fs/adfs/dir_f.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/adfs/dir_f.c
   4  *
   5  * Copyright (C) 1997-1999 Russell King
   6  *
   7  *  E and F format directory handling
   8  */
   9 #include "adfs.h"
  10 #include "dir_f.h"
  11
  12 static void adfs_f_free(struct adfs_dir *dir);
  13
  14 /*
  15  * Read an (unaligned) value of length 1..4 bytes
  16  */
  17 static inline unsigned int adfs_readval(unsigned char *p, int len)
  18 {
  19         unsigned int val = 0;
  20
  21         switch (len) {
  22         case 4:         val |= p[3] << 24;
  23                         /* fall through */
  24         case 3:         val |= p[2] << 16;
  25                         /* fall through */
  26         case 2:         val |= p[1] << 8;
  27                         /* fall through */
  28         default:        val |= p[0];
  29         }
  30         return val;
  31 }
  32
  33 static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
  34 {
  35         switch (len) {
  36         case 4:         p[3] = val >> 24;
  37                         /* fall through */
  38         case 3:         p[2] = val >> 16;
  39                         /* fall through */
  40         case 2:         p[1] = val >> 8;
  41                         /* fall through */
  42         default:        p[0] = val;
  43         }
  44 }
  45
  46 #define ror13(v) ((v >> 13) | (v << 19))
  47
  48 #define dir_u8(idx)                             \
  49         ({ int _buf = idx >> blocksize_bits;    \
  50            int _off = idx - (_buf << blocksize_bits);\
  51           *(u8 *)(bh[_buf]->b_data + _off);     \
  52         })
  53
  54 #define dir_u32(idx)                            \
  55         ({ int _buf = idx >> blocksize_bits;    \
  56            int _off = idx - (_buf << blocksize_bits);\
  57           *(__le32 *)(bh[_buf]->b_data + _off); \
  58         })
  59
  60 #define bufoff(_bh,_idx)                        \
  61         ({ int _buf = _idx >> blocksize_bits;   \
  62            int _off = _idx - (_buf << blocksize_bits);\
  63           (u8 *)(_bh[_buf]->b_data + _off);     \
  64         })
  65
  66 /*
  67  * There are some algorithms that are nice in
  68  * assembler, but a bitch in C...  This is one
  69  * of them.
  70  */
  71 static u8
  72 adfs_dir_checkbyte(const struct adfs_dir *dir)
  73 {
  74         struct buffer_head * const *bh = dir->bh;
  75         const int blocksize_bits = dir->sb->s_blocksize_bits;
  76         union { __le32 *ptr32; u8 *ptr8; } ptr, end;
  77         u32 dircheck = 0;
  78         int last = 5 - 26;
  79         int i = 0;
  80
  81         /*
  82          * Accumulate each word up to the last whole
  83          * word of the last directory entry.  This
  84          * can spread across several buffer heads.
  85          */
  86         do {
  87                 last += 26;
  88                 do {
  89                         dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);
  90
  91                         i += sizeof(u32);
  92                 } while (i < (last & ~3));
  93         } while (dir_u8(last) != 0);
  94
  95         /*
  96          * Accumulate the last few bytes.  These
  97          * bytes will be within the same bh.
  98          */
  99         if (i != last) {
 100                 ptr.ptr8 = bufoff(bh, i);
 101                 end.ptr8 = ptr.ptr8 + last - i;
 102
 103                 do {
 104                         dircheck = *ptr.ptr8++ ^ ror13(dircheck);
 105                 } while (ptr.ptr8 < end.ptr8);
 106         }
 107
 108         /*
 109          * The directory tail is in the final bh
 110          * Note that contary to the RISC OS PRMs,
 111          * the first few bytes are NOT included
 112          * in the check.  All bytes are in the
 113          * same bh.
 114          */
 115         ptr.ptr8 = bufoff(bh, 2008);
 116         end.ptr8 = ptr.ptr8 + 36;
 117
 118         do {
 119                 __le32 v = *ptr.ptr32++;
 120                 dircheck = le32_to_cpu(v) ^ ror13(dircheck);
 121         } while (ptr.ptr32 < end.ptr32);
 122
 123         return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
 124 }
 125
 126 /* Read and check that a directory is valid */
 127 static int adfs_dir_read(struct super_block *sb, u32 indaddr,
 128                          unsigned int size, struct adfs_dir *dir)
 129 {
 130         const unsigned int blocksize_bits = sb->s_blocksize_bits;
 131         int blk = 0;
 132
 133         /*
 134          * Directories which are not a multiple of 2048 bytes
 135          * are considered bad v2 [3.6]
 136          */
 137         if (size & 2047)
 138                 goto bad_dir;
 139
 140         size >>= blocksize_bits;
 141
 142         dir->nr_buffers = 0;
 143         dir->sb = sb;
 144
 145         for (blk = 0; blk < size; blk++) {
 146                 int phys;
 147
 148                 phys = __adfs_block_map(sb, indaddr, blk);
 149                 if (!phys) {
 150                         adfs_error(sb, "dir %06x has a hole at offset %d",
 151                                    indaddr, blk);
 152                         goto release_buffers;
 153                 }
 154
 155                 dir->bh[blk] = sb_bread(sb, phys);
 156                 if (!dir->bh[blk])
 157                         goto release_buffers;
 158         }
 159
 160         memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
 161         memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
 162
 163         if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
 164             memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
 165                 goto bad_dir;
 166
 167         if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
 168             memcmp(&dir->dirhead.startname, "Hugo", 4))
 169                 goto bad_dir;
 170
 171         if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
 172                 goto bad_dir;
 173
 174         dir->nr_buffers = blk;
 175
 176         return 0;
 177
 178 bad_dir:
 179         adfs_error(sb, "dir %06x is corrupted", indaddr);
 180 release_buffers:
 181         for (blk -= 1; blk >= 0; blk -= 1)
 182                 brelse(dir->bh[blk]);
 183
 184         dir->sb = NULL;
 185
 186         return -EIO;
 187 }
 188
 189 /*
 190  * convert a disk-based directory entry to a Linux ADFS directory entry
 191  */
 192 static inline void
 193 adfs_dir2obj(struct adfs_dir *dir, struct object_info *obj,
 194         struct adfs_direntry *de)
 195 {
 196         unsigned int name_len;
 197
 198         for (name_len = 0; name_len < ADFS_F_NAME_LEN; name_len++) {
 199                 if (de->dirobname[name_len] < ' ')
 200                         break;
 201
 202                 obj->name[name_len] = de->dirobname[name_len];
 203         }
 204
 205         obj->name_len = name_len;
 206         obj->indaddr  = adfs_readval(de->dirinddiscadd, 3);
 207         obj->loadaddr = adfs_readval(de->dirload, 4);
 208         obj->execaddr = adfs_readval(de->direxec, 4);
 209         obj->size     = adfs_readval(de->dirlen,  4);
 210         obj->attr     = de->newdiratts;
 211
 212         adfs_object_fixup(dir, obj);
 213 }
 214
 215 /*
 216  * convert a Linux ADFS directory entry to a disk-based directory entry
 217  */
 218 static inline void
 219 adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
 220 {
 221         adfs_writeval(de->dirinddiscadd, 3, obj->indaddr);
 222         adfs_writeval(de->dirload, 4, obj->loadaddr);
 223         adfs_writeval(de->direxec, 4, obj->execaddr);
 224         adfs_writeval(de->dirlen,  4, obj->size);
 225         de->newdiratts = obj->attr;
 226 }
 227
 228 /*
 229  * get a directory entry.  Note that the caller is responsible
 230  * for holding the relevant locks.
 231  */
 232 static int
 233 __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
 234 {
 235         struct super_block *sb = dir->sb;
 236         struct adfs_direntry de;
 237         int thissize, buffer, offset;
 238
 239         buffer = pos >> sb->s_blocksize_bits;
 240
 241         if (buffer > dir->nr_buffers)
 242                 return -EINVAL;
 243
 244         offset = pos & (sb->s_blocksize - 1);
 245         thissize = sb->s_blocksize - offset;
 246         if (thissize > 26)
 247                 thissize = 26;
 248
 249         memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
 250         if (thissize != 26)
 251                 memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
 252                        26 - thissize);
 253
 254         if (!de.dirobname[0])
 255                 return -ENOENT;
 256
 257         adfs_dir2obj(dir, obj, &de);
 258
 259         return 0;
 260 }
 261
 262 static int
 263 __adfs_dir_put(struct adfs_dir *dir, int pos, struct object_info *obj)
 264 {
 265         struct super_block *sb = dir->sb;
 266         struct adfs_direntry de;
 267         int thissize, buffer, offset;
 268
 269         buffer = pos >> sb->s_blocksize_bits;
 270
 271         if (buffer > dir->nr_buffers)
 272                 return -EINVAL;
 273
 274         offset = pos & (sb->s_blocksize - 1);
 275         thissize = sb->s_blocksize - offset;
 276         if (thissize > 26)
 277                 thissize = 26;
 278
 279         /*
 280          * Get the entry in total
 281          */
 282         memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
 283         if (thissize != 26)
 284                 memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
 285                        26 - thissize);
 286
 287         /*
 288          * update it
 289          */
 290         adfs_obj2dir(&de, obj);
 291
 292         /*
 293          * Put the new entry back
 294          */
 295         memcpy(dir->bh[buffer]->b_data + offset, &de, thissize);
 296         if (thissize != 26)
 297                 memcpy(dir->bh[buffer + 1]->b_data, ((char *)&de) + thissize,
 298                        26 - thissize);
 299
 300         return 0;
 301 }
 302
 303 /*
 304  * the caller is responsible for holding the necessary
 305  * locks.
 306  */
 307 static int adfs_dir_find_entry(struct adfs_dir *dir, u32 indaddr)
 308 {
 309         int pos, ret;
 310
 311         ret = -ENOENT;
 312
 313         for (pos = 5; pos < ADFS_NUM_DIR_ENTRIES * 26 + 5; pos += 26) {
 314                 struct object_info obj;
 315
 316                 if (!__adfs_dir_get(dir, pos, &obj))
 317                         break;
 318
 319                 if (obj.indaddr == indaddr) {
 320                         ret = pos;
 321                         break;
 322                 }
 323         }
 324
 325         return ret;
 326 }
 327
 328 static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
 329                        struct adfs_dir *dir)
 330 {
 331         int ret;
 332
 333         if (size != ADFS_NEWDIR_SIZE)
 334                 return -EIO;
 335
 336         ret = adfs_dir_read(sb, indaddr, size, dir);
 337         if (ret)
 338                 adfs_error(sb, "unable to read directory");
 339         else
 340                 dir->parent_id = adfs_readval(dir->dirtail.new.dirparent, 3);
 341
 342         return ret;
 343 }
 344
 345 static int
 346 adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
 347 {
 348         if (fpos >= ADFS_NUM_DIR_ENTRIES)
 349                 return -ENOENT;
 350
 351         dir->pos = 5 + fpos * 26;
 352         return 0;
 353 }
 354
 355 static int
 356 adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
 357 {
 358         unsigned int ret;
 359
 360         ret = __adfs_dir_get(dir, dir->pos, obj);
 361         if (ret == 0)
 362                 dir->pos += 26;
 363
 364         return ret;
 365 }
 366
 367 static int
 368 adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
 369 {
 370         struct super_block *sb = dir->sb;
 371         int ret, i;
 372
 373         ret = adfs_dir_find_entry(dir, obj->indaddr);
 374         if (ret < 0) {
 375                 adfs_error(dir->sb, "unable to locate entry to update");
 376                 goto out;
 377         }
 378
 379         __adfs_dir_put(dir, ret, obj);
 380
 381         /*
 382          * Increment directory sequence number
 383          */
 384         dir->bh[0]->b_data[0] += 1;
 385         dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 6] += 1;
 386
 387         ret = adfs_dir_checkbyte(dir);
 388         /*
 389          * Update directory check byte
 390          */
 391         dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 1] = ret;
 392
 393 #if 1
 394         {
 395         const unsigned int blocksize_bits = sb->s_blocksize_bits;
 396
 397         memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
 398         memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
 399
 400         if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
 401             memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
 402                 goto bad_dir;
 403
 404         if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
 405             memcmp(&dir->dirhead.startname, "Hugo", 4))
 406                 goto bad_dir;
 407
 408         if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
 409                 goto bad_dir;
 410         }
 411 #endif
 412         for (i = dir->nr_buffers - 1; i >= 0; i--)
 413                 mark_buffer_dirty(dir->bh[i]);
 414
 415         ret = 0;
 416 out:
 417         return ret;
 418 #if 1
 419 bad_dir:
 420         adfs_error(dir->sb, "whoops!  I broke a directory!");
 421         return -EIO;
 422 #endif
 423 }
 424
 425 static int
 426 adfs_f_sync(struct adfs_dir *dir)
 427 {
 428         int err = 0;
 429         int i;
 430
 431         for (i = dir->nr_buffers - 1; i >= 0; i--) {
 432                 struct buffer_head *bh = dir->bh[i];
 433                 sync_dirty_buffer(bh);
 434                 if (buffer_req(bh) && !buffer_uptodate(bh))
 435                         err = -EIO;
 436         }
 437
 438         return err;
 439 }
 440
 441 static void
 442 adfs_f_free(struct adfs_dir *dir)
 443 {
 444         int i;
 445
 446         for (i = dir->nr_buffers - 1; i >= 0; i--) {
 447                 brelse(dir->bh[i]);
 448                 dir->bh[i] = NULL;
 449         }
 450
 451         dir->nr_buffers = 0;
 452         dir->sb = NULL;
 453 }
 454
 455 const struct adfs_dir_ops adfs_f_dir_ops = {
 456         .read           = adfs_f_read,
 457         .setpos         = adfs_f_setpos,
 458         .getnext        = adfs_f_getnext,
 459         .update         = adfs_f_update,
 460         .sync           = adfs_f_sync,
 461         .free           = adfs_f_free
 462 };