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 /*
  13  * Read an (unaligned) value of length 1..4 bytes
  14  */
  15 static inline unsigned int adfs_readval(unsigned char *p, int len)
  16 {
  17         unsigned int val = 0;
  18
  19         switch (len) {
  20         case 4:         val |= p[3] << 24;
  21                 fallthrough;
  22         case 3:         val |= p[2] << 16;
  23                 fallthrough;
  24         case 2:         val |= p[1] << 8;
  25                 fallthrough;
  26         default:        val |= p[0];
  27         }
  28         return val;
  29 }
  30
  31 static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
  32 {
  33         switch (len) {
  34         case 4:         p[3] = val >> 24;
  35                 fallthrough;
  36         case 3:         p[2] = val >> 16;
  37                 fallthrough;
  38         case 2:         p[1] = val >> 8;
  39                 fallthrough;
  40         default:        p[0] = val;
  41         }
  42 }
  43
  44 #define ror13(v) ((v >> 13) | (v << 19))
  45
  46 #define dir_u8(idx)                             \
  47         ({ int _buf = idx >> blocksize_bits;    \
  48            int _off = idx - (_buf << blocksize_bits);\
  49           *(u8 *)(bh[_buf]->b_data + _off);     \
  50         })
  51
  52 #define dir_u32(idx)                            \
  53         ({ int _buf = idx >> blocksize_bits;    \
  54            int _off = idx - (_buf << blocksize_bits);\
  55           *(__le32 *)(bh[_buf]->b_data + _off); \
  56         })
  57
  58 #define bufoff(_bh,_idx)                        \
  59         ({ int _buf = _idx >> blocksize_bits;   \
  60            int _off = _idx - (_buf << blocksize_bits);\
  61           (void *)(_bh[_buf]->b_data + _off);   \
  62         })
  63
  64 /*
  65  * There are some algorithms that are nice in
  66  * assembler, but a bitch in C...  This is one
  67  * of them.
  68  */
  69 static u8
  70 adfs_dir_checkbyte(const struct adfs_dir *dir)
  71 {
  72         struct buffer_head * const *bh = dir->bh;
  73         const int blocksize_bits = dir->sb->s_blocksize_bits;
  74         union { __le32 *ptr32; u8 *ptr8; } ptr, end;
  75         u32 dircheck = 0;
  76         int last = 5 - 26;
  77         int i = 0;
  78
  79         /*
  80          * Accumulate each word up to the last whole
  81          * word of the last directory entry.  This
  82          * can spread across several buffer heads.
  83          */
  84         do {
  85                 last += 26;
  86                 do {
  87                         dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);
  88
  89                         i += sizeof(u32);
  90                 } while (i < (last & ~3));
  91         } while (dir_u8(last) != 0);
  92
  93         /*
  94          * Accumulate the last few bytes.  These
  95          * bytes will be within the same bh.
  96          */
  97         if (i != last) {
  98                 ptr.ptr8 = bufoff(bh, i);
  99                 end.ptr8 = ptr.ptr8 + last - i;
 100
 101                 do {
 102                         dircheck = *ptr.ptr8++ ^ ror13(dircheck);
 103                 } while (ptr.ptr8 < end.ptr8);
 104         }
 105
 106         /*
 107          * The directory tail is in the final bh
 108          * Note that contary to the RISC OS PRMs,
 109          * the first few bytes are NOT included
 110          * in the check.  All bytes are in the
 111          * same bh.
 112          */
 113         ptr.ptr8 = bufoff(bh, 2008);
 114         end.ptr8 = ptr.ptr8 + 36;
 115
 116         do {
 117                 __le32 v = *ptr.ptr32++;
 118                 dircheck = le32_to_cpu(v) ^ ror13(dircheck);
 119         } while (ptr.ptr32 < end.ptr32);
 120
 121         return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
 122 }
 123
 124 static int adfs_f_validate(struct adfs_dir *dir)
 125 {
 126         struct adfs_dirheader *head = dir->dirhead;
 127         struct adfs_newdirtail *tail = dir->newtail;
 128
 129         if (head->startmasseq != tail->endmasseq ||
 130             tail->dirlastmask || tail->reserved[0] || tail->reserved[1] ||
 131             (memcmp(&head->startname, "Nick", 4) &&
 132              memcmp(&head->startname, "Hugo", 4)) ||
 133             memcmp(&head->startname, &tail->endname, 4) ||
 134             adfs_dir_checkbyte(dir) != tail->dircheckbyte)
 135                 return -EIO;
 136
 137         return 0;
 138 }
 139
 140 /* Read and check that a directory is valid */
 141 static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
 142                        struct adfs_dir *dir)
 143 {
 144         const unsigned int blocksize_bits = sb->s_blocksize_bits;
 145         int ret;
 146
 147         if (size && size != ADFS_NEWDIR_SIZE)
 148                 return -EIO;
 149
 150         ret = adfs_dir_read_buffers(sb, indaddr, ADFS_NEWDIR_SIZE, dir);
 151         if (ret)
 152                 return ret;
 153
 154         dir->dirhead = bufoff(dir->bh, 0);
 155         dir->newtail = bufoff(dir->bh, 2007);
 156
 157         if (adfs_f_validate(dir))
 158                 goto bad_dir;
 159
 160         dir->parent_id = adfs_readval(dir->newtail->dirparent, 3);
 161
 162         return 0;
 163
 164 bad_dir:
 165         adfs_error(sb, "dir %06x is corrupted", indaddr);
 166         adfs_dir_relse(dir);
 167
 168         return -EIO;
 169 }
 170
 171 /*
 172  * convert a disk-based directory entry to a Linux ADFS directory entry
 173  */
 174 static inline void
 175 adfs_dir2obj(struct adfs_dir *dir, struct object_info *obj,
 176         struct adfs_direntry *de)
 177 {
 178         unsigned int name_len;
 179
 180         for (name_len = 0; name_len < ADFS_F_NAME_LEN; name_len++) {
 181                 if (de->dirobname[name_len] < ' ')
 182                         break;
 183
 184                 obj->name[name_len] = de->dirobname[name_len];
 185         }
 186
 187         obj->name_len = name_len;
 188         obj->indaddr  = adfs_readval(de->dirinddiscadd, 3);
 189         obj->loadaddr = adfs_readval(de->dirload, 4);
 190         obj->execaddr = adfs_readval(de->direxec, 4);
 191         obj->size     = adfs_readval(de->dirlen,  4);
 192         obj->attr     = de->newdiratts;
 193
 194         adfs_object_fixup(dir, obj);
 195 }
 196
 197 /*
 198  * convert a Linux ADFS directory entry to a disk-based directory entry
 199  */
 200 static inline void
 201 adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
 202 {
 203         adfs_writeval(de->dirinddiscadd, 3, obj->indaddr);
 204         adfs_writeval(de->dirload, 4, obj->loadaddr);
 205         adfs_writeval(de->direxec, 4, obj->execaddr);
 206         adfs_writeval(de->dirlen,  4, obj->size);
 207         de->newdiratts = obj->attr;
 208 }
 209
 210 /*
 211  * get a directory entry.  Note that the caller is responsible
 212  * for holding the relevant locks.
 213  */
 214 static int
 215 __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
 216 {
 217         struct adfs_direntry de;
 218         int ret;
 219
 220         ret = adfs_dir_copyfrom(&de, dir, pos, 26);
 221         if (ret)
 222                 return ret;
 223
 224         if (!de.dirobname[0])
 225                 return -ENOENT;
 226
 227         adfs_dir2obj(dir, obj, &de);
 228
 229         return 0;
 230 }
 231
 232 static int
 233 adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
 234 {
 235         if (fpos >= ADFS_NUM_DIR_ENTRIES)
 236                 return -ENOENT;
 237
 238         dir->pos = 5 + fpos * 26;
 239         return 0;
 240 }
 241
 242 static int
 243 adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
 244 {
 245         unsigned int ret;
 246
 247         ret = __adfs_dir_get(dir, dir->pos, obj);
 248         if (ret == 0)
 249                 dir->pos += 26;
 250
 251         return ret;
 252 }
 253
 254 static int adfs_f_iterate(struct adfs_dir *dir, struct dir_context *ctx)
 255 {
 256         struct object_info obj;
 257         int pos = 5 + (ctx->pos - 2) * 26;
 258
 259         while (ctx->pos < 2 + ADFS_NUM_DIR_ENTRIES) {
 260                 if (__adfs_dir_get(dir, pos, &obj))
 261                         break;
 262                 if (!dir_emit(ctx, obj.name, obj.name_len,
 263                               obj.indaddr, DT_UNKNOWN))
 264                         break;
 265                 pos += 26;
 266                 ctx->pos++;
 267         }
 268         return 0;
 269 }
 270
 271 static int adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
 272 {
 273         struct adfs_direntry de;
 274         int offset, ret;
 275
 276         offset = 5 - (int)sizeof(de);
 277
 278         do {
 279                 offset += sizeof(de);
 280                 ret = adfs_dir_copyfrom(&de, dir, offset, sizeof(de));
 281                 if (ret) {
 282                         adfs_error(dir->sb, "error reading directory entry");
 283                         return -ENOENT;
 284                 }
 285                 if (!de.dirobname[0]) {
 286                         adfs_error(dir->sb, "unable to locate entry to update");
 287                         return -ENOENT;
 288                 }
 289         } while (adfs_readval(de.dirinddiscadd, 3) != obj->indaddr);
 290
 291         /* Update the directory entry with the new object state */
 292         adfs_obj2dir(&de, obj);
 293
 294         /* Write the directory entry back to the directory */
 295         return adfs_dir_copyto(dir, offset, &de, 26);
 296 }
 297
 298 static int adfs_f_commit(struct adfs_dir *dir)
 299 {
 300         int ret;
 301
 302         /* Increment directory sequence number */
 303         dir->dirhead->startmasseq += 1;
 304         dir->newtail->endmasseq += 1;
 305
 306         /* Update directory check byte */
 307         dir->newtail->dircheckbyte = adfs_dir_checkbyte(dir);
 308
 309         /* Make sure the directory still validates correctly */
 310         ret = adfs_f_validate(dir);
 311         if (ret)
 312                 adfs_msg(dir->sb, KERN_ERR, "error: update broke directory");
 313
 314         return ret;
 315 }
 316
 317 const struct adfs_dir_ops adfs_f_dir_ops = {
 318         .read           = adfs_f_read,
 319         .iterate        = adfs_f_iterate,
 320         .setpos         = adfs_f_setpos,
 321         .getnext        = adfs_f_getnext,
 322         .update         = adfs_f_update,
 323         .commit         = adfs_f_commit,
 324 };