1/*
   2 * Compressed rom filesystem for Linux.
   3 *
   4 * Copyright (C) 1999 Linus Torvalds.
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9/*
  10 * These are the VFS interfaces to the compressed rom filesystem.
  11 * The actual compression is based on zlib, see the other files.
  12 */
  13
  14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16#include <linux/module.h>
  17#include <linux/fs.h>
  18#include <linux/file.h>
  19#include <linux/pagemap.h>
  20#include <linux/pfn_t.h>
  21#include <linux/ramfs.h>
  22#include <linux/init.h>
  23#include <linux/string.h>
  24#include <linux/blkdev.h>
  25#include <linux/mtd/mtd.h>
  26#include <linux/mtd/super.h>
  27#include <linux/fs_context.h>
  28#include <linux/slab.h>
  29#include <linux/vfs.h>
  30#include <linux/mutex.h>
  31#include <uapi/linux/cramfs_fs.h>
  32#include <linux/uaccess.h>
  33
  34#include "internal.h"
  35
  36/*
  37 * cramfs super-block data in memory
  38 */
  39struct cramfs_sb_info {
  40	unsigned long magic;
  41	unsigned long size;
  42	unsigned long blocks;
  43	unsigned long files;
  44	unsigned long flags;
  45	void *linear_virt_addr;
  46	resource_size_t linear_phys_addr;
  47	size_t mtd_point_size;
  48};
  49
  50static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  51{
  52	return sb->s_fs_info;
  53}
  54
  55static const struct super_operations cramfs_ops;
  56static const struct inode_operations cramfs_dir_inode_operations;
  57static const struct file_operations cramfs_directory_operations;
  58static const struct file_operations cramfs_physmem_fops;
  59static const struct address_space_operations cramfs_aops;
  60
  61static DEFINE_MUTEX(read_mutex);
  62
  63
  64/* These macros may change in future, to provide better st_ino semantics. */
  65#define OFFSET(x)	((x)->i_ino)
  66
  67static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  68{
  69	if (!cino->offset)
  70		return offset + 1;
  71	if (!cino->size)
  72		return offset + 1;
  73
  74	/*
  75	 * The file mode test fixes buggy mkcramfs implementations where
  76	 * cramfs_inode->offset is set to a non zero value for entries
  77	 * which did not contain data, like devices node and fifos.
  78	 */
  79	switch (cino->mode & S_IFMT) {
  80	case S_IFREG:
  81	case S_IFDIR:
  82	case S_IFLNK:
  83		return cino->offset << 2;
  84	default:
  85		break;
  86	}
  87	return offset + 1;
  88}
  89
  90static struct inode *get_cramfs_inode(struct super_block *sb,
  91	const struct cramfs_inode *cramfs_inode, unsigned int offset)
  92{
  93	struct inode *inode;
  94	static struct timespec64 zerotime;
  95
  96	inode = iget_locked(sb, cramino(cramfs_inode, offset));
  97	if (!inode)
  98		return ERR_PTR(-ENOMEM);
  99	if (!(inode->i_state & I_NEW))
 100		return inode;
 101
 102	switch (cramfs_inode->mode & S_IFMT) {
 103	case S_IFREG:
 104		inode->i_fop = &generic_ro_fops;
 105		inode->i_data.a_ops = &cramfs_aops;
 106		if (IS_ENABLED(CONFIG_CRAMFS_MTD) &&
 107		    CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS &&
 108		    CRAMFS_SB(sb)->linear_phys_addr)
 109			inode->i_fop = &cramfs_physmem_fops;
 110		break;
 111	case S_IFDIR:
 112		inode->i_op = &cramfs_dir_inode_operations;
 113		inode->i_fop = &cramfs_directory_operations;
 114		break;
 115	case S_IFLNK:
 116		inode->i_op = &page_symlink_inode_operations;
 117		inode_nohighmem(inode);
 118		inode->i_data.a_ops = &cramfs_aops;
 119		break;
 120	default:
 121		init_special_inode(inode, cramfs_inode->mode,
 122				old_decode_dev(cramfs_inode->size));
 123	}
 124
 125	inode->i_mode = cramfs_inode->mode;
 126	i_uid_write(inode, cramfs_inode->uid);
 127	i_gid_write(inode, cramfs_inode->gid);
 128
 129	/* if the lower 2 bits are zero, the inode contains data */
 130	if (!(inode->i_ino & 3)) {
 131		inode->i_size = cramfs_inode->size;
 132		inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 133	}
 134
 135	/* Struct copy intentional */
 136	inode_set_mtime_to_ts(inode,
 137			      inode_set_atime_to_ts(inode, inode_set_ctime_to_ts(inode, zerotime)));
 138	/* inode->i_nlink is left 1 - arguably wrong for directories,
 139	   but it's the best we can do without reading the directory
 140	   contents.  1 yields the right result in GNU find, even
 141	   without -noleaf option. */
 142
 143	unlock_new_inode(inode);
 144
 145	return inode;
 146}
 147
 148/*
 149 * We have our own block cache: don't fill up the buffer cache
 150 * with the rom-image, because the way the filesystem is set
 151 * up the accesses should be fairly regular and cached in the
 152 * page cache and dentry tree anyway..
 153 *
 154 * This also acts as a way to guarantee contiguous areas of up to
 155 * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
 156 * worry about end-of-buffer issues even when decompressing a full
 157 * page cache.
 158 *
 159 * Note: This is all optimized away at compile time when
 160 *       CONFIG_CRAMFS_BLOCKDEV=n.
 161 */
 162#define READ_BUFFERS (2)
 163/* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 164#define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 165
 166/*
 167 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 168 * data that takes up more space than the original and with unlucky
 169 * alignment.
 170 */
 171#define BLKS_PER_BUF_SHIFT	(2)
 172#define BLKS_PER_BUF		(1 << BLKS_PER_BUF_SHIFT)
 173#define BUFFER_SIZE		(BLKS_PER_BUF*PAGE_SIZE)
 174
 175static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 176static unsigned buffer_blocknr[READ_BUFFERS];
 177static struct super_block *buffer_dev[READ_BUFFERS];
 178static int next_buffer;
 179
 180/*
 181 * Populate our block cache and return a pointer to it.
 182 */
 183static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
 184				unsigned int len)
 185{
 186	struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 187	struct file_ra_state ra = {};
 188	struct page *pages[BLKS_PER_BUF];
 189	unsigned i, blocknr, buffer;
 190	unsigned long devsize;
 191	char *data;
 192
 193	if (!len)
 194		return NULL;
 195	blocknr = offset >> PAGE_SHIFT;
 196	offset &= PAGE_SIZE - 1;
 197
 198	/* Check if an existing buffer already has the data.. */
 199	for (i = 0; i < READ_BUFFERS; i++) {
 200		unsigned int blk_offset;
 201
 202		if (buffer_dev[i] != sb)
 203			continue;
 204		if (blocknr < buffer_blocknr[i])
 205			continue;
 206		blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
 207		blk_offset += offset;
 208		if (blk_offset > BUFFER_SIZE ||
 209		    blk_offset + len > BUFFER_SIZE)
 210			continue;
 211		return read_buffers[i] + blk_offset;
 212	}
 213
 214	devsize = bdev_nr_bytes(sb->s_bdev) >> PAGE_SHIFT;
 215
 216	/* Ok, read in BLKS_PER_BUF pages completely first. */
 217	file_ra_state_init(&ra, mapping);
 218	page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
 219
 220	for (i = 0; i < BLKS_PER_BUF; i++) {
 221		struct page *page = NULL;
 222
 223		if (blocknr + i < devsize) {
 224			page = read_mapping_page(mapping, blocknr + i, NULL);
 225			/* synchronous error? */
 226			if (IS_ERR(page))
 227				page = NULL;
 228		}
 229		pages[i] = page;
 230	}
 231
 232	buffer = next_buffer;
 233	next_buffer = NEXT_BUFFER(buffer);
 234	buffer_blocknr[buffer] = blocknr;
 235	buffer_dev[buffer] = sb;
 236
 237	data = read_buffers[buffer];
 238	for (i = 0; i < BLKS_PER_BUF; i++) {
 239		struct page *page = pages[i];
 240
 241		if (page) {
 242			memcpy_from_page(data, page, 0, PAGE_SIZE);
 243			put_page(page);
 244		} else
 245			memset(data, 0, PAGE_SIZE);
 246		data += PAGE_SIZE;
 247	}
 248	return read_buffers[buffer] + offset;
 249}
 250
 251/*
 252 * Return a pointer to the linearly addressed cramfs image in memory.
 253 */
 254static void *cramfs_direct_read(struct super_block *sb, unsigned int offset,
 255				unsigned int len)
 256{
 257	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 258
 259	if (!len)
 260		return NULL;
 261	if (len > sbi->size || offset > sbi->size - len)
 262		return page_address(ZERO_PAGE(0));
 263	return sbi->linear_virt_addr + offset;
 264}
 265
 266/*
 267 * Returns a pointer to a buffer containing at least LEN bytes of
 268 * filesystem starting at byte offset OFFSET into the filesystem.
 269 */
 270static void *cramfs_read(struct super_block *sb, unsigned int offset,
 271			 unsigned int len)
 272{
 273	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 274
 275	if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sbi->linear_virt_addr)
 276		return cramfs_direct_read(sb, offset, len);
 277	else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
 278		return cramfs_blkdev_read(sb, offset, len);
 279	else
 280		return NULL;
 281}
 282
 283/*
 284 * For a mapping to be possible, we need a range of uncompressed and
 285 * contiguous blocks. Return the offset for the first block and number of
 286 * valid blocks for which that is true, or zero otherwise.
 287 */
 288static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
 289{
 290	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 291	int i;
 292	u32 *blockptrs, first_block_addr;
 293
 294	/*
 295	 * We can dereference memory directly here as this code may be
 296	 * reached only when there is a direct filesystem image mapping
 297	 * available in memory.
 298	 */
 299	blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff * 4);
 300	first_block_addr = blockptrs[0] & ~CRAMFS_BLK_FLAGS;
 301	i = 0;
 302	do {
 303		u32 block_off = i * (PAGE_SIZE >> CRAMFS_BLK_DIRECT_PTR_SHIFT);
 304		u32 expect = (first_block_addr + block_off) |
 305			     CRAMFS_BLK_FLAG_DIRECT_PTR |
 306			     CRAMFS_BLK_FLAG_UNCOMPRESSED;
 307		if (blockptrs[i] != expect) {
 308			pr_debug("range: block %d/%d got %#x expects %#x\n",
 309				 pgoff+i, pgoff + *pages - 1,
 310				 blockptrs[i], expect);
 311			if (i == 0)
 312				return 0;
 313			break;
 314		}
 315	} while (++i < *pages);
 316
 317	*pages = i;
 318	return first_block_addr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
 319}
 320
 321#ifdef CONFIG_MMU
 322
 323/*
 324 * Return true if the last page of a file in the filesystem image contains
 325 * some other data that doesn't belong to that file. It is assumed that the
 326 * last block is CRAMFS_BLK_FLAG_DIRECT_PTR | CRAMFS_BLK_FLAG_UNCOMPRESSED
 327 * (verified by cramfs_get_block_range() and directly accessible in memory.
 328 */
 329static bool cramfs_last_page_is_shared(struct inode *inode)
 330{
 331	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 332	u32 partial, last_page, blockaddr, *blockptrs;
 333	char *tail_data;
 334
 335	partial = offset_in_page(inode->i_size);
 336	if (!partial)
 337		return false;
 338	last_page = inode->i_size >> PAGE_SHIFT;
 339	blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode));
 340	blockaddr = blockptrs[last_page] & ~CRAMFS_BLK_FLAGS;
 341	blockaddr <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
 342	tail_data = sbi->linear_virt_addr + blockaddr + partial;
 343	return memchr_inv(tail_data, 0, PAGE_SIZE - partial) ? true : false;
 344}
 345
 346static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 347{
 348	struct inode *inode = file_inode(file);
 349	struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 350	unsigned int pages, max_pages, offset;
 351	unsigned long address, pgoff = vma->vm_pgoff;
 352	char *bailout_reason;
 353	int ret;
 354
 355	ret = generic_file_readonly_mmap(file, vma);
 356	if (ret)
 357		return ret;
 358
 359	/*
 360	 * Now try to pre-populate ptes for this vma with a direct
 361	 * mapping avoiding memory allocation when possible.
 362	 */
 363
 364	/* Could COW work here? */
 365	bailout_reason = "vma is writable";
 366	if (vma->vm_flags & VM_WRITE)
 367		goto bailout;
 368
 369	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 370	bailout_reason = "beyond file limit";
 371	if (pgoff >= max_pages)
 372		goto bailout;
 373	pages = min(vma_pages(vma), max_pages - pgoff);
 374
 375	offset = cramfs_get_block_range(inode, pgoff, &pages);
 376	bailout_reason = "unsuitable block layout";
 377	if (!offset)
 378		goto bailout;
 379	address = sbi->linear_phys_addr + offset;
 380	bailout_reason = "data is not page aligned";
 381	if (!PAGE_ALIGNED(address))
 382		goto bailout;
 383
 384	/* Don't map the last page if it contains some other data */
 385	if (pgoff + pages == max_pages && cramfs_last_page_is_shared(inode)) {
 386		pr_debug("mmap: %pD: last page is shared\n", file);
 387		pages--;
 388	}
 389
 390	if (!pages) {
 391		bailout_reason = "no suitable block remaining";
 392		goto bailout;
 393	}
 394
 395	if (pages == vma_pages(vma)) {
 396		/*
 397		 * The entire vma is mappable. remap_pfn_range() will
 398		 * make it distinguishable from a non-direct mapping
 399		 * in /proc/<pid>/maps by substituting the file offset
 400		 * with the actual physical address.
 401		 */
 402		ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
 403				      pages * PAGE_SIZE, vma->vm_page_prot);
 404	} else {
 405		/*
 406		 * Let's create a mixed map if we can't map it all.
 407		 * The normal paging machinery will take care of the
 408		 * unpopulated ptes via cramfs_read_folio().
 409		 */
 410		int i;
 411		vm_flags_set(vma, VM_MIXEDMAP);
 412		for (i = 0; i < pages && !ret; i++) {
 413			vm_fault_t vmf;
 414			unsigned long off = i * PAGE_SIZE;
 415			pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
 416			vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
 417			if (vmf & VM_FAULT_ERROR)
 418				ret = vm_fault_to_errno(vmf, 0);
 419		}
 420	}
 421
 422	if (!ret)
 423		pr_debug("mapped %pD[%lu] at 0x%08lx (%u/%lu pages) "
 424			 "to vma 0x%08lx, page_prot 0x%llx\n", file,
 425			 pgoff, address, pages, vma_pages(vma), vma->vm_start,
 426			 (unsigned long long)pgprot_val(vma->vm_page_prot));
 427	return ret;
 428
 429bailout:
 430	pr_debug("%pD[%lu]: direct mmap impossible: %s\n",
 431		 file, pgoff, bailout_reason);
 432	/* Didn't manage any direct map, but normal paging is still possible */
 433	return 0;
 434}
 435
 436#else /* CONFIG_MMU */
 437
 438static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 439{
 440	return is_nommu_shared_mapping(vma->vm_flags) ? 0 : -ENOSYS;
 441}
 442
 443static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
 444			unsigned long addr, unsigned long len,
 445			unsigned long pgoff, unsigned long flags)
 446{
 447	struct inode *inode = file_inode(file);
 448	struct super_block *sb = inode->i_sb;
 449	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 450	unsigned int pages, block_pages, max_pages, offset;
 451
 452	pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 453	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 454	if (pgoff >= max_pages || pages > max_pages - pgoff)
 455		return -EINVAL;
 456	block_pages = pages;
 457	offset = cramfs_get_block_range(inode, pgoff, &block_pages);
 458	if (!offset || block_pages != pages)
 459		return -ENOSYS;
 460	addr = sbi->linear_phys_addr + offset;
 461	pr_debug("get_unmapped for %pD ofs %#lx siz %lu at 0x%08lx\n",
 462		 file, pgoff*PAGE_SIZE, len, addr);
 463	return addr;
 464}
 465
 466static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
 467{
 468	return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
 469	       NOMMU_MAP_READ | NOMMU_MAP_EXEC;
 470}
 471
 472#endif /* CONFIG_MMU */
 473
 474static const struct file_operations cramfs_physmem_fops = {
 475	.llseek			= generic_file_llseek,
 476	.read_iter		= generic_file_read_iter,
 477	.splice_read		= filemap_splice_read,
 478	.mmap			= cramfs_physmem_mmap,
 479#ifndef CONFIG_MMU
 480	.get_unmapped_area	= cramfs_physmem_get_unmapped_area,
 481	.mmap_capabilities	= cramfs_physmem_mmap_capabilities,
 482#endif
 483};
 484
 485static void cramfs_kill_sb(struct super_block *sb)
 486{
 487	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 488
 489	generic_shutdown_super(sb);
 490
 491	if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sb->s_mtd) {
 492		if (sbi && sbi->mtd_point_size)
 493			mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
 494		put_mtd_device(sb->s_mtd);
 495		sb->s_mtd = NULL;
 496	} else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
 497		sync_blockdev(sb->s_bdev);
 498		bdev_release(sb->s_bdev_handle);
 499	}
 500	kfree(sbi);
 501}
 502
 503static int cramfs_reconfigure(struct fs_context *fc)
 504{
 505	sync_filesystem(fc->root->d_sb);
 506	fc->sb_flags |= SB_RDONLY;
 507	return 0;
 508}
 509
 510static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
 511			     struct cramfs_super *super)
 512{
 513	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 514	unsigned long root_offset;
 515	bool silent = fc->sb_flags & SB_SILENT;
 516
 517	/* We don't know the real size yet */
 518	sbi->size = PAGE_SIZE;
 519
 520	/* Read the first block and get the superblock from it */
 521	mutex_lock(&read_mutex);
 522	memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super));
 523	mutex_unlock(&read_mutex);
 524
 525	/* Do sanity checks on the superblock */
 526	if (super->magic != CRAMFS_MAGIC) {
 527		/* check for wrong endianness */
 528		if (super->magic == CRAMFS_MAGIC_WEND) {
 529			if (!silent)
 530				errorfc(fc, "wrong endianness");
 531			return -EINVAL;
 532		}
 533
 534		/* check at 512 byte offset */
 535		mutex_lock(&read_mutex);
 536		memcpy(super,
 537		       cramfs_read(sb, 512, sizeof(*super)),
 538		       sizeof(*super));
 539		mutex_unlock(&read_mutex);
 540		if (super->magic != CRAMFS_MAGIC) {
 541			if (super->magic == CRAMFS_MAGIC_WEND && !silent)
 542				errorfc(fc, "wrong endianness");
 543			else if (!silent)
 544				errorfc(fc, "wrong magic");
 545			return -EINVAL;
 546		}
 547	}
 548
 549	/* get feature flags first */
 550	if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
 551		errorfc(fc, "unsupported filesystem features");
 552		return -EINVAL;
 553	}
 554
 555	/* Check that the root inode is in a sane state */
 556	if (!S_ISDIR(super->root.mode)) {
 557		errorfc(fc, "root is not a directory");
 558		return -EINVAL;
 559	}
 560	/* correct strange, hard-coded permissions of mkcramfs */
 561	super->root.mode |= 0555;
 562
 563	root_offset = super->root.offset << 2;
 564	if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) {
 565		sbi->size = super->size;
 566		sbi->blocks = super->fsid.blocks;
 567		sbi->files = super->fsid.files;
 568	} else {
 569		sbi->size = 1<<28;
 570		sbi->blocks = 0;
 571		sbi->files = 0;
 572	}
 573	sbi->magic = super->magic;
 574	sbi->flags = super->flags;
 575	if (root_offset == 0)
 576		infofc(fc, "empty filesystem");
 577	else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 578		 ((root_offset != sizeof(struct cramfs_super)) &&
 579		  (root_offset != 512 + sizeof(struct cramfs_super))))
 580	{
 581		errorfc(fc, "bad root offset %lu", root_offset);
 582		return -EINVAL;
 583	}
 584
 585	return 0;
 586}
 587
 588static int cramfs_finalize_super(struct super_block *sb,
 589				 struct cramfs_inode *cramfs_root)
 590{
 591	struct inode *root;
 592
 593	/* Set it all up.. */
 594	sb->s_flags |= SB_RDONLY;
 595	sb->s_time_min = 0;
 596	sb->s_time_max = 0;
 597	sb->s_op = &cramfs_ops;
 598	root = get_cramfs_inode(sb, cramfs_root, 0);
 599	if (IS_ERR(root))
 600		return PTR_ERR(root);
 601	sb->s_root = d_make_root(root);
 602	if (!sb->s_root)
 603		return -ENOMEM;
 604	return 0;
 605}
 606
 607static int cramfs_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
 608{
 609	struct cramfs_sb_info *sbi;
 610	struct cramfs_super super;
 611	int i, err;
 612
 613	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 614	if (!sbi)
 615		return -ENOMEM;
 616	sb->s_fs_info = sbi;
 617
 618	/* Invalidate the read buffers on mount: think disk change.. */
 619	for (i = 0; i < READ_BUFFERS; i++)
 620		buffer_blocknr[i] = -1;
 621
 622	err = cramfs_read_super(sb, fc, &super);
 623	if (err)
 624		return err;
 625	return cramfs_finalize_super(sb, &super.root);
 626}
 627
 628static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
 629{
 630	struct cramfs_sb_info *sbi;
 631	struct cramfs_super super;
 632	int err;
 633
 634	sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 635	if (!sbi)
 636		return -ENOMEM;
 637	sb->s_fs_info = sbi;
 638
 639	/* Map only one page for now.  Will remap it when fs size is known. */
 640	err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
 641			&sbi->linear_virt_addr, &sbi->linear_phys_addr);
 642	if (err || sbi->mtd_point_size != PAGE_SIZE) {
 643		pr_err("unable to get direct memory access to mtd:%s\n",
 644		       sb->s_mtd->name);
 645		return err ? : -ENODATA;
 646	}
 647
 648	pr_info("checking physical address %pap for linear cramfs image\n",
 649		&sbi->linear_phys_addr);
 650	err = cramfs_read_super(sb, fc, &super);
 651	if (err)
 652		return err;
 653
 654	/* Remap the whole filesystem now */
 655	pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
 656		sb->s_mtd->name, sbi->size/1024);
 657	mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
 658	err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
 659			&sbi->linear_virt_addr, &sbi->linear_phys_addr);
 660	if (err || sbi->mtd_point_size != sbi->size) {
 661		pr_err("unable to get direct memory access to mtd:%s\n",
 662		       sb->s_mtd->name);
 663		return err ? : -ENODATA;
 664	}
 665
 666	return cramfs_finalize_super(sb, &super.root);
 667}
 668
 669static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 670{
 671	struct super_block *sb = dentry->d_sb;
 672	u64 id = 0;
 673
 674	if (sb->s_bdev)
 675		id = huge_encode_dev(sb->s_bdev->bd_dev);
 676	else if (sb->s_dev)
 677		id = huge_encode_dev(sb->s_dev);
 678
 679	buf->f_type = CRAMFS_MAGIC;
 680	buf->f_bsize = PAGE_SIZE;
 681	buf->f_blocks = CRAMFS_SB(sb)->blocks;
 682	buf->f_bfree = 0;
 683	buf->f_bavail = 0;
 684	buf->f_files = CRAMFS_SB(sb)->files;
 685	buf->f_ffree = 0;
 686	buf->f_fsid = u64_to_fsid(id);
 687	buf->f_namelen = CRAMFS_MAXPATHLEN;
 688	return 0;
 689}
 690
 691/*
 692 * Read a cramfs directory entry.
 693 */
 694static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 695{
 696	struct inode *inode = file_inode(file);
 697	struct super_block *sb = inode->i_sb;
 698	char *buf;
 699	unsigned int offset;
 700
 701	/* Offset within the thing. */
 702	if (ctx->pos >= inode->i_size)
 703		return 0;
 704	offset = ctx->pos;
 705	/* Directory entries are always 4-byte aligned */
 706	if (offset & 3)
 707		return -EINVAL;
 708
 709	buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 710	if (!buf)
 711		return -ENOMEM;
 712
 713	while (offset < inode->i_size) {
 714		struct cramfs_inode *de;
 715		unsigned long nextoffset;
 716		char *name;
 717		ino_t ino;
 718		umode_t mode;
 719		int namelen;
 720
 721		mutex_lock(&read_mutex);
 722		de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 723		name = (char *)(de+1);
 724
 725		/*
 726		 * Namelengths on disk are shifted by two
 727		 * and the name padded out to 4-byte boundaries
 728		 * with zeroes.
 729		 */
 730		namelen = de->namelen << 2;
 731		memcpy(buf, name, namelen);
 732		ino = cramino(de, OFFSET(inode) + offset);
 733		mode = de->mode;
 734		mutex_unlock(&read_mutex);
 735		nextoffset = offset + sizeof(*de) + namelen;
 736		for (;;) {
 737			if (!namelen) {
 738				kfree(buf);
 739				return -EIO;
 740			}
 741			if (buf[namelen-1])
 742				break;
 743			namelen--;
 744		}
 745		if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 746			break;
 747
 748		ctx->pos = offset = nextoffset;
 749	}
 750	kfree(buf);
 751	return 0;
 752}
 753
 754/*
 755 * Lookup and fill in the inode data..
 756 */
 757static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 758{
 759	unsigned int offset = 0;
 760	struct inode *inode = NULL;
 761	int sorted;
 762
 763	mutex_lock(&read_mutex);
 764	sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 765	while (offset < dir->i_size) {
 766		struct cramfs_inode *de;
 767		char *name;
 768		int namelen, retval;
 769		int dir_off = OFFSET(dir) + offset;
 770
 771		de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 772		name = (char *)(de+1);
 773
 774		/* Try to take advantage of sorted directories */
 775		if (sorted && (dentry->d_name.name[0] < name[0]))
 776			break;
 777
 778		namelen = de->namelen << 2;
 779		offset += sizeof(*de) + namelen;
 780
 781		/* Quick check that the name is roughly the right length */
 782		if (((dentry->d_name.len + 3) & ~3) != namelen)
 783			continue;
 784
 785		for (;;) {
 786			if (!namelen) {
 787				inode = ERR_PTR(-EIO);
 788				goto out;
 789			}
 790			if (name[namelen-1])
 791				break;
 792			namelen--;
 793		}
 794		if (namelen != dentry->d_name.len)
 795			continue;
 796		retval = memcmp(dentry->d_name.name, name, namelen);
 797		if (retval > 0)
 798			continue;
 799		if (!retval) {
 800			inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 801			break;
 802		}
 803		/* else (retval < 0) */
 804		if (sorted)
 805			break;
 806	}
 807out:
 808	mutex_unlock(&read_mutex);
 809	return d_splice_alias(inode, dentry);
 810}
 811
 812static int cramfs_read_folio(struct file *file, struct folio *folio)
 813{
 814	struct page *page = &folio->page;
 815	struct inode *inode = page->mapping->host;
 816	u32 maxblock;
 817	int bytes_filled;
 818	void *pgdata;
 
 819
 820	maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 821	bytes_filled = 0;
 822	pgdata = kmap_local_page(page);
 823
 824	if (page->index < maxblock) {
 825		struct super_block *sb = inode->i_sb;
 826		u32 blkptr_offset = OFFSET(inode) + page->index * 4;
 827		u32 block_ptr, block_start, block_len;
 828		bool uncompressed, direct;
 829
 830		mutex_lock(&read_mutex);
 831		block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
 832		uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
 833		direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
 834		block_ptr &= ~CRAMFS_BLK_FLAGS;
 835
 836		if (direct) {
 837			/*
 838			 * The block pointer is an absolute start pointer,
 839			 * shifted by 2 bits. The size is included in the
 840			 * first 2 bytes of the data block when compressed,
 841			 * or PAGE_SIZE otherwise.
 842			 */
 843			block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
 844			if (uncompressed) {
 845				block_len = PAGE_SIZE;
 846				/* if last block: cap to file length */
 847				if (page->index == maxblock - 1)
 848					block_len =
 849						offset_in_page(inode->i_size);
 850			} else {
 851				block_len = *(u16 *)
 852					cramfs_read(sb, block_start, 2);
 853				block_start += 2;
 854			}
 855		} else {
 856			/*
 857			 * The block pointer indicates one past the end of
 858			 * the current block (start of next block). If this
 859			 * is the first block then it starts where the block
 860			 * pointer table ends, otherwise its start comes
 861			 * from the previous block's pointer.
 862			 */
 863			block_start = OFFSET(inode) + maxblock * 4;
 864			if (page->index)
 865				block_start = *(u32 *)
 866					cramfs_read(sb, blkptr_offset - 4, 4);
 867			/* Beware... previous ptr might be a direct ptr */
 868			if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
 869				/* See comments on earlier code. */
 870				u32 prev_start = block_start;
 871				block_start = prev_start & ~CRAMFS_BLK_FLAGS;
 872				block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
 873				if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
 874					block_start += PAGE_SIZE;
 875				} else {
 876					block_len = *(u16 *)
 877						cramfs_read(sb, block_start, 2);
 878					block_start += 2 + block_len;
 879				}
 880			}
 881			block_start &= ~CRAMFS_BLK_FLAGS;
 882			block_len = block_ptr - block_start;
 883		}
 884
 885		if (block_len == 0)
 886			; /* hole */
 887		else if (unlikely(block_len > 2*PAGE_SIZE ||
 888				  (uncompressed && block_len > PAGE_SIZE))) {
 889			mutex_unlock(&read_mutex);
 890			pr_err("bad data blocksize %u\n", block_len);
 891			goto err;
 892		} else if (uncompressed) {
 893			memcpy(pgdata,
 894			       cramfs_read(sb, block_start, block_len),
 895			       block_len);
 896			bytes_filled = block_len;
 897		} else {
 898			bytes_filled = cramfs_uncompress_block(pgdata,
 899				 PAGE_SIZE,
 900				 cramfs_read(sb, block_start, block_len),
 901				 block_len);
 902		}
 903		mutex_unlock(&read_mutex);
 904		if (unlikely(bytes_filled < 0))
 905			goto err;
 906	}
 907
 908	memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
 909	flush_dcache_page(page);
 910	kunmap_local(pgdata);
 911	SetPageUptodate(page);
 912	unlock_page(page);
 913	return 0;
 914
 
 915err:
 916	kunmap_local(pgdata);
 917	ClearPageUptodate(page);
 918	SetPageError(page);
 919	unlock_page(page);
 920	return 0;
 921}
 922
 923static const struct address_space_operations cramfs_aops = {
 924	.read_folio = cramfs_read_folio
 925};
 926
 927/*
 928 * Our operations:
 929 */
 930
 931/*
 932 * A directory can only readdir
 933 */
 934static const struct file_operations cramfs_directory_operations = {
 935	.llseek		= generic_file_llseek,
 936	.read		= generic_read_dir,
 937	.iterate_shared	= cramfs_readdir,
 938};
 939
 940static const struct inode_operations cramfs_dir_inode_operations = {
 941	.lookup		= cramfs_lookup,
 942};
 943
 944static const struct super_operations cramfs_ops = {
 945	.statfs		= cramfs_statfs,
 946};
 947
 948static int cramfs_get_tree(struct fs_context *fc)
 949{
 950	int ret = -ENOPROTOOPT;
 951
 952	if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
 953		ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
 954		if (!ret)
 955			return 0;
 956	}
 957	if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
 958		ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
 959	return ret;
 960}
 961
 962static const struct fs_context_operations cramfs_context_ops = {
 963	.get_tree	= cramfs_get_tree,
 964	.reconfigure	= cramfs_reconfigure,
 965};
 966
 967/*
 968 * Set up the filesystem mount context.
 969 */
 970static int cramfs_init_fs_context(struct fs_context *fc)
 971{
 972	fc->ops = &cramfs_context_ops;
 973	return 0;
 974}
 975
 976static struct file_system_type cramfs_fs_type = {
 977	.owner		= THIS_MODULE,
 978	.name		= "cramfs",
 979	.init_fs_context = cramfs_init_fs_context,
 980	.kill_sb	= cramfs_kill_sb,
 981	.fs_flags	= FS_REQUIRES_DEV,
 982};
 983MODULE_ALIAS_FS("cramfs");
 984
 985static int __init init_cramfs_fs(void)
 986{
 987	int rv;
 988
 989	rv = cramfs_uncompress_init();
 990	if (rv < 0)
 991		return rv;
 992	rv = register_filesystem(&cramfs_fs_type);
 993	if (rv < 0)
 994		cramfs_uncompress_exit();
 995	return rv;
 996}
 997
 998static void __exit exit_cramfs_fs(void)
 999{
1000	cramfs_uncompress_exit();
1001	unregister_filesystem(&cramfs_fs_type);
1002}
1003
1004module_init(init_cramfs_fs)
1005module_exit(exit_cramfs_fs)
 
1006MODULE_LICENSE("GPL");