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_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
175 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
176 static unsigned buffer_blocknr[READ_BUFFERS];
177 static struct super_block *buffer_dev[READ_BUFFERS];
178 static int next_buffer;
179
180 /*
181 * Populate our block cache and return a pointer to it.
182 */
183 static 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_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 */
254 static 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 */
270 static 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 */
288 static 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 */
329 static 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
346 static 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
429 bailout:
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
438 static 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
443 static 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
466 static 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
474 static 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
485 static 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_fput(sb->s_bdev_file);
499 }
500 kfree(sbi);
501 }
502
503 static 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
510 static 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
588 static 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
607 static 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
628 static 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
669 static 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 */
694 static 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 */
757 static 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 }
807 out:
808 mutex_unlock(&read_mutex);
809 return d_splice_alias(inode, dentry);
810 }
811
812 static int cramfs_read_folio(struct file *file, struct folio *folio)
813 {
814 struct inode *inode = folio->mapping->host;
815 u32 maxblock;
816 int bytes_filled;
817 void *pgdata;
818 bool success = false;
819
820 maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
821 bytes_filled = 0;
822 pgdata = kmap_local_folio(folio, 0);
823
824 if (folio->index < maxblock) {
825 struct super_block *sb = inode->i_sb;
826 u32 blkptr_offset = OFFSET(inode) + folio->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 (folio->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 (folio->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_folio(folio);
910
911 success = true;
912 err:
913 kunmap_local(pgdata);
914 folio_end_read(folio, success);
915 return 0;
916 }
917
918 static const struct address_space_operations cramfs_aops = {
919 .read_folio = cramfs_read_folio
920 };
921
922 /*
923 * Our operations:
924 */
925
926 /*
927 * A directory can only readdir
928 */
929 static const struct file_operations cramfs_directory_operations = {
930 .llseek = generic_file_llseek,
931 .read = generic_read_dir,
932 .iterate_shared = cramfs_readdir,
933 };
934
935 static const struct inode_operations cramfs_dir_inode_operations = {
936 .lookup = cramfs_lookup,
937 };
938
939 static const struct super_operations cramfs_ops = {
940 .statfs = cramfs_statfs,
941 };
942
943 static int cramfs_get_tree(struct fs_context *fc)
944 {
945 int ret = -ENOPROTOOPT;
946
947 if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
948 ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
949 if (!ret)
950 return 0;
951 }
952 if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
953 ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
954 return ret;
955 }
956
957 static const struct fs_context_operations cramfs_context_ops = {
958 .get_tree = cramfs_get_tree,
959 .reconfigure = cramfs_reconfigure,
960 };
961
962 /*
963 * Set up the filesystem mount context.
964 */
965 static int cramfs_init_fs_context(struct fs_context *fc)
966 {
967 fc->ops = &cramfs_context_ops;
968 return 0;
969 }
970
971 static struct file_system_type cramfs_fs_type = {
972 .owner = THIS_MODULE,
973 .name = "cramfs",
974 .init_fs_context = cramfs_init_fs_context,
975 .kill_sb = cramfs_kill_sb,
976 .fs_flags = FS_REQUIRES_DEV,
977 };
978 MODULE_ALIAS_FS("cramfs");
979
980 static int __init init_cramfs_fs(void)
981 {
982 int rv;
983
984 rv = cramfs_uncompress_init();
985 if (rv < 0)
986 return rv;
987 rv = register_filesystem(&cramfs_fs_type);
988 if (rv < 0)
989 cramfs_uncompress_exit();
990 return rv;
991 }
992
993 static void __exit exit_cramfs_fs(void)
994 {
995 cramfs_uncompress_exit();
996 unregister_filesystem(&cramfs_fs_type);
997 }
998
999 module_init(init_cramfs_fs)
1000 module_exit(exit_cramfs_fs)
1001 MODULE_DESCRIPTION("Compressed ROM file system support");
1002 MODULE_LICENSE("GPL");
1003
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