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