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
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) {
if (super->magic != CRAMFS_MAGIC) {
/* check for wrong endianness */
if (super.magic == CRAMFS_MAGIC_WEND) {
if (super->magic == CRAMFS_MAGIC_WEND) {
if (!silent)
pr_err("wrong endianness\n");
return -EINVAL;
@ -289,10 +534,12 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
/* check at 512 byte offset */
mutex_lock(&read_mutex);
memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
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)
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");
@ -301,34 +548,34 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
}
/* get feature flags first */
if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
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)) {
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);
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;
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;
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) &&
else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
((root_offset != sizeof(struct cramfs_super)) &&
(root_offset != 512 + sizeof(struct cramfs_super))))
{
@ -336,9 +583,18 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
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 |= MS_RDONLY;
sb->s_op = &cramfs_ops;
root = get_cramfs_inode(sb, &super.root, 0);
root = get_cramfs_inode(sb, cramfs_root, 0);
if (IS_ERR(root))
return PTR_ERR(root);
sb->s_root = d_make_root(root);
@ -347,10 +603,79 @@ static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
return 0;
}
static int cramfs_blkdev_fill_super(struct super_block *sb, void *data,
int silent)
{
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, &super, silent);
if (err)
return err;
return cramfs_finalize_super(sb, &super.root);
}
static int cramfs_mtd_fill_super(struct super_block *sb, void *data,
int silent)
{
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, &super, silent);
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 = huge_encode_dev(sb->s_bdev->bd_dev);
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;
@ -502,34 +827,86 @@ static int cramfs_readpage(struct file *file, struct page *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;
u32 blkptr_offset = OFFSET(inode) + page->index * 4;
u32 block_ptr, block_start, block_len;
bool uncompressed, direct;
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);
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 (compr_len == 0)
; /* hole */
else if (unlikely(compr_len > (PAGE_SIZE << 1))) {
pr_err("bad compressed blocksize %u\n",
compr_len);
goto err;
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 (page->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 (page->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 {
mutex_lock(&read_mutex);
bytes_filled = cramfs_uncompress_block(pgdata,
PAGE_SIZE,
cramfs_read(sb, start_offset, compr_len),
compr_len);
mutex_unlock(&read_mutex);
if (unlikely(bytes_filled < 0))
goto err;
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);
@ -573,10 +950,22 @@ static const struct super_operations cramfs_ops = {
.statfs = cramfs_statfs,
};
static struct dentry *cramfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
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);
struct dentry *ret = ERR_PTR(-ENOPROTOOPT);
if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
ret = mount_mtd(fs_type, flags, dev_name, data,
cramfs_mtd_fill_super);
if (!IS_ERR(ret))
return ret;
}
if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) {
ret = mount_bdev(fs_type, flags, dev_name, data,
cramfs_blkdev_fill_super);
}
return ret;
}
static struct file_system_type cramfs_fs_type = {

26
include/uapi/linux/cramfs_fs.h
View File

@ -74,6 +74,7 @@ struct cramfs_super {
#define CRAMFS_FLAG_HOLES 0x00000100 /* support for holes */
#define CRAMFS_FLAG_WRONG_SIGNATURE 0x00000200 /* reserved */
#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400 /* shifted root fs */
#define CRAMFS_FLAG_EXT_BLOCK_POINTERS 0x00000800 /* block pointer extensions */
/*
* Valid values in super.flags. Currently we refuse to mount
@ -83,7 +84,30 @@ struct cramfs_super {
#define CRAMFS_SUPPORTED_FLAGS ( 0x000000ff \
| CRAMFS_FLAG_HOLES \
| CRAMFS_FLAG_WRONG_SIGNATURE \
| CRAMFS_FLAG_SHIFTED_ROOT_OFFSET )
| CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \
| CRAMFS_FLAG_EXT_BLOCK_POINTERS )
/*
* Block pointer flags
*
* The maximum block offset that needs to be represented is roughly:
*
* (1 << CRAMFS_OFFSET_WIDTH) * 4 +
* (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE)
* = 0x11004000
*
* That leaves room for 3 flag bits in the block pointer table.
*/
#define CRAMFS_BLK_FLAG_UNCOMPRESSED (1 << 31)
#define CRAMFS_BLK_FLAG_DIRECT_PTR (1 << 30)
#define CRAMFS_BLK_FLAGS ( CRAMFS_BLK_FLAG_UNCOMPRESSED \
| CRAMFS_BLK_FLAG_DIRECT_PTR )
/*
* Direct blocks are at least 4-byte aligned.
* Pointers to direct blocks are shifted down by 2 bits.
*/
#define CRAMFS_BLK_DIRECT_PTR_SHIFT 2
#endif /* _UAPI__CRAMFS_H */