fs/adfs/dir_f.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/fs/adfs/dir_f.c
0004  *
0005  * Copyright (C) 1997-1999 Russell King
0006  *
0007  *  E and F format directory handling
0008  */
0009 #include "adfs.h"
0010 #include "dir_f.h"
0011
0012 /*
0013  * Read an (unaligned) value of length 1..4 bytes
0014  */
0015 static inline unsigned int adfs_readval(unsigned char *p, int len)
0016 {
0017     unsigned int val = 0;
0018
0019     switch (len) {
0020     case 4:     val |= p[3] << 24;
0021         fallthrough;
0022     case 3:     val |= p[2] << 16;
0023         fallthrough;
0024     case 2:     val |= p[1] << 8;
0025         fallthrough;
0026     default:    val |= p[0];
0027     }
0028     return val;
0029 }
0030
0031 static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
0032 {
0033     switch (len) {
0034     case 4:     p[3] = val >> 24;
0035         fallthrough;
0036     case 3:     p[2] = val >> 16;
0037         fallthrough;
0038     case 2:     p[1] = val >> 8;
0039         fallthrough;
0040     default:    p[0] = val;
0041     }
0042 }
0043
0044 #define ror13(v) ((v >> 13) | (v << 19))
0045
0046 #define dir_u8(idx)             \
0047     ({ int _buf = idx >> blocksize_bits;    \
0048        int _off = idx - (_buf << blocksize_bits);\
0049       *(u8 *)(bh[_buf]->b_data + _off); \
0050     })
0051
0052 #define dir_u32(idx)                \
0053     ({ int _buf = idx >> blocksize_bits;    \
0054        int _off = idx - (_buf << blocksize_bits);\
0055       *(__le32 *)(bh[_buf]->b_data + _off); \
0056     })
0057
0058 #define bufoff(_bh,_idx)            \
0059     ({ int _buf = _idx >> blocksize_bits;   \
0060        int _off = _idx - (_buf << blocksize_bits);\
0061       (void *)(_bh[_buf]->b_data + _off);   \
0062     })
0063
0064 /*
0065  * There are some algorithms that are nice in
0066  * assembler, but a bitch in C...  This is one
0067  * of them.
0068  */
0069 static u8
0070 adfs_dir_checkbyte(const struct adfs_dir *dir)
0071 {
0072     struct buffer_head * const *bh = dir->bh;
0073     const int blocksize_bits = dir->sb->s_blocksize_bits;
0074     union { __le32 *ptr32; u8 *ptr8; } ptr, end;
0075     u32 dircheck = 0;
0076     int last = 5 - 26;
0077     int i = 0;
0078
0079     /*
0080      * Accumulate each word up to the last whole
0081      * word of the last directory entry.  This
0082      * can spread across several buffer heads.
0083      */
0084     do {
0085         last += 26;
0086         do {
0087             dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);
0088
0089             i += sizeof(u32);
0090         } while (i < (last & ~3));
0091     } while (dir_u8(last) != 0);
0092
0093     /*
0094      * Accumulate the last few bytes.  These
0095      * bytes will be within the same bh.
0096      */
0097     if (i != last) {
0098         ptr.ptr8 = bufoff(bh, i);
0099         end.ptr8 = ptr.ptr8 + last - i;
0100
0101         do {
0102             dircheck = *ptr.ptr8++ ^ ror13(dircheck);
0103         } while (ptr.ptr8 < end.ptr8);
0104     }
0105
0106     /*
0107      * The directory tail is in the final bh
0108      * Note that contary to the RISC OS PRMs,
0109      * the first few bytes are NOT included
0110      * in the check.  All bytes are in the
0111      * same bh.
0112      */
0113     ptr.ptr8 = bufoff(bh, 2008);
0114     end.ptr8 = ptr.ptr8 + 36;
0115
0116     do {
0117         __le32 v = *ptr.ptr32++;
0118         dircheck = le32_to_cpu(v) ^ ror13(dircheck);
0119     } while (ptr.ptr32 < end.ptr32);
0120
0121     return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
0122 }
0123
0124 static int adfs_f_validate(struct adfs_dir *dir)
0125 {
0126     struct adfs_dirheader *head = dir->dirhead;
0127     struct adfs_newdirtail *tail = dir->newtail;
0128
0129     if (head->startmasseq != tail->endmasseq ||
0130         tail->dirlastmask || tail->reserved[0] || tail->reserved[1] ||
0131         (memcmp(&head->startname, "Nick", 4) &&
0132          memcmp(&head->startname, "Hugo", 4)) ||
0133         memcmp(&head->startname, &tail->endname, 4) ||
0134         adfs_dir_checkbyte(dir) != tail->dircheckbyte)
0135         return -EIO;
0136
0137     return 0;
0138 }
0139
0140 /* Read and check that a directory is valid */
0141 static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
0142                struct adfs_dir *dir)
0143 {
0144     const unsigned int blocksize_bits = sb->s_blocksize_bits;
0145     int ret;
0146
0147     if (size && size != ADFS_NEWDIR_SIZE)
0148         return -EIO;
0149
0150     ret = adfs_dir_read_buffers(sb, indaddr, ADFS_NEWDIR_SIZE, dir);
0151     if (ret)
0152         return ret;
0153
0154     dir->dirhead = bufoff(dir->bh, 0);
0155     dir->newtail = bufoff(dir->bh, 2007);
0156
0157     if (adfs_f_validate(dir))
0158         goto bad_dir;
0159
0160     dir->parent_id = adfs_readval(dir->newtail->dirparent, 3);
0161
0162     return 0;
0163
0164 bad_dir:
0165     adfs_error(sb, "dir %06x is corrupted", indaddr);
0166     adfs_dir_relse(dir);
0167
0168     return -EIO;
0169 }
0170
0171 /*
0172  * convert a disk-based directory entry to a Linux ADFS directory entry
0173  */
0174 static inline void
0175 adfs_dir2obj(struct adfs_dir *dir, struct object_info *obj,
0176     struct adfs_direntry *de)
0177 {
0178     unsigned int name_len;
0179
0180     for (name_len = 0; name_len < ADFS_F_NAME_LEN; name_len++) {
0181         if (de->dirobname[name_len] < ' ')
0182             break;
0183
0184         obj->name[name_len] = de->dirobname[name_len];
0185     }
0186
0187     obj->name_len = name_len;
0188     obj->indaddr  = adfs_readval(de->dirinddiscadd, 3);
0189     obj->loadaddr = adfs_readval(de->dirload, 4);
0190     obj->execaddr = adfs_readval(de->direxec, 4);
0191     obj->size     = adfs_readval(de->dirlen,  4);
0192     obj->attr     = de->newdiratts;
0193
0194     adfs_object_fixup(dir, obj);
0195 }
0196
0197 /*
0198  * convert a Linux ADFS directory entry to a disk-based directory entry
0199  */
0200 static inline void
0201 adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
0202 {
0203     adfs_writeval(de->dirinddiscadd, 3, obj->indaddr);
0204     adfs_writeval(de->dirload, 4, obj->loadaddr);
0205     adfs_writeval(de->direxec, 4, obj->execaddr);
0206     adfs_writeval(de->dirlen,  4, obj->size);
0207     de->newdiratts = obj->attr;
0208 }
0209
0210 /*
0211  * get a directory entry.  Note that the caller is responsible
0212  * for holding the relevant locks.
0213  */
0214 static int
0215 __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
0216 {
0217     struct adfs_direntry de;
0218     int ret;
0219
0220     ret = adfs_dir_copyfrom(&de, dir, pos, 26);
0221     if (ret)
0222         return ret;
0223
0224     if (!de.dirobname[0])
0225         return -ENOENT;
0226
0227     adfs_dir2obj(dir, obj, &de);
0228
0229     return 0;
0230 }
0231
0232 static int
0233 adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
0234 {
0235     if (fpos >= ADFS_NUM_DIR_ENTRIES)
0236         return -ENOENT;
0237
0238     dir->pos = 5 + fpos * 26;
0239     return 0;
0240 }
0241
0242 static int
0243 adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
0244 {
0245     unsigned int ret;
0246
0247     ret = __adfs_dir_get(dir, dir->pos, obj);
0248     if (ret == 0)
0249         dir->pos += 26;
0250
0251     return ret;
0252 }
0253
0254 static int adfs_f_iterate(struct adfs_dir *dir, struct dir_context *ctx)
0255 {
0256     struct object_info obj;
0257     int pos = 5 + (ctx->pos - 2) * 26;
0258
0259     while (ctx->pos < 2 + ADFS_NUM_DIR_ENTRIES) {
0260         if (__adfs_dir_get(dir, pos, &obj))
0261             break;
0262         if (!dir_emit(ctx, obj.name, obj.name_len,
0263                   obj.indaddr, DT_UNKNOWN))
0264             break;
0265         pos += 26;
0266         ctx->pos++;
0267     }
0268     return 0;
0269 }
0270
0271 static int adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
0272 {
0273     struct adfs_direntry de;
0274     int offset, ret;
0275
0276     offset = 5 - (int)sizeof(de);
0277
0278     do {
0279         offset += sizeof(de);
0280         ret = adfs_dir_copyfrom(&de, dir, offset, sizeof(de));
0281         if (ret) {
0282             adfs_error(dir->sb, "error reading directory entry");
0283             return -ENOENT;
0284         }
0285         if (!de.dirobname[0]) {
0286             adfs_error(dir->sb, "unable to locate entry to update");
0287             return -ENOENT;
0288         }
0289     } while (adfs_readval(de.dirinddiscadd, 3) != obj->indaddr);
0290
0291     /* Update the directory entry with the new object state */
0292     adfs_obj2dir(&de, obj);
0293
0294     /* Write the directory entry back to the directory */
0295     return adfs_dir_copyto(dir, offset, &de, 26);
0296 }
0297
0298 static int adfs_f_commit(struct adfs_dir *dir)
0299 {
0300     int ret;
0301
0302     /* Increment directory sequence number */
0303     dir->dirhead->startmasseq += 1;
0304     dir->newtail->endmasseq += 1;
0305
0306     /* Update directory check byte */
0307     dir->newtail->dircheckbyte = adfs_dir_checkbyte(dir);
0308
0309     /* Make sure the directory still validates correctly */
0310     ret = adfs_f_validate(dir);
0311     if (ret)
0312         adfs_msg(dir->sb, KERN_ERR, "error: update broke directory");
0313
0314     return ret;
0315 }
0316
0317 const struct adfs_dir_ops adfs_f_dir_ops = {
0318     .read       = adfs_f_read,
0319     .iterate    = adfs_f_iterate,
0320     .setpos     = adfs_f_setpos,
0321     .getnext    = adfs_f_getnext,
0322     .update     = adfs_f_update,
0323     .commit     = adfs_f_commit,
0324 };