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Linux/fs/sysv/super.c

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  1 // SPDX-License-Identifier: GPL-2.0-only
  2 /*
  3  *  linux/fs/sysv/inode.c
  4  *
  5  *  minix/inode.c
  6  *  Copyright (C) 1991, 1992  Linus Torvalds
  7  *
  8  *  xenix/inode.c
  9  *  Copyright (C) 1992  Doug Evans
 10  *
 11  *  coh/inode.c
 12  *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 13  *
 14  *  sysv/inode.c
 15  *  Copyright (C) 1993  Paul B. Monday
 16  *
 17  *  sysv/inode.c
 18  *  Copyright (C) 1993  Bruno Haible
 19  *  Copyright (C) 1997, 1998  Krzysztof G. Baranowski
 20  *
 21  *  This file contains code for read/parsing the superblock.
 22  */
 23 
 24 #include <linux/module.h>
 25 #include <linux/init.h>
 26 #include <linux/slab.h>
 27 #include <linux/buffer_head.h>
 28 #include "sysv.h"
 29 
 30 /*
 31  * The following functions try to recognize specific filesystems.
 32  *
 33  * We recognize:
 34  * - Xenix FS by its magic number.
 35  * - SystemV FS by its magic number.
 36  * - Coherent FS by its funny fname/fpack field.
 37  * - SCO AFS by s_nfree == 0xffff
 38  * - V7 FS has no distinguishing features.
 39  *
 40  * We discriminate among SystemV4 and SystemV2 FS by the assumption that
 41  * the time stamp is not < 01-01-1980.
 42  */
 43 
 44 enum {
 45         JAN_1_1980 = (10*365 + 2) * 24 * 60 * 60
 46 };
 47 
 48 static void detected_xenix(struct sysv_sb_info *sbi, unsigned *max_links)
 49 {
 50         struct buffer_head *bh1 = sbi->s_bh1;
 51         struct buffer_head *bh2 = sbi->s_bh2;
 52         struct xenix_super_block * sbd1;
 53         struct xenix_super_block * sbd2;
 54 
 55         if (bh1 != bh2)
 56                 sbd1 = sbd2 = (struct xenix_super_block *) bh1->b_data;
 57         else {
 58                 /* block size = 512, so bh1 != bh2 */
 59                 sbd1 = (struct xenix_super_block *) bh1->b_data;
 60                 sbd2 = (struct xenix_super_block *) (bh2->b_data - 512);
 61         }
 62 
 63         *max_links = XENIX_LINK_MAX;
 64         sbi->s_fic_size = XENIX_NICINOD;
 65         sbi->s_flc_size = XENIX_NICFREE;
 66         sbi->s_sbd1 = (char *)sbd1;
 67         sbi->s_sbd2 = (char *)sbd2;
 68         sbi->s_sb_fic_count = &sbd1->s_ninode;
 69         sbi->s_sb_fic_inodes = &sbd1->s_inode[0];
 70         sbi->s_sb_total_free_inodes = &sbd2->s_tinode;
 71         sbi->s_bcache_count = &sbd1->s_nfree;
 72         sbi->s_bcache = &sbd1->s_free[0];
 73         sbi->s_free_blocks = &sbd2->s_tfree;
 74         sbi->s_sb_time = &sbd2->s_time;
 75         sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd1->s_isize);
 76         sbi->s_nzones = fs32_to_cpu(sbi, sbd1->s_fsize);
 77 }
 78 
 79 static void detected_sysv4(struct sysv_sb_info *sbi, unsigned *max_links)
 80 {
 81         struct sysv4_super_block * sbd;
 82         struct buffer_head *bh1 = sbi->s_bh1;
 83         struct buffer_head *bh2 = sbi->s_bh2;
 84 
 85         if (bh1 == bh2)
 86                 sbd = (struct sysv4_super_block *) (bh1->b_data + BLOCK_SIZE/2);
 87         else
 88                 sbd = (struct sysv4_super_block *) bh2->b_data;
 89 
 90         *max_links = SYSV_LINK_MAX;
 91         sbi->s_fic_size = SYSV_NICINOD;
 92         sbi->s_flc_size = SYSV_NICFREE;
 93         sbi->s_sbd1 = (char *)sbd;
 94         sbi->s_sbd2 = (char *)sbd;
 95         sbi->s_sb_fic_count = &sbd->s_ninode;
 96         sbi->s_sb_fic_inodes = &sbd->s_inode[0];
 97         sbi->s_sb_total_free_inodes = &sbd->s_tinode;
 98         sbi->s_bcache_count = &sbd->s_nfree;
 99         sbi->s_bcache = &sbd->s_free[0];
100         sbi->s_free_blocks = &sbd->s_tfree;
101         sbi->s_sb_time = &sbd->s_time;
102         sbi->s_sb_state = &sbd->s_state;
103         sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
104         sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
105 }
106 
107 static void detected_sysv2(struct sysv_sb_info *sbi, unsigned *max_links)
108 {
109         struct sysv2_super_block *sbd;
110         struct buffer_head *bh1 = sbi->s_bh1;
111         struct buffer_head *bh2 = sbi->s_bh2;
112 
113         if (bh1 == bh2)
114                 sbd = (struct sysv2_super_block *) (bh1->b_data + BLOCK_SIZE/2);
115         else
116                 sbd = (struct sysv2_super_block *) bh2->b_data;
117 
118         *max_links = SYSV_LINK_MAX;
119         sbi->s_fic_size = SYSV_NICINOD;
120         sbi->s_flc_size = SYSV_NICFREE;
121         sbi->s_sbd1 = (char *)sbd;
122         sbi->s_sbd2 = (char *)sbd;
123         sbi->s_sb_fic_count = &sbd->s_ninode;
124         sbi->s_sb_fic_inodes = &sbd->s_inode[0];
125         sbi->s_sb_total_free_inodes = &sbd->s_tinode;
126         sbi->s_bcache_count = &sbd->s_nfree;
127         sbi->s_bcache = &sbd->s_free[0];
128         sbi->s_free_blocks = &sbd->s_tfree;
129         sbi->s_sb_time = &sbd->s_time;
130         sbi->s_sb_state = &sbd->s_state;
131         sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
132         sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
133 }
134 
135 static void detected_coherent(struct sysv_sb_info *sbi, unsigned *max_links)
136 {
137         struct coh_super_block * sbd;
138         struct buffer_head *bh1 = sbi->s_bh1;
139 
140         sbd = (struct coh_super_block *) bh1->b_data;
141 
142         *max_links = COH_LINK_MAX;
143         sbi->s_fic_size = COH_NICINOD;
144         sbi->s_flc_size = COH_NICFREE;
145         sbi->s_sbd1 = (char *)sbd;
146         sbi->s_sbd2 = (char *)sbd;
147         sbi->s_sb_fic_count = &sbd->s_ninode;
148         sbi->s_sb_fic_inodes = &sbd->s_inode[0];
149         sbi->s_sb_total_free_inodes = &sbd->s_tinode;
150         sbi->s_bcache_count = &sbd->s_nfree;
151         sbi->s_bcache = &sbd->s_free[0];
152         sbi->s_free_blocks = &sbd->s_tfree;
153         sbi->s_sb_time = &sbd->s_time;
154         sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
155         sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
156 }
157 
158 static void detected_v7(struct sysv_sb_info *sbi, unsigned *max_links)
159 {
160         struct buffer_head *bh2 = sbi->s_bh2;
161         struct v7_super_block *sbd = (struct v7_super_block *)bh2->b_data;
162 
163         *max_links = V7_LINK_MAX;
164         sbi->s_fic_size = V7_NICINOD;
165         sbi->s_flc_size = V7_NICFREE;
166         sbi->s_sbd1 = (char *)sbd;
167         sbi->s_sbd2 = (char *)sbd;
168         sbi->s_sb_fic_count = &sbd->s_ninode;
169         sbi->s_sb_fic_inodes = &sbd->s_inode[0];
170         sbi->s_sb_total_free_inodes = &sbd->s_tinode;
171         sbi->s_bcache_count = &sbd->s_nfree;
172         sbi->s_bcache = &sbd->s_free[0];
173         sbi->s_free_blocks = &sbd->s_tfree;
174         sbi->s_sb_time = &sbd->s_time;
175         sbi->s_firstdatazone = fs16_to_cpu(sbi, sbd->s_isize);
176         sbi->s_nzones = fs32_to_cpu(sbi, sbd->s_fsize);
177 }
178 
179 static int detect_xenix(struct sysv_sb_info *sbi, struct buffer_head *bh)
180 {
181         struct xenix_super_block *sbd = (struct xenix_super_block *)bh->b_data;
182         if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0x2b5544))
183                 sbi->s_bytesex = BYTESEX_LE;
184         else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0x2b5544))
185                 sbi->s_bytesex = BYTESEX_BE;
186         else
187                 return 0;
188         switch (fs32_to_cpu(sbi, sbd->s_type)) {
189         case 1:
190                 sbi->s_type = FSTYPE_XENIX;
191                 return 1;
192         case 2:
193                 sbi->s_type = FSTYPE_XENIX;
194                 return 2;
195         default:
196                 return 0;
197         }
198 }
199 
200 static int detect_sysv(struct sysv_sb_info *sbi, struct buffer_head *bh)
201 {
202         struct super_block *sb = sbi->s_sb;
203         /* All relevant fields are at the same offsets in R2 and R4 */
204         struct sysv4_super_block * sbd;
205         u32 type;
206 
207         sbd = (struct sysv4_super_block *) (bh->b_data + BLOCK_SIZE/2);
208         if (*(__le32 *)&sbd->s_magic == cpu_to_le32(0xfd187e20))
209                 sbi->s_bytesex = BYTESEX_LE;
210         else if (*(__be32 *)&sbd->s_magic == cpu_to_be32(0xfd187e20))
211                 sbi->s_bytesex = BYTESEX_BE;
212         else
213                 return 0;
214 
215         type = fs32_to_cpu(sbi, sbd->s_type);
216  
217         if (fs16_to_cpu(sbi, sbd->s_nfree) == 0xffff) {
218                 sbi->s_type = FSTYPE_AFS;
219                 sbi->s_forced_ro = 1;
220                 if (!sb_rdonly(sb)) {
221                         printk("SysV FS: SCO EAFS on %s detected, " 
222                                 "forcing read-only mode.\n", 
223                                 sb->s_id);
224                 }
225                 return type;
226         }
227  
228         if (fs32_to_cpu(sbi, sbd->s_time) < JAN_1_1980) {
229                 /* this is likely to happen on SystemV2 FS */
230                 if (type > 3 || type < 1)
231                         return 0;
232                 sbi->s_type = FSTYPE_SYSV2;
233                 return type;
234         }
235         if ((type > 3 || type < 1) && (type > 0x30 || type < 0x10))
236                 return 0;
237 
238         /* On Interactive Unix (ISC) Version 4.0/3.x s_type field = 0x10,
239            0x20 or 0x30 indicates that symbolic links and the 14-character
240            filename limit is gone. Due to lack of information about this
241            feature read-only mode seems to be a reasonable approach... -KGB */
242 
243         if (type >= 0x10) {
244                 printk("SysV FS: can't handle long file names on %s, "
245                        "forcing read-only mode.\n", sb->s_id);
246                 sbi->s_forced_ro = 1;
247         }
248 
249         sbi->s_type = FSTYPE_SYSV4;
250         return type >= 0x10 ? type >> 4 : type;
251 }
252 
253 static int detect_coherent(struct sysv_sb_info *sbi, struct buffer_head *bh)
254 {
255         struct coh_super_block * sbd;
256 
257         sbd = (struct coh_super_block *) (bh->b_data + BLOCK_SIZE/2);
258         if ((memcmp(sbd->s_fname,"noname",6) && memcmp(sbd->s_fname,"xxxxx ",6))
259             || (memcmp(sbd->s_fpack,"nopack",6) && memcmp(sbd->s_fpack,"xxxxx\n",6)))
260                 return 0;
261         sbi->s_bytesex = BYTESEX_PDP;
262         sbi->s_type = FSTYPE_COH;
263         return 1;
264 }
265 
266 static int detect_sysv_odd(struct sysv_sb_info *sbi, struct buffer_head *bh)
267 {
268         int size = detect_sysv(sbi, bh);
269 
270         return size>2 ? 0 : size;
271 }
272 
273 static struct {
274         int block;
275         int (*test)(struct sysv_sb_info *, struct buffer_head *);
276 } flavours[] = {
277         {1, detect_xenix},
278         {0, detect_sysv},
279         {0, detect_coherent},
280         {9, detect_sysv_odd},
281         {15,detect_sysv_odd},
282         {18,detect_sysv},
283 };
284 
285 static char *flavour_names[] = {
286         [FSTYPE_XENIX]  = "Xenix",
287         [FSTYPE_SYSV4]  = "SystemV",
288         [FSTYPE_SYSV2]  = "SystemV Release 2",
289         [FSTYPE_COH]    = "Coherent",
290         [FSTYPE_V7]     = "V7",
291         [FSTYPE_AFS]    = "AFS",
292 };
293 
294 static void (*flavour_setup[])(struct sysv_sb_info *, unsigned *) = {
295         [FSTYPE_XENIX]  = detected_xenix,
296         [FSTYPE_SYSV4]  = detected_sysv4,
297         [FSTYPE_SYSV2]  = detected_sysv2,
298         [FSTYPE_COH]    = detected_coherent,
299         [FSTYPE_V7]     = detected_v7,
300         [FSTYPE_AFS]    = detected_sysv4,
301 };
302 
303 static int complete_read_super(struct super_block *sb, int silent, int size)
304 {
305         struct sysv_sb_info *sbi = SYSV_SB(sb);
306         struct inode *root_inode;
307         char *found = flavour_names[sbi->s_type];
308         u_char n_bits = size+8;
309         int bsize = 1 << n_bits;
310         int bsize_4 = bsize >> 2;
311 
312         sbi->s_firstinodezone = 2;
313 
314         flavour_setup[sbi->s_type](sbi, &sb->s_max_links);
315         
316         sbi->s_ndatazones = sbi->s_nzones - sbi->s_firstdatazone;
317         sbi->s_inodes_per_block = bsize >> 6;
318         sbi->s_inodes_per_block_1 = (bsize >> 6)-1;
319         sbi->s_inodes_per_block_bits = n_bits-6;
320         sbi->s_ind_per_block = bsize_4;
321         sbi->s_ind_per_block_2 = bsize_4*bsize_4;
322         sbi->s_toobig_block = 10 + bsize_4 * (1 + bsize_4 * (1 + bsize_4));
323         sbi->s_ind_per_block_bits = n_bits-2;
324 
325         sbi->s_ninodes = (sbi->s_firstdatazone - sbi->s_firstinodezone)
326                 << sbi->s_inodes_per_block_bits;
327 
328         if (!silent)
329                 printk("VFS: Found a %s FS (block size = %ld) on device %s\n",
330                        found, sb->s_blocksize, sb->s_id);
331 
332         sb->s_magic = SYSV_MAGIC_BASE + sbi->s_type;
333         /* set up enough so that it can read an inode */
334         sb->s_op = &sysv_sops;
335         if (sbi->s_forced_ro)
336                 sb->s_flags |= SB_RDONLY;
337         root_inode = sysv_iget(sb, SYSV_ROOT_INO);
338         if (IS_ERR(root_inode)) {
339                 printk("SysV FS: get root inode failed\n");
340                 return 0;
341         }
342         sb->s_root = d_make_root(root_inode);
343         if (!sb->s_root) {
344                 printk("SysV FS: get root dentry failed\n");
345                 return 0;
346         }
347         return 1;
348 }
349 
350 static int sysv_fill_super(struct super_block *sb, void *data, int silent)
351 {
352         struct buffer_head *bh1, *bh = NULL;
353         struct sysv_sb_info *sbi;
354         unsigned long blocknr;
355         int size = 0, i;
356         
357         BUILD_BUG_ON(1024 != sizeof (struct xenix_super_block));
358         BUILD_BUG_ON(512 != sizeof (struct sysv4_super_block));
359         BUILD_BUG_ON(512 != sizeof (struct sysv2_super_block));
360         BUILD_BUG_ON(500 != sizeof (struct coh_super_block));
361         BUILD_BUG_ON(64 != sizeof (struct sysv_inode));
362 
363         sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
364         if (!sbi)
365                 return -ENOMEM;
366 
367         sbi->s_sb = sb;
368         sbi->s_block_base = 0;
369         mutex_init(&sbi->s_lock);
370         sb->s_fs_info = sbi;
371         sb->s_time_min = 0;
372         sb->s_time_max = U32_MAX;
373         sb_set_blocksize(sb, BLOCK_SIZE);
374 
375         for (i = 0; i < ARRAY_SIZE(flavours) && !size; i++) {
376                 brelse(bh);
377                 bh = sb_bread(sb, flavours[i].block);
378                 if (!bh)
379                         continue;
380                 size = flavours[i].test(SYSV_SB(sb), bh);
381         }
382 
383         if (!size)
384                 goto Eunknown;
385 
386         switch (size) {
387                 case 1:
388                         blocknr = bh->b_blocknr << 1;
389                         brelse(bh);
390                         sb_set_blocksize(sb, 512);
391                         bh1 = sb_bread(sb, blocknr);
392                         bh = sb_bread(sb, blocknr + 1);
393                         break;
394                 case 2:
395                         bh1 = bh;
396                         break;
397                 case 3:
398                         blocknr = bh->b_blocknr >> 1;
399                         brelse(bh);
400                         sb_set_blocksize(sb, 2048);
401                         bh1 = bh = sb_bread(sb, blocknr);
402                         break;
403                 default:
404                         goto Ebadsize;
405         }
406 
407         if (bh && bh1) {
408                 sbi->s_bh1 = bh1;
409                 sbi->s_bh2 = bh;
410                 if (complete_read_super(sb, silent, size))
411                         return 0;
412         }
413 
414         brelse(bh1);
415         brelse(bh);
416         sb_set_blocksize(sb, BLOCK_SIZE);
417         printk("oldfs: cannot read superblock\n");
418 failed:
419         kfree(sbi);
420         return -EINVAL;
421 
422 Eunknown:
423         brelse(bh);
424         if (!silent)
425                 printk("VFS: unable to find oldfs superblock on device %s\n",
426                         sb->s_id);
427         goto failed;
428 Ebadsize:
429         brelse(bh);
430         if (!silent)
431                 printk("VFS: oldfs: unsupported block size (%dKb)\n",
432                         1<<(size-2));
433         goto failed;
434 }
435 
436 static int v7_sanity_check(struct super_block *sb, struct buffer_head *bh)
437 {
438         struct v7_super_block *v7sb;
439         struct sysv_inode *v7i;
440         struct buffer_head *bh2;
441         struct sysv_sb_info *sbi;
442 
443         sbi = sb->s_fs_info;
444 
445         /* plausibility check on superblock */
446         v7sb = (struct v7_super_block *) bh->b_data;
447         if (fs16_to_cpu(sbi, v7sb->s_nfree) > V7_NICFREE ||
448             fs16_to_cpu(sbi, v7sb->s_ninode) > V7_NICINOD ||
449             fs32_to_cpu(sbi, v7sb->s_fsize) > V7_MAXSIZE)
450                 return 0;
451 
452         /* plausibility check on root inode: it is a directory,
453            with a nonzero size that is a multiple of 16 */
454         bh2 = sb_bread(sb, 2);
455         if (bh2 == NULL)
456                 return 0;
457 
458         v7i = (struct sysv_inode *)(bh2->b_data + 64);
459         if ((fs16_to_cpu(sbi, v7i->i_mode) & ~0777) != S_IFDIR ||
460             (fs32_to_cpu(sbi, v7i->i_size) == 0) ||
461             (fs32_to_cpu(sbi, v7i->i_size) & 017) ||
462             (fs32_to_cpu(sbi, v7i->i_size) > V7_NFILES *
463              sizeof(struct sysv_dir_entry))) {
464                 brelse(bh2);
465                 return 0;
466         }
467 
468         brelse(bh2);
469         return 1;
470 }
471 
472 static int v7_fill_super(struct super_block *sb, void *data, int silent)
473 {
474         struct sysv_sb_info *sbi;
475         struct buffer_head *bh;
476 
477         if (440 != sizeof (struct v7_super_block))
478                 panic("V7 FS: bad super-block size");
479         if (64 != sizeof (struct sysv_inode))
480                 panic("sysv fs: bad i-node size");
481 
482         sbi = kzalloc(sizeof(struct sysv_sb_info), GFP_KERNEL);
483         if (!sbi)
484                 return -ENOMEM;
485 
486         sbi->s_sb = sb;
487         sbi->s_block_base = 0;
488         sbi->s_type = FSTYPE_V7;
489         mutex_init(&sbi->s_lock);
490         sb->s_fs_info = sbi;
491         sb->s_time_min = 0;
492         sb->s_time_max = U32_MAX;
493         
494         sb_set_blocksize(sb, 512);
495 
496         if ((bh = sb_bread(sb, 1)) == NULL) {
497                 if (!silent)
498                         printk("VFS: unable to read V7 FS superblock on "
499                                "device %s.\n", sb->s_id);
500                 goto failed;
501         }
502 
503         /* Try PDP-11 UNIX */
504         sbi->s_bytesex = BYTESEX_PDP;
505         if (v7_sanity_check(sb, bh))
506                 goto detected;
507 
508         /* Try PC/IX, v7/x86 */
509         sbi->s_bytesex = BYTESEX_LE;
510         if (v7_sanity_check(sb, bh))
511                 goto detected;
512 
513         goto failed;
514 
515 detected:
516         sbi->s_bh1 = bh;
517         sbi->s_bh2 = bh;
518         if (complete_read_super(sb, silent, 1))
519                 return 0;
520 
521 failed:
522         printk(KERN_ERR "VFS: could not find a valid V7 on %s.\n",
523                 sb->s_id);
524         brelse(bh);
525         kfree(sbi);
526         return -EINVAL;
527 }
528 
529 /* Every kernel module contains stuff like this. */
530 
531 static struct dentry *sysv_mount(struct file_system_type *fs_type,
532         int flags, const char *dev_name, void *data)
533 {
534         return mount_bdev(fs_type, flags, dev_name, data, sysv_fill_super);
535 }
536 
537 static struct dentry *v7_mount(struct file_system_type *fs_type,
538         int flags, const char *dev_name, void *data)
539 {
540         return mount_bdev(fs_type, flags, dev_name, data, v7_fill_super);
541 }
542 
543 static struct file_system_type sysv_fs_type = {
544         .owner          = THIS_MODULE,
545         .name           = "sysv",
546         .mount          = sysv_mount,
547         .kill_sb        = kill_block_super,
548         .fs_flags       = FS_REQUIRES_DEV,
549 };
550 MODULE_ALIAS_FS("sysv");
551 
552 static struct file_system_type v7_fs_type = {
553         .owner          = THIS_MODULE,
554         .name           = "v7",
555         .mount          = v7_mount,
556         .kill_sb        = kill_block_super,
557         .fs_flags       = FS_REQUIRES_DEV,
558 };
559 MODULE_ALIAS_FS("v7");
560 MODULE_ALIAS("v7");
561 
562 static int __init init_sysv_fs(void)
563 {
564         int error;
565 
566         error = sysv_init_icache();
567         if (error)
568                 goto out;
569         error = register_filesystem(&sysv_fs_type);
570         if (error)
571                 goto destroy_icache;
572         error = register_filesystem(&v7_fs_type);
573         if (error)
574                 goto unregister;
575         return 0;
576 
577 unregister:
578         unregister_filesystem(&sysv_fs_type);
579 destroy_icache:
580         sysv_destroy_icache();
581 out:
582         return error;
583 }
584 
585 static void __exit exit_sysv_fs(void)
586 {
587         unregister_filesystem(&sysv_fs_type);
588         unregister_filesystem(&v7_fs_type);
589         sysv_destroy_icache();
590 }
591 
592 module_init(init_sysv_fs)
593 module_exit(exit_sysv_fs)
594 MODULE_LICENSE("GPL");
595 

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