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TOMOYO Linux Cross Reference
Linux/fs/cramfs/inode.c

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  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/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 
 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 
 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 
 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         default:
120                 init_special_inode(inode, cramfs_inode->mode,
121                                 old_decode_dev(cramfs_inode->size));
122         }
123 
124         inode->i_mode = cramfs_inode->mode;
125         i_uid_write(inode, cramfs_inode->uid);
126         i_gid_write(inode, cramfs_inode->gid);
127 
128         /* if the lower 2 bits are zero, the inode contains data */
129         if (!(inode->i_ino & 3)) {
130                 inode->i_size = cramfs_inode->size;
131                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
132         }
133 
134         /* Struct copy intentional */
135         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
136         /* inode->i_nlink is left 1 - arguably wrong for directories,
137            but it's the best we can do without reading the directory
138            contents.  1 yields the right result in GNU find, even
139            without -noleaf option. */
140 
141         unlock_new_inode(inode);
142 
143         return inode;
144 }
145 
146 /*
147  * We have our own block cache: don't fill up the buffer cache
148  * with the rom-image, because the way the filesystem is set
149  * up the accesses should be fairly regular and cached in the
150  * page cache and dentry tree anyway..
151  *
152  * This also acts as a way to guarantee contiguous areas of up to
153  * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
154  * worry about end-of-buffer issues even when decompressing a full
155  * page cache.
156  *
157  * Note: This is all optimized away at compile time when
158  *       CONFIG_CRAMFS_BLOCKDEV=n.
159  */
160 #define READ_BUFFERS (2)
161 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
162 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
163 
164 /*
165  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
166  * data that takes up more space than the original and with unlucky
167  * alignment.
168  */
169 #define BLKS_PER_BUF_SHIFT      (2)
170 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
171 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_SIZE)
172 
173 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
174 static unsigned buffer_blocknr[READ_BUFFERS];
175 static struct super_block *buffer_dev[READ_BUFFERS];
176 static int next_buffer;
177 
178 /*
179  * Populate our block cache and return a pointer to it.
180  */
181 static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
182                                 unsigned int len)
183 {
184         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
185         struct page *pages[BLKS_PER_BUF];
186         unsigned i, blocknr, buffer;
187         unsigned long devsize;
188         char *data;
189 
190         if (!len)
191                 return NULL;
192         blocknr = offset >> PAGE_SHIFT;
193         offset &= PAGE_SIZE - 1;
194 
195         /* Check if an existing buffer already has the data.. */
196         for (i = 0; i < READ_BUFFERS; i++) {
197                 unsigned int blk_offset;
198 
199                 if (buffer_dev[i] != sb)
200                         continue;
201                 if (blocknr < buffer_blocknr[i])
202                         continue;
203                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
204                 blk_offset += offset;
205                 if (blk_offset > BUFFER_SIZE ||
206                     blk_offset + len > BUFFER_SIZE)
207                         continue;
208                 return read_buffers[i] + blk_offset;
209         }
210 
211         devsize = mapping->host->i_size >> PAGE_SHIFT;
212 
213         /* Ok, read in BLKS_PER_BUF pages completely first. */
214         for (i = 0; i < BLKS_PER_BUF; i++) {
215                 struct page *page = NULL;
216 
217                 if (blocknr + i < devsize) {
218                         page = read_mapping_page(mapping, blocknr + i, NULL);
219                         /* synchronous error? */
220                         if (IS_ERR(page))
221                                 page = NULL;
222                 }
223                 pages[i] = page;
224         }
225 
226         for (i = 0; i < BLKS_PER_BUF; i++) {
227                 struct page *page = pages[i];
228 
229                 if (page) {
230                         wait_on_page_locked(page);
231                         if (!PageUptodate(page)) {
232                                 /* asynchronous error */
233                                 put_page(page);
234                                 pages[i] = NULL;
235                         }
236                 }
237         }
238 
239         buffer = next_buffer;
240         next_buffer = NEXT_BUFFER(buffer);
241         buffer_blocknr[buffer] = blocknr;
242         buffer_dev[buffer] = sb;
243 
244         data = read_buffers[buffer];
245         for (i = 0; i < BLKS_PER_BUF; i++) {
246                 struct page *page = pages[i];
247 
248                 if (page) {
249                         memcpy(data, kmap(page), PAGE_SIZE);
250                         kunmap(page);
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  */
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  */
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  */
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  */
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 
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: %s: last page is shared\n",
395                          file_dentry(file)->d_name.name);
396                 pages--;
397         }
398 
399         if (!pages) {
400                 bailout_reason = "no suitable block remaining";
401                 goto bailout;
402         }
403 
404         if (pages == vma_pages(vma)) {
405                 /*
406                  * The entire vma is mappable. remap_pfn_range() will
407                  * make it distinguishable from a non-direct mapping
408                  * in /proc/<pid>/maps by substituting the file offset
409                  * with the actual physical address.
410                  */
411                 ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
412                                       pages * PAGE_SIZE, vma->vm_page_prot);
413         } else {
414                 /*
415                  * Let's create a mixed map if we can't map it all.
416                  * The normal paging machinery will take care of the
417                  * unpopulated ptes via cramfs_readpage().
418                  */
419                 int i;
420                 vma->vm_flags |= VM_MIXEDMAP;
421                 for (i = 0; i < pages && !ret; i++) {
422                         vm_fault_t vmf;
423                         unsigned long off = i * PAGE_SIZE;
424                         pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
425                         vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
426                         if (vmf & VM_FAULT_ERROR)
427                                 ret = vm_fault_to_errno(vmf, 0);
428                 }
429         }
430 
431         if (!ret)
432                 pr_debug("mapped %s[%lu] at 0x%08lx (%u/%lu pages) "
433                          "to vma 0x%08lx, page_prot 0x%llx\n",
434                          file_dentry(file)->d_name.name, pgoff,
435                          address, pages, vma_pages(vma), vma->vm_start,
436                          (unsigned long long)pgprot_val(vma->vm_page_prot));
437         return ret;
438 
439 bailout:
440         pr_debug("%s[%lu]: direct mmap impossible: %s\n",
441                  file_dentry(file)->d_name.name, pgoff, bailout_reason);
442         /* Didn't manage any direct map, but normal paging is still possible */
443         return 0;
444 }
445 
446 #else /* CONFIG_MMU */
447 
448 static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
449 {
450         return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
451 }
452 
453 static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
454                         unsigned long addr, unsigned long len,
455                         unsigned long pgoff, unsigned long flags)
456 {
457         struct inode *inode = file_inode(file);
458         struct super_block *sb = inode->i_sb;
459         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
460         unsigned int pages, block_pages, max_pages, offset;
461 
462         pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
463         max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
464         if (pgoff >= max_pages || pages > max_pages - pgoff)
465                 return -EINVAL;
466         block_pages = pages;
467         offset = cramfs_get_block_range(inode, pgoff, &block_pages);
468         if (!offset || block_pages != pages)
469                 return -ENOSYS;
470         addr = sbi->linear_phys_addr + offset;
471         pr_debug("get_unmapped for %s ofs %#lx siz %lu at 0x%08lx\n",
472                  file_dentry(file)->d_name.name, pgoff*PAGE_SIZE, len, addr);
473         return addr;
474 }
475 
476 static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
477 {
478         return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
479                NOMMU_MAP_READ | NOMMU_MAP_EXEC;
480 }
481 
482 #endif /* CONFIG_MMU */
483 
484 static const struct file_operations cramfs_physmem_fops = {
485         .llseek                 = generic_file_llseek,
486         .read_iter              = generic_file_read_iter,
487         .splice_read            = generic_file_splice_read,
488         .mmap                   = cramfs_physmem_mmap,
489 #ifndef CONFIG_MMU
490         .get_unmapped_area      = cramfs_physmem_get_unmapped_area,
491         .mmap_capabilities      = cramfs_physmem_mmap_capabilities,
492 #endif
493 };
494 
495 static void cramfs_kill_sb(struct super_block *sb)
496 {
497         struct cramfs_sb_info *sbi = CRAMFS_SB(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                 kill_mtd_super(sb);
503         } else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
504                 kill_block_super(sb);
505         }
506         kfree(sbi);
507 }
508 
509 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
510 {
511         sync_filesystem(sb);
512         *flags |= SB_RDONLY;
513         return 0;
514 }
515 
516 static int cramfs_read_super(struct super_block *sb,
517                              struct cramfs_super *super, int silent)
518 {
519         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
520         unsigned long root_offset;
521 
522         /* We don't know the real size yet */
523         sbi->size = PAGE_SIZE;
524 
525         /* Read the first block and get the superblock from it */
526         mutex_lock(&read_mutex);
527         memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super));
528         mutex_unlock(&read_mutex);
529 
530         /* Do sanity checks on the superblock */
531         if (super->magic != CRAMFS_MAGIC) {
532                 /* check for wrong endianness */
533                 if (super->magic == CRAMFS_MAGIC_WEND) {
534                         if (!silent)
535                                 pr_err("wrong endianness\n");
536                         return -EINVAL;
537                 }
538 
539                 /* check at 512 byte offset */
540                 mutex_lock(&read_mutex);
541                 memcpy(super,
542                        cramfs_read(sb, 512, sizeof(*super)),
543                        sizeof(*super));
544                 mutex_unlock(&read_mutex);
545                 if (super->magic != CRAMFS_MAGIC) {
546                         if (super->magic == CRAMFS_MAGIC_WEND && !silent)
547                                 pr_err("wrong endianness\n");
548                         else if (!silent)
549                                 pr_err("wrong magic\n");
550                         return -EINVAL;
551                 }
552         }
553 
554         /* get feature flags first */
555         if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
556                 pr_err("unsupported filesystem features\n");
557                 return -EINVAL;
558         }
559 
560         /* Check that the root inode is in a sane state */
561         if (!S_ISDIR(super->root.mode)) {
562                 pr_err("root is not a directory\n");
563                 return -EINVAL;
564         }
565         /* correct strange, hard-coded permissions of mkcramfs */
566         super->root.mode |= 0555;
567 
568         root_offset = super->root.offset << 2;
569         if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) {
570                 sbi->size = super->size;
571                 sbi->blocks = super->fsid.blocks;
572                 sbi->files = super->fsid.files;
573         } else {
574                 sbi->size = 1<<28;
575                 sbi->blocks = 0;
576                 sbi->files = 0;
577         }
578         sbi->magic = super->magic;
579         sbi->flags = super->flags;
580         if (root_offset == 0)
581                 pr_info("empty filesystem");
582         else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
583                  ((root_offset != sizeof(struct cramfs_super)) &&
584                   (root_offset != 512 + sizeof(struct cramfs_super))))
585         {
586                 pr_err("bad root offset %lu\n", root_offset);
587                 return -EINVAL;
588         }
589 
590         return 0;
591 }
592 
593 static int cramfs_finalize_super(struct super_block *sb,
594                                  struct cramfs_inode *cramfs_root)
595 {
596         struct inode *root;
597 
598         /* Set it all up.. */
599         sb->s_flags |= SB_RDONLY;
600         sb->s_op = &cramfs_ops;
601         root = get_cramfs_inode(sb, cramfs_root, 0);
602         if (IS_ERR(root))
603                 return PTR_ERR(root);
604         sb->s_root = d_make_root(root);
605         if (!sb->s_root)
606                 return -ENOMEM;
607         return 0;
608 }
609 
610 static int cramfs_blkdev_fill_super(struct super_block *sb, void *data,
611                                     int silent)
612 {
613         struct cramfs_sb_info *sbi;
614         struct cramfs_super super;
615         int i, err;
616 
617         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
618         if (!sbi)
619                 return -ENOMEM;
620         sb->s_fs_info = sbi;
621 
622         /* Invalidate the read buffers on mount: think disk change.. */
623         for (i = 0; i < READ_BUFFERS; i++)
624                 buffer_blocknr[i] = -1;
625 
626         err = cramfs_read_super(sb, &super, silent);
627         if (err)
628                 return err;
629         return cramfs_finalize_super(sb, &super.root);
630 }
631 
632 static int cramfs_mtd_fill_super(struct super_block *sb, void *data,
633                                  int silent)
634 {
635         struct cramfs_sb_info *sbi;
636         struct cramfs_super super;
637         int err;
638 
639         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
640         if (!sbi)
641                 return -ENOMEM;
642         sb->s_fs_info = sbi;
643 
644         /* Map only one page for now.  Will remap it when fs size is known. */
645         err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
646                         &sbi->linear_virt_addr, &sbi->linear_phys_addr);
647         if (err || sbi->mtd_point_size != PAGE_SIZE) {
648                 pr_err("unable to get direct memory access to mtd:%s\n",
649                        sb->s_mtd->name);
650                 return err ? : -ENODATA;
651         }
652 
653         pr_info("checking physical address %pap for linear cramfs image\n",
654                 &sbi->linear_phys_addr);
655         err = cramfs_read_super(sb, &super, silent);
656         if (err)
657                 return err;
658 
659         /* Remap the whole filesystem now */
660         pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
661                 sb->s_mtd->name, sbi->size/1024);
662         mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
663         err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
664                         &sbi->linear_virt_addr, &sbi->linear_phys_addr);
665         if (err || sbi->mtd_point_size != sbi->size) {
666                 pr_err("unable to get direct memory access to mtd:%s\n",
667                        sb->s_mtd->name);
668                 return err ? : -ENODATA;
669         }
670 
671         return cramfs_finalize_super(sb, &super.root);
672 }
673 
674 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
675 {
676         struct super_block *sb = dentry->d_sb;
677         u64 id = 0;
678 
679         if (sb->s_bdev)
680                 id = huge_encode_dev(sb->s_bdev->bd_dev);
681         else if (sb->s_dev)
682                 id = huge_encode_dev(sb->s_dev);
683 
684         buf->f_type = CRAMFS_MAGIC;
685         buf->f_bsize = PAGE_SIZE;
686         buf->f_blocks = CRAMFS_SB(sb)->blocks;
687         buf->f_bfree = 0;
688         buf->f_bavail = 0;
689         buf->f_files = CRAMFS_SB(sb)->files;
690         buf->f_ffree = 0;
691         buf->f_fsid.val[0] = (u32)id;
692         buf->f_fsid.val[1] = (u32)(id >> 32);
693         buf->f_namelen = CRAMFS_MAXPATHLEN;
694         return 0;
695 }
696 
697 /*
698  * Read a cramfs directory entry.
699  */
700 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
701 {
702         struct inode *inode = file_inode(file);
703         struct super_block *sb = inode->i_sb;
704         char *buf;
705         unsigned int offset;
706 
707         /* Offset within the thing. */
708         if (ctx->pos >= inode->i_size)
709                 return 0;
710         offset = ctx->pos;
711         /* Directory entries are always 4-byte aligned */
712         if (offset & 3)
713                 return -EINVAL;
714 
715         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
716         if (!buf)
717                 return -ENOMEM;
718 
719         while (offset < inode->i_size) {
720                 struct cramfs_inode *de;
721                 unsigned long nextoffset;
722                 char *name;
723                 ino_t ino;
724                 umode_t mode;
725                 int namelen;
726 
727                 mutex_lock(&read_mutex);
728                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
729                 name = (char *)(de+1);
730 
731                 /*
732                  * Namelengths on disk are shifted by two
733                  * and the name padded out to 4-byte boundaries
734                  * with zeroes.
735                  */
736                 namelen = de->namelen << 2;
737                 memcpy(buf, name, namelen);
738                 ino = cramino(de, OFFSET(inode) + offset);
739                 mode = de->mode;
740                 mutex_unlock(&read_mutex);
741                 nextoffset = offset + sizeof(*de) + namelen;
742                 for (;;) {
743                         if (!namelen) {
744                                 kfree(buf);
745                                 return -EIO;
746                         }
747                         if (buf[namelen-1])
748                                 break;
749                         namelen--;
750                 }
751                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
752                         break;
753 
754                 ctx->pos = offset = nextoffset;
755         }
756         kfree(buf);
757         return 0;
758 }
759 
760 /*
761  * Lookup and fill in the inode data..
762  */
763 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
764 {
765         unsigned int offset = 0;
766         struct inode *inode = NULL;
767         int sorted;
768 
769         mutex_lock(&read_mutex);
770         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
771         while (offset < dir->i_size) {
772                 struct cramfs_inode *de;
773                 char *name;
774                 int namelen, retval;
775                 int dir_off = OFFSET(dir) + offset;
776 
777                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
778                 name = (char *)(de+1);
779 
780                 /* Try to take advantage of sorted directories */
781                 if (sorted && (dentry->d_name.name[0] < name[0]))
782                         break;
783 
784                 namelen = de->namelen << 2;
785                 offset += sizeof(*de) + namelen;
786 
787                 /* Quick check that the name is roughly the right length */
788                 if (((dentry->d_name.len + 3) & ~3) != namelen)
789                         continue;
790 
791                 for (;;) {
792                         if (!namelen) {
793                                 inode = ERR_PTR(-EIO);
794                                 goto out;
795                         }
796                         if (name[namelen-1])
797                                 break;
798                         namelen--;
799                 }
800                 if (namelen != dentry->d_name.len)
801                         continue;
802                 retval = memcmp(dentry->d_name.name, name, namelen);
803                 if (retval > 0)
804                         continue;
805                 if (!retval) {
806                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
807                         break;
808                 }
809                 /* else (retval < 0) */
810                 if (sorted)
811                         break;
812         }
813 out:
814         mutex_unlock(&read_mutex);
815         return d_splice_alias(inode, dentry);
816 }
817 
818 static int cramfs_readpage(struct file *file, struct page *page)
819 {
820         struct inode *inode = page->mapping->host;
821         u32 maxblock;
822         int bytes_filled;
823         void *pgdata;
824 
825         maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
826         bytes_filled = 0;
827         pgdata = kmap(page);
828 
829         if (page->index < maxblock) {
830                 struct super_block *sb = inode->i_sb;
831                 u32 blkptr_offset = OFFSET(inode) + page->index * 4;
832                 u32 block_ptr, block_start, block_len;
833                 bool uncompressed, direct;
834 
835                 mutex_lock(&read_mutex);
836                 block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
837                 uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
838                 direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
839                 block_ptr &= ~CRAMFS_BLK_FLAGS;
840 
841                 if (direct) {
842                         /*
843                          * The block pointer is an absolute start pointer,
844                          * shifted by 2 bits. The size is included in the
845                          * first 2 bytes of the data block when compressed,
846                          * or PAGE_SIZE otherwise.
847                          */
848                         block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
849                         if (uncompressed) {
850                                 block_len = PAGE_SIZE;
851                                 /* if last block: cap to file length */
852                                 if (page->index == maxblock - 1)
853                                         block_len =
854                                                 offset_in_page(inode->i_size);
855                         } else {
856                                 block_len = *(u16 *)
857                                         cramfs_read(sb, block_start, 2);
858                                 block_start += 2;
859                         }
860                 } else {
861                         /*
862                          * The block pointer indicates one past the end of
863                          * the current block (start of next block). If this
864                          * is the first block then it starts where the block
865                          * pointer table ends, otherwise its start comes
866                          * from the previous block's pointer.
867                          */
868                         block_start = OFFSET(inode) + maxblock * 4;
869                         if (page->index)
870                                 block_start = *(u32 *)
871                                         cramfs_read(sb, blkptr_offset - 4, 4);
872                         /* Beware... previous ptr might be a direct ptr */
873                         if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
874                                 /* See comments on earlier code. */
875                                 u32 prev_start = block_start;
876                                 block_start = prev_start & ~CRAMFS_BLK_FLAGS;
877                                 block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
878                                 if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
879                                         block_start += PAGE_SIZE;
880                                 } else {
881                                         block_len = *(u16 *)
882                                                 cramfs_read(sb, block_start, 2);
883                                         block_start += 2 + block_len;
884                                 }
885                         }
886                         block_start &= ~CRAMFS_BLK_FLAGS;
887                         block_len = block_ptr - block_start;
888                 }
889 
890                 if (block_len == 0)
891                         ; /* hole */
892                 else if (unlikely(block_len > 2*PAGE_SIZE ||
893                                   (uncompressed && block_len > PAGE_SIZE))) {
894                         mutex_unlock(&read_mutex);
895                         pr_err("bad data blocksize %u\n", block_len);
896                         goto err;
897                 } else if (uncompressed) {
898                         memcpy(pgdata,
899                                cramfs_read(sb, block_start, block_len),
900                                block_len);
901                         bytes_filled = block_len;
902                 } else {
903                         bytes_filled = cramfs_uncompress_block(pgdata,
904                                  PAGE_SIZE,
905                                  cramfs_read(sb, block_start, block_len),
906                                  block_len);
907                 }
908                 mutex_unlock(&read_mutex);
909                 if (unlikely(bytes_filled < 0))
910                         goto err;
911         }
912 
913         memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
914         flush_dcache_page(page);
915         kunmap(page);
916         SetPageUptodate(page);
917         unlock_page(page);
918         return 0;
919 
920 err:
921         kunmap(page);
922         ClearPageUptodate(page);
923         SetPageError(page);
924         unlock_page(page);
925         return 0;
926 }
927 
928 static const struct address_space_operations cramfs_aops = {
929         .readpage = cramfs_readpage
930 };
931 
932 /*
933  * Our operations:
934  */
935 
936 /*
937  * A directory can only readdir
938  */
939 static const struct file_operations cramfs_directory_operations = {
940         .llseek         = generic_file_llseek,
941         .read           = generic_read_dir,
942         .iterate_shared = cramfs_readdir,
943 };
944 
945 static const struct inode_operations cramfs_dir_inode_operations = {
946         .lookup         = cramfs_lookup,
947 };
948 
949 static const struct super_operations cramfs_ops = {
950         .remount_fs     = cramfs_remount,
951         .statfs         = cramfs_statfs,
952 };
953 
954 static struct dentry *cramfs_mount(struct file_system_type *fs_type, int flags,
955                                    const char *dev_name, void *data)
956 {
957         struct dentry *ret = ERR_PTR(-ENOPROTOOPT);
958 
959         if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
960                 ret = mount_mtd(fs_type, flags, dev_name, data,
961                                 cramfs_mtd_fill_super);
962                 if (!IS_ERR(ret))
963                         return ret;
964         }
965         if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV)) {
966                 ret = mount_bdev(fs_type, flags, dev_name, data,
967                                  cramfs_blkdev_fill_super);
968         }
969         return ret;
970 }
971 
972 static struct file_system_type cramfs_fs_type = {
973         .owner          = THIS_MODULE,
974         .name           = "cramfs",
975         .mount          = cramfs_mount,
976         .kill_sb        = cramfs_kill_sb,
977         .fs_flags       = FS_REQUIRES_DEV,
978 };
979 MODULE_ALIAS_FS("cramfs");
980 
981 static int __init init_cramfs_fs(void)
982 {
983         int rv;
984 
985         rv = cramfs_uncompress_init();
986         if (rv < 0)
987                 return rv;
988         rv = register_filesystem(&cramfs_fs_type);
989         if (rv < 0)
990                 cramfs_uncompress_exit();
991         return rv;
992 }
993 
994 static void __exit exit_cramfs_fs(void)
995 {
996         cramfs_uncompress_exit();
997         unregister_filesystem(&cramfs_fs_type);
998 }
999 
1000 module_init(init_cramfs_fs)
1001 module_exit(exit_cramfs_fs)
1002 MODULE_LICENSE("GPL");
1003 

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