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/ramfs.h>
21 #include <linux/init.h>
22 #include <linux/string.h>
23 #include <linux/blkdev.h>
24 #include <linux/mtd/mtd.h>
25 #include <linux/mtd/super.h>
26 #include <linux/fs_context.h>
27 #include <linux/slab.h>
28 #include <linux/vfs.h>
29 #include <linux/mutex.h>
30 #include <uapi/linux/cramfs_fs.h>
31 #include <linux/uaccess.h>
32
33 #include "internal.h"
34
35 /*
36 * cramfs super-block data in memory
37 */
38 struct cramfs_sb_info {
39 unsigned long magic;
40 unsigned long size;
41 unsigned long blocks;
42 unsigned long files;
43 unsigned long flags;
44 void *linear_virt_addr;
45 resource_size_t linear_phys_addr;
46 size_t mtd_point_size;
47 };
48
CRAMFS_SB(struct super_block * sb)49 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
50 {
51 return sb->s_fs_info;
52 }
53
54 static const struct super_operations cramfs_ops;
55 static const struct inode_operations cramfs_dir_inode_operations;
56 static const struct file_operations cramfs_directory_operations;
57 static const struct file_operations cramfs_physmem_fops;
58 static const struct address_space_operations cramfs_aops;
59
60 static DEFINE_MUTEX(read_mutex);
61
62
63 /* These macros may change in future, to provide better st_ino semantics. */
64 #define OFFSET(x) ((x)->i_ino)
65
cramino(const struct cramfs_inode * cino,unsigned int offset)66 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
67 {
68 if (!cino->offset)
69 return offset + 1;
70 if (!cino->size)
71 return offset + 1;
72
73 /*
74 * The file mode test fixes buggy mkcramfs implementations where
75 * cramfs_inode->offset is set to a non zero value for entries
76 * which did not contain data, like devices node and fifos.
77 */
78 switch (cino->mode & S_IFMT) {
79 case S_IFREG:
80 case S_IFDIR:
81 case S_IFLNK:
82 return cino->offset << 2;
83 default:
84 break;
85 }
86 return offset + 1;
87 }
88
get_cramfs_inode(struct super_block * sb,const struct cramfs_inode * cramfs_inode,unsigned int offset)89 static struct inode *get_cramfs_inode(struct super_block *sb,
90 const struct cramfs_inode *cramfs_inode, unsigned int offset)
91 {
92 struct inode *inode;
93 static struct timespec64 zerotime;
94
95 inode = iget_locked(sb, cramino(cramfs_inode, offset));
96 if (!inode)
97 return ERR_PTR(-ENOMEM);
98 if (!(inode->i_state & I_NEW))
99 return inode;
100
101 switch (cramfs_inode->mode & S_IFMT) {
102 case S_IFREG:
103 inode->i_fop = &generic_ro_fops;
104 inode->i_data.a_ops = &cramfs_aops;
105 if (IS_ENABLED(CONFIG_CRAMFS_MTD) &&
106 CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS &&
107 CRAMFS_SB(sb)->linear_phys_addr)
108 inode->i_fop = &cramfs_physmem_fops;
109 break;
110 case S_IFDIR:
111 inode->i_op = &cramfs_dir_inode_operations;
112 inode->i_fop = &cramfs_directory_operations;
113 break;
114 case S_IFLNK:
115 inode->i_op = &page_symlink_inode_operations;
116 inode_nohighmem(inode);
117 inode->i_data.a_ops = &cramfs_aops;
118 break;
119 case S_IFCHR:
120 case S_IFBLK:
121 case S_IFIFO:
122 case S_IFSOCK:
123 init_special_inode(inode, cramfs_inode->mode,
124 old_decode_dev(cramfs_inode->size));
125 break;
126 default:
127 printk(KERN_DEBUG "CRAMFS: Invalid file type 0%04o for inode %lu.\n",
128 inode->i_mode, inode->i_ino);
129 iget_failed(inode);
130 return ERR_PTR(-EIO);
131 }
132
133 inode->i_mode = cramfs_inode->mode;
134 i_uid_write(inode, cramfs_inode->uid);
135 i_gid_write(inode, cramfs_inode->gid);
136
137 /* if the lower 2 bits are zero, the inode contains data */
138 if (!(inode->i_ino & 3)) {
139 inode->i_size = cramfs_inode->size;
140 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
141 }
142
143 /* Struct copy intentional */
144 inode_set_mtime_to_ts(inode,
145 inode_set_atime_to_ts(inode, inode_set_ctime_to_ts(inode, zerotime)));
146 /* inode->i_nlink is left 1 - arguably wrong for directories,
147 but it's the best we can do without reading the directory
148 contents. 1 yields the right result in GNU find, even
149 without -noleaf option. */
150
151 unlock_new_inode(inode);
152
153 return inode;
154 }
155
156 /*
157 * We have our own block cache: don't fill up the buffer cache
158 * with the rom-image, because the way the filesystem is set
159 * up the accesses should be fairly regular and cached in the
160 * page cache and dentry tree anyway..
161 *
162 * This also acts as a way to guarantee contiguous areas of up to
163 * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
164 * worry about end-of-buffer issues even when decompressing a full
165 * page cache.
166 *
167 * Note: This is all optimized away at compile time when
168 * CONFIG_CRAMFS_BLOCKDEV=n.
169 */
170 #define READ_BUFFERS (2)
171 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
172 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
173
174 /*
175 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
176 * data that takes up more space than the original and with unlucky
177 * alignment.
178 */
179 #define BLKS_PER_BUF_SHIFT (2)
180 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
181 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_SIZE)
182
183 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
184 static unsigned buffer_blocknr[READ_BUFFERS];
185 static struct super_block *buffer_dev[READ_BUFFERS];
186 static int next_buffer;
187
188 /*
189 * Populate our block cache and return a pointer to it.
190 */
cramfs_blkdev_read(struct super_block * sb,unsigned int offset,unsigned int len)191 static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
192 unsigned int len)
193 {
194 struct address_space *mapping = sb->s_bdev->bd_mapping;
195 struct file_ra_state ra = {};
196 struct page *pages[BLKS_PER_BUF];
197 unsigned i, blocknr, buffer;
198 unsigned long devsize;
199 char *data;
200
201 if (!len)
202 return NULL;
203 blocknr = offset >> PAGE_SHIFT;
204 offset &= PAGE_SIZE - 1;
205
206 /* Check if an existing buffer already has the data.. */
207 for (i = 0; i < READ_BUFFERS; i++) {
208 unsigned int blk_offset;
209
210 if (buffer_dev[i] != sb)
211 continue;
212 if (blocknr < buffer_blocknr[i])
213 continue;
214 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
215 blk_offset += offset;
216 if (blk_offset > BUFFER_SIZE ||
217 blk_offset + len > BUFFER_SIZE)
218 continue;
219 return read_buffers[i] + blk_offset;
220 }
221
222 devsize = bdev_nr_bytes(sb->s_bdev) >> PAGE_SHIFT;
223
224 /* Ok, read in BLKS_PER_BUF pages completely first. */
225 file_ra_state_init(&ra, mapping);
226 page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
227
228 for (i = 0; i < BLKS_PER_BUF; i++) {
229 struct page *page = NULL;
230
231 if (blocknr + i < devsize) {
232 page = read_mapping_page(mapping, blocknr + i, NULL);
233 /* synchronous error? */
234 if (IS_ERR(page))
235 page = NULL;
236 }
237 pages[i] = page;
238 }
239
240 buffer = next_buffer;
241 next_buffer = NEXT_BUFFER(buffer);
242 buffer_blocknr[buffer] = blocknr;
243 buffer_dev[buffer] = sb;
244
245 data = read_buffers[buffer];
246 for (i = 0; i < BLKS_PER_BUF; i++) {
247 struct page *page = pages[i];
248
249 if (page) {
250 memcpy_from_page(data, page, 0, PAGE_SIZE);
251 put_page(page);
252 } else
253 memset(data, 0, PAGE_SIZE);
254 data += PAGE_SIZE;
255 }
256 return read_buffers[buffer] + offset;
257 }
258
259 /*
260 * Return a pointer to the linearly addressed cramfs image in memory.
261 */
cramfs_direct_read(struct super_block * sb,unsigned int offset,unsigned int len)262 static void *cramfs_direct_read(struct super_block *sb, unsigned int offset,
263 unsigned int len)
264 {
265 struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
266
267 if (!len)
268 return NULL;
269 if (len > sbi->size || offset > sbi->size - len)
270 return page_address(ZERO_PAGE(0));
271 return sbi->linear_virt_addr + offset;
272 }
273
274 /*
275 * Returns a pointer to a buffer containing at least LEN bytes of
276 * filesystem starting at byte offset OFFSET into the filesystem.
277 */
cramfs_read(struct super_block * sb,unsigned int offset,unsigned int len)278 static void *cramfs_read(struct super_block *sb, unsigned int offset,
279 unsigned int len)
280 {
281 struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
282
283 if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sbi->linear_virt_addr)
284 return cramfs_direct_read(sb, offset, len);
285 else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
286 return cramfs_blkdev_read(sb, offset, len);
287 else
288 return NULL;
289 }
290
291 /*
292 * For a mapping to be possible, we need a range of uncompressed and
293 * contiguous blocks. Return the offset for the first block and number of
294 * valid blocks for which that is true, or zero otherwise.
295 */
cramfs_get_block_range(struct inode * inode,u32 pgoff,u32 * pages)296 static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
297 {
298 struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
299 int i;
300 u32 *blockptrs, first_block_addr;
301
302 /*
303 * We can dereference memory directly here as this code may be
304 * reached only when there is a direct filesystem image mapping
305 * available in memory.
306 */
307 blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff * 4);
308 first_block_addr = blockptrs[0] & ~CRAMFS_BLK_FLAGS;
309 i = 0;
310 do {
311 u32 block_off = i * (PAGE_SIZE >> CRAMFS_BLK_DIRECT_PTR_SHIFT);
312 u32 expect = (first_block_addr + block_off) |
313 CRAMFS_BLK_FLAG_DIRECT_PTR |
314 CRAMFS_BLK_FLAG_UNCOMPRESSED;
315 if (blockptrs[i] != expect) {
316 pr_debug("range: block %d/%d got %#x expects %#x\n",
317 pgoff+i, pgoff + *pages - 1,
318 blockptrs[i], expect);
319 if (i == 0)
320 return 0;
321 break;
322 }
323 } while (++i < *pages);
324
325 *pages = i;
326 return first_block_addr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
327 }
328
329 #ifdef CONFIG_MMU
330
331 /*
332 * Return true if the last page of a file in the filesystem image contains
333 * some other data that doesn't belong to that file. It is assumed that the
334 * last block is CRAMFS_BLK_FLAG_DIRECT_PTR | CRAMFS_BLK_FLAG_UNCOMPRESSED
335 * (verified by cramfs_get_block_range() and directly accessible in memory.
336 */
cramfs_last_page_is_shared(struct inode * inode)337 static bool cramfs_last_page_is_shared(struct inode *inode)
338 {
339 struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
340 u32 partial, last_page, blockaddr, *blockptrs;
341 char *tail_data;
342
343 partial = offset_in_page(inode->i_size);
344 if (!partial)
345 return false;
346 last_page = inode->i_size >> PAGE_SHIFT;
347 blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode));
348 blockaddr = blockptrs[last_page] & ~CRAMFS_BLK_FLAGS;
349 blockaddr <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
350 tail_data = sbi->linear_virt_addr + blockaddr + partial;
351 return memchr_inv(tail_data, 0, PAGE_SIZE - partial) ? true : false;
352 }
353
cramfs_physmem_mmap(struct file * file,struct vm_area_struct * vma)354 static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
355 {
356 struct inode *inode = file_inode(file);
357 struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
358 unsigned int pages, max_pages, offset;
359 unsigned long address, pgoff = vma->vm_pgoff;
360 char *bailout_reason;
361 int ret;
362
363 ret = generic_file_readonly_mmap(file, vma);
364 if (ret)
365 return ret;
366
367 /*
368 * Now try to pre-populate ptes for this vma with a direct
369 * mapping avoiding memory allocation when possible.
370 */
371
372 /* Could COW work here? */
373 bailout_reason = "vma is writable";
374 if (vma->vm_flags & VM_WRITE)
375 goto bailout;
376
377 max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
378 bailout_reason = "beyond file limit";
379 if (pgoff >= max_pages)
380 goto bailout;
381 pages = min(vma_pages(vma), max_pages - pgoff);
382
383 offset = cramfs_get_block_range(inode, pgoff, &pages);
384 bailout_reason = "unsuitable block layout";
385 if (!offset)
386 goto bailout;
387 address = sbi->linear_phys_addr + offset;
388 bailout_reason = "data is not page aligned";
389 if (!PAGE_ALIGNED(address))
390 goto bailout;
391
392 /* Don't map the last page if it contains some other data */
393 if (pgoff + pages == max_pages && cramfs_last_page_is_shared(inode)) {
394 pr_debug("mmap: %pD: last page is shared\n", file);
395 pages--;
396 }
397
398 if (!pages) {
399 bailout_reason = "no suitable block remaining";
400 goto bailout;
401 }
402
403 if (pages == vma_pages(vma)) {
404 /*
405 * The entire vma is mappable. remap_pfn_range() will
406 * make it distinguishable from a non-direct mapping
407 * in /proc/<pid>/maps by substituting the file offset
408 * with the actual physical address.
409 */
410 ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
411 pages * PAGE_SIZE, vma->vm_page_prot);
412 } else {
413 /*
414 * Let's create a mixed map if we can't map it all.
415 * The normal paging machinery will take care of the
416 * unpopulated ptes via cramfs_read_folio().
417 */
418 int i;
419 vm_flags_set(vma, VM_MIXEDMAP);
420 for (i = 0; i < pages && !ret; i++) {
421 vm_fault_t vmf;
422 unsigned long off = i * PAGE_SIZE;
423 vmf = vmf_insert_mixed(vma, vma->vm_start + off,
424 PHYS_PFN(address + off));
425 if (vmf & VM_FAULT_ERROR)
426 ret = vm_fault_to_errno(vmf, 0);
427 }
428 }
429
430 if (!ret)
431 pr_debug("mapped %pD[%lu] at 0x%08lx (%u/%lu pages) "
432 "to vma 0x%08lx, page_prot 0x%llx\n", file,
433 pgoff, address, pages, vma_pages(vma), vma->vm_start,
434 (unsigned long long)pgprot_val(vma->vm_page_prot));
435 return ret;
436
437 bailout:
438 pr_debug("%pD[%lu]: direct mmap impossible: %s\n",
439 file, pgoff, bailout_reason);
440 /* Didn't manage any direct map, but normal paging is still possible */
441 return 0;
442 }
443
444 #else /* CONFIG_MMU */
445
cramfs_physmem_mmap(struct file * file,struct vm_area_struct * vma)446 static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
447 {
448 return is_nommu_shared_mapping(vma->vm_flags) ? 0 : -ENOSYS;
449 }
450
cramfs_physmem_get_unmapped_area(struct file * file,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)451 static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
452 unsigned long addr, unsigned long len,
453 unsigned long pgoff, unsigned long flags)
454 {
455 struct inode *inode = file_inode(file);
456 struct super_block *sb = inode->i_sb;
457 struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
458 unsigned int pages, block_pages, max_pages, offset;
459
460 pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
461 max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
462 if (pgoff >= max_pages || pages > max_pages - pgoff)
463 return -EINVAL;
464 block_pages = pages;
465 offset = cramfs_get_block_range(inode, pgoff, &block_pages);
466 if (!offset || block_pages != pages)
467 return -ENOSYS;
468 addr = sbi->linear_phys_addr + offset;
469 pr_debug("get_unmapped for %pD ofs %#lx siz %lu at 0x%08lx\n",
470 file, pgoff*PAGE_SIZE, len, addr);
471 return addr;
472 }
473
cramfs_physmem_mmap_capabilities(struct file * file)474 static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
475 {
476 return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
477 NOMMU_MAP_READ | NOMMU_MAP_EXEC;
478 }
479
480 #endif /* CONFIG_MMU */
481
482 static const struct file_operations cramfs_physmem_fops = {
483 .llseek = generic_file_llseek,
484 .read_iter = generic_file_read_iter,
485 .splice_read = filemap_splice_read,
486 .mmap = cramfs_physmem_mmap,
487 #ifndef CONFIG_MMU
488 .get_unmapped_area = cramfs_physmem_get_unmapped_area,
489 .mmap_capabilities = cramfs_physmem_mmap_capabilities,
490 #endif
491 };
492
cramfs_kill_sb(struct super_block * sb)493 static void cramfs_kill_sb(struct super_block *sb)
494 {
495 struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
496
497 generic_shutdown_super(sb);
498
499 if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sb->s_mtd) {
500 if (sbi && sbi->mtd_point_size)
501 mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
502 put_mtd_device(sb->s_mtd);
503 sb->s_mtd = NULL;
504 } else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
505 sync_blockdev(sb->s_bdev);
506 bdev_fput(sb->s_bdev_file);
507 }
508 kfree(sbi);
509 }
510
cramfs_reconfigure(struct fs_context * fc)511 static int cramfs_reconfigure(struct fs_context *fc)
512 {
513 sync_filesystem(fc->root->d_sb);
514 fc->sb_flags |= SB_RDONLY;
515 return 0;
516 }
517
cramfs_read_super(struct super_block * sb,struct fs_context * fc,struct cramfs_super * super)518 static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
519 struct cramfs_super *super)
520 {
521 struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
522 unsigned long root_offset;
523 bool silent = fc->sb_flags & SB_SILENT;
524
525 /* We don't know the real size yet */
526 sbi->size = PAGE_SIZE;
527
528 /* Read the first block and get the superblock from it */
529 mutex_lock(&read_mutex);
530 memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super));
531 mutex_unlock(&read_mutex);
532
533 /* Do sanity checks on the superblock */
534 if (super->magic != CRAMFS_MAGIC) {
535 /* check for wrong endianness */
536 if (super->magic == CRAMFS_MAGIC_WEND) {
537 if (!silent)
538 errorfc(fc, "wrong endianness");
539 return -EINVAL;
540 }
541
542 /* check at 512 byte offset */
543 mutex_lock(&read_mutex);
544 memcpy(super,
545 cramfs_read(sb, 512, sizeof(*super)),
546 sizeof(*super));
547 mutex_unlock(&read_mutex);
548 if (super->magic != CRAMFS_MAGIC) {
549 if (super->magic == CRAMFS_MAGIC_WEND && !silent)
550 errorfc(fc, "wrong endianness");
551 else if (!silent)
552 errorfc(fc, "wrong magic");
553 return -EINVAL;
554 }
555 }
556
557 /* get feature flags first */
558 if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
559 errorfc(fc, "unsupported filesystem features");
560 return -EINVAL;
561 }
562
563 /* Check that the root inode is in a sane state */
564 if (!S_ISDIR(super->root.mode)) {
565 errorfc(fc, "root is not a directory");
566 return -EINVAL;
567 }
568 /* correct strange, hard-coded permissions of mkcramfs */
569 super->root.mode |= 0555;
570
571 root_offset = super->root.offset << 2;
572 if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) {
573 sbi->size = super->size;
574 sbi->blocks = super->fsid.blocks;
575 sbi->files = super->fsid.files;
576 } else {
577 sbi->size = 1<<28;
578 sbi->blocks = 0;
579 sbi->files = 0;
580 }
581 sbi->magic = super->magic;
582 sbi->flags = super->flags;
583 if (root_offset == 0)
584 infofc(fc, "empty filesystem");
585 else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
586 ((root_offset != sizeof(struct cramfs_super)) &&
587 (root_offset != 512 + sizeof(struct cramfs_super))))
588 {
589 errorfc(fc, "bad root offset %lu", root_offset);
590 return -EINVAL;
591 }
592
593 return 0;
594 }
595
cramfs_finalize_super(struct super_block * sb,struct cramfs_inode * cramfs_root)596 static int cramfs_finalize_super(struct super_block *sb,
597 struct cramfs_inode *cramfs_root)
598 {
599 struct inode *root;
600
601 /* Set it all up.. */
602 sb->s_flags |= SB_RDONLY;
603 sb->s_time_min = 0;
604 sb->s_time_max = 0;
605 sb->s_op = &cramfs_ops;
606 root = get_cramfs_inode(sb, cramfs_root, 0);
607 if (IS_ERR(root))
608 return PTR_ERR(root);
609 sb->s_root = d_make_root(root);
610 if (!sb->s_root)
611 return -ENOMEM;
612 return 0;
613 }
614
cramfs_blkdev_fill_super(struct super_block * sb,struct fs_context * fc)615 static int cramfs_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
616 {
617 struct cramfs_sb_info *sbi;
618 struct cramfs_super super;
619 int i, err;
620
621 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
622 if (!sbi)
623 return -ENOMEM;
624 sb->s_fs_info = sbi;
625
626 /* Invalidate the read buffers on mount: think disk change.. */
627 for (i = 0; i < READ_BUFFERS; i++)
628 buffer_blocknr[i] = -1;
629
630 err = cramfs_read_super(sb, fc, &super);
631 if (err)
632 return err;
633 return cramfs_finalize_super(sb, &super.root);
634 }
635
cramfs_mtd_fill_super(struct super_block * sb,struct fs_context * fc)636 static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
637 {
638 struct cramfs_sb_info *sbi;
639 struct cramfs_super super;
640 int err;
641
642 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
643 if (!sbi)
644 return -ENOMEM;
645 sb->s_fs_info = sbi;
646
647 /* Map only one page for now. Will remap it when fs size is known. */
648 err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
649 &sbi->linear_virt_addr, &sbi->linear_phys_addr);
650 if (err || sbi->mtd_point_size != PAGE_SIZE) {
651 pr_err("unable to get direct memory access to mtd:%s\n",
652 sb->s_mtd->name);
653 return err ? : -ENODATA;
654 }
655
656 pr_info("checking physical address %pap for linear cramfs image\n",
657 &sbi->linear_phys_addr);
658 err = cramfs_read_super(sb, fc, &super);
659 if (err)
660 return err;
661
662 /* Remap the whole filesystem now */
663 pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
664 sb->s_mtd->name, sbi->size/1024);
665 mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
666 err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
667 &sbi->linear_virt_addr, &sbi->linear_phys_addr);
668 if (err || sbi->mtd_point_size != sbi->size) {
669 pr_err("unable to get direct memory access to mtd:%s\n",
670 sb->s_mtd->name);
671 return err ? : -ENODATA;
672 }
673
674 return cramfs_finalize_super(sb, &super.root);
675 }
676
cramfs_statfs(struct dentry * dentry,struct kstatfs * buf)677 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
678 {
679 struct super_block *sb = dentry->d_sb;
680 u64 id = 0;
681
682 if (sb->s_bdev)
683 id = huge_encode_dev(sb->s_bdev->bd_dev);
684 else if (sb->s_dev)
685 id = huge_encode_dev(sb->s_dev);
686
687 buf->f_type = CRAMFS_MAGIC;
688 buf->f_bsize = PAGE_SIZE;
689 buf->f_blocks = CRAMFS_SB(sb)->blocks;
690 buf->f_bfree = 0;
691 buf->f_bavail = 0;
692 buf->f_files = CRAMFS_SB(sb)->files;
693 buf->f_ffree = 0;
694 buf->f_fsid = u64_to_fsid(id);
695 buf->f_namelen = CRAMFS_MAXPATHLEN;
696 return 0;
697 }
698
699 /*
700 * Read a cramfs directory entry.
701 */
cramfs_readdir(struct file * file,struct dir_context * ctx)702 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
703 {
704 struct inode *inode = file_inode(file);
705 struct super_block *sb = inode->i_sb;
706 char *buf;
707 unsigned int offset;
708
709 /* Offset within the thing. */
710 if (ctx->pos >= inode->i_size)
711 return 0;
712 offset = ctx->pos;
713 /* Directory entries are always 4-byte aligned */
714 if (offset & 3)
715 return -EINVAL;
716
717 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
718 if (!buf)
719 return -ENOMEM;
720
721 while (offset < inode->i_size) {
722 struct cramfs_inode *de;
723 unsigned long nextoffset;
724 char *name;
725 ino_t ino;
726 umode_t mode;
727 int namelen;
728
729 mutex_lock(&read_mutex);
730 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
731 name = (char *)(de+1);
732
733 /*
734 * Namelengths on disk are shifted by two
735 * and the name padded out to 4-byte boundaries
736 * with zeroes.
737 */
738 namelen = de->namelen << 2;
739 memcpy(buf, name, namelen);
740 ino = cramino(de, OFFSET(inode) + offset);
741 mode = de->mode;
742 mutex_unlock(&read_mutex);
743 nextoffset = offset + sizeof(*de) + namelen;
744 for (;;) {
745 if (!namelen) {
746 kfree(buf);
747 return -EIO;
748 }
749 if (buf[namelen-1])
750 break;
751 namelen--;
752 }
753 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
754 break;
755
756 ctx->pos = offset = nextoffset;
757 }
758 kfree(buf);
759 return 0;
760 }
761
762 /*
763 * Lookup and fill in the inode data..
764 */
cramfs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)765 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
766 {
767 unsigned int offset = 0;
768 struct inode *inode = NULL;
769 int sorted;
770
771 mutex_lock(&read_mutex);
772 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
773 while (offset < dir->i_size) {
774 struct cramfs_inode *de;
775 char *name;
776 int namelen, retval;
777 int dir_off = OFFSET(dir) + offset;
778
779 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
780 name = (char *)(de+1);
781
782 /* Try to take advantage of sorted directories */
783 if (sorted && (dentry->d_name.name[0] < name[0]))
784 break;
785
786 namelen = de->namelen << 2;
787 offset += sizeof(*de) + namelen;
788
789 /* Quick check that the name is roughly the right length */
790 if (((dentry->d_name.len + 3) & ~3) != namelen)
791 continue;
792
793 for (;;) {
794 if (!namelen) {
795 inode = ERR_PTR(-EIO);
796 goto out;
797 }
798 if (name[namelen-1])
799 break;
800 namelen--;
801 }
802 if (namelen != dentry->d_name.len)
803 continue;
804 retval = memcmp(dentry->d_name.name, name, namelen);
805 if (retval > 0)
806 continue;
807 if (!retval) {
808 inode = get_cramfs_inode(dir->i_sb, de, dir_off);
809 break;
810 }
811 /* else (retval < 0) */
812 if (sorted)
813 break;
814 }
815 out:
816 mutex_unlock(&read_mutex);
817 return d_splice_alias(inode, dentry);
818 }
819
cramfs_read_folio(struct file * file,struct folio * folio)820 static int cramfs_read_folio(struct file *file, struct folio *folio)
821 {
822 struct inode *inode = folio->mapping->host;
823 u32 maxblock;
824 int bytes_filled;
825 void *pgdata;
826 bool success = false;
827
828 maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
829 bytes_filled = 0;
830 pgdata = kmap_local_folio(folio, 0);
831
832 if (folio->index < maxblock) {
833 struct super_block *sb = inode->i_sb;
834 u32 blkptr_offset = OFFSET(inode) + folio->index * 4;
835 u32 block_ptr, block_start, block_len;
836 bool uncompressed, direct;
837
838 mutex_lock(&read_mutex);
839 block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
840 uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
841 direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
842 block_ptr &= ~CRAMFS_BLK_FLAGS;
843
844 if (direct) {
845 /*
846 * The block pointer is an absolute start pointer,
847 * shifted by 2 bits. The size is included in the
848 * first 2 bytes of the data block when compressed,
849 * or PAGE_SIZE otherwise.
850 */
851 block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
852 if (uncompressed) {
853 block_len = PAGE_SIZE;
854 /* if last block: cap to file length */
855 if (folio->index == maxblock - 1)
856 block_len =
857 offset_in_page(inode->i_size);
858 } else {
859 block_len = *(u16 *)
860 cramfs_read(sb, block_start, 2);
861 block_start += 2;
862 }
863 } else {
864 /*
865 * The block pointer indicates one past the end of
866 * the current block (start of next block). If this
867 * is the first block then it starts where the block
868 * pointer table ends, otherwise its start comes
869 * from the previous block's pointer.
870 */
871 block_start = OFFSET(inode) + maxblock * 4;
872 if (folio->index)
873 block_start = *(u32 *)
874 cramfs_read(sb, blkptr_offset - 4, 4);
875 /* Beware... previous ptr might be a direct ptr */
876 if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
877 /* See comments on earlier code. */
878 u32 prev_start = block_start;
879 block_start = prev_start & ~CRAMFS_BLK_FLAGS;
880 block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
881 if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
882 block_start += PAGE_SIZE;
883 } else {
884 block_len = *(u16 *)
885 cramfs_read(sb, block_start, 2);
886 block_start += 2 + block_len;
887 }
888 }
889 block_start &= ~CRAMFS_BLK_FLAGS;
890 block_len = block_ptr - block_start;
891 }
892
893 if (block_len == 0)
894 ; /* hole */
895 else if (unlikely(block_len > 2*PAGE_SIZE ||
896 (uncompressed && block_len > PAGE_SIZE))) {
897 mutex_unlock(&read_mutex);
898 pr_err("bad data blocksize %u\n", block_len);
899 goto err;
900 } else if (uncompressed) {
901 memcpy(pgdata,
902 cramfs_read(sb, block_start, block_len),
903 block_len);
904 bytes_filled = block_len;
905 } else {
906 bytes_filled = cramfs_uncompress_block(pgdata,
907 PAGE_SIZE,
908 cramfs_read(sb, block_start, block_len),
909 block_len);
910 }
911 mutex_unlock(&read_mutex);
912 if (unlikely(bytes_filled < 0))
913 goto err;
914 }
915
916 memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
917 flush_dcache_folio(folio);
918
919 success = true;
920 err:
921 kunmap_local(pgdata);
922 folio_end_read(folio, success);
923 return 0;
924 }
925
926 static const struct address_space_operations cramfs_aops = {
927 .read_folio = cramfs_read_folio
928 };
929
930 /*
931 * Our operations:
932 */
933
934 /*
935 * A directory can only readdir
936 */
937 static const struct file_operations cramfs_directory_operations = {
938 .llseek = generic_file_llseek,
939 .read = generic_read_dir,
940 .iterate_shared = cramfs_readdir,
941 };
942
943 static const struct inode_operations cramfs_dir_inode_operations = {
944 .lookup = cramfs_lookup,
945 };
946
947 static const struct super_operations cramfs_ops = {
948 .statfs = cramfs_statfs,
949 };
950
cramfs_get_tree(struct fs_context * fc)951 static int cramfs_get_tree(struct fs_context *fc)
952 {
953 int ret = -ENOPROTOOPT;
954
955 if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
956 ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
957 if (!ret)
958 return 0;
959 }
960 if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
961 ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
962 return ret;
963 }
964
965 static const struct fs_context_operations cramfs_context_ops = {
966 .get_tree = cramfs_get_tree,
967 .reconfigure = cramfs_reconfigure,
968 };
969
970 /*
971 * Set up the filesystem mount context.
972 */
cramfs_init_fs_context(struct fs_context * fc)973 static int cramfs_init_fs_context(struct fs_context *fc)
974 {
975 fc->ops = &cramfs_context_ops;
976 return 0;
977 }
978
979 static struct file_system_type cramfs_fs_type = {
980 .owner = THIS_MODULE,
981 .name = "cramfs",
982 .init_fs_context = cramfs_init_fs_context,
983 .kill_sb = cramfs_kill_sb,
984 .fs_flags = FS_REQUIRES_DEV,
985 };
986 MODULE_ALIAS_FS("cramfs");
987
init_cramfs_fs(void)988 static int __init init_cramfs_fs(void)
989 {
990 int rv;
991
992 rv = cramfs_uncompress_init();
993 if (rv < 0)
994 return rv;
995 rv = register_filesystem(&cramfs_fs_type);
996 if (rv < 0)
997 cramfs_uncompress_exit();
998 return rv;
999 }
1000
exit_cramfs_fs(void)1001 static void __exit exit_cramfs_fs(void)
1002 {
1003 cramfs_uncompress_exit();
1004 unregister_filesystem(&cramfs_fs_type);
1005 }
1006
1007 module_init(init_cramfs_fs)
1008 module_exit(exit_cramfs_fs)
1009 MODULE_DESCRIPTION("Compressed ROM file system support");
1010 MODULE_LICENSE("GPL");
1011