lib/ext2fs/namei.c

   1 /*
   2  * namei.c --- ext2fs directory lookup operations
   3  *
   4  * Copyright (C) 1993, 1994, 1994, 1995 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Public
   8  * License.
   9  * %End-Header%
  10  */
  11
  12 #include <stdio.h>
  13 #include <string.h>
  14 #if HAVE_UNISTD_H
  15 #include <unistd.h>
  16 #endif
  17
  18 /* #define NAMEI_DEBUG */
  19
  20 #include "ext2_fs.h"
  21 #include "ext2fs.h"
  22
  23 static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
  24                             const char *pathname, size_t pathlen, int follow,
  25                             int link_count, char *buf, ext2_ino_t *res_inode);
  26
  27 static errcode_t follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
  28                              ext2_ino_t inode, int link_count,
  29                              char *buf, ext2_ino_t *res_inode)
  30 {
  31         char *pathname;
  32         char *buffer = 0;
  33         errcode_t retval;
  34         struct ext2_inode ei;
  35
  36 #ifdef NAMEI_DEBUG
  37         printf("follow_link: root=%lu, dir=%lu, inode=%lu, lc=%d\n",
  38                root, dir, inode, link_count);
  39
  40 #endif
  41         retval = ext2fs_read_inode (fs, inode, &ei);
  42         if (retval) return retval;
  43         if (!LINUX_S_ISLNK (ei.i_mode)) {
  44                 *res_inode = inode;
  45                 return 0;
  46         }
  47         if (link_count++ > 5) {
  48                 return EXT2_ET_SYMLINK_LOOP;
  49         }
  50         if (ext2fs_inode_data_blocks(fs,&ei)) {
  51                 retval = ext2fs_get_mem(fs->blocksize, &buffer);
  52                 if (retval)
  53                         return retval;
  54                 retval = io_channel_read_blk(fs->io, ei.i_block[0], 1, buffer);
  55                 if (retval) {
  56                         ext2fs_free_mem(&buffer);
  57                         return retval;
  58                 }
  59                 pathname = buffer;
  60         } else
  61                 pathname = (char *)&(ei.i_block[0]);
  62         retval = open_namei(fs, root, dir, pathname, ei.i_size, 1,
  63                             link_count, buf, res_inode);
  64         if (buffer)
  65                 ext2fs_free_mem(&buffer);
  66         return retval;
  67 }
  68
  69 /*
  70  * This routine interprets a pathname in the context of the current
  71  * directory and the root directory, and returns the inode of the
  72  * containing directory, and a pointer to the filename of the file
  73  * (pointing into the pathname) and the length of the filename.
  74  */
  75 static errcode_t dir_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
  76                            const char *pathname, int pathlen,
  77                            int link_count, char *buf,
  78                            const char **name, int *namelen,
  79                            ext2_ino_t *res_inode)
  80 {
  81         char c;
  82         const char *thisname;
  83         int len;
  84         ext2_ino_t inode;
  85         errcode_t retval;
  86
  87         if ((c = *pathname) == '/') {
  88                 dir = root;
  89                 pathname++;
  90                 pathlen--;
  91         }
  92         while (1) {
  93                 thisname = pathname;
  94                 for (len=0; --pathlen >= 0;len++) {
  95                         c = *(pathname++);
  96                         if (c == '/')
  97                                 break;
  98                 }
  99                 if (pathlen < 0)
 100                         break;
 101                 retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
 102                 if (retval) return retval;
 103                 retval = follow_link (fs, root, dir, inode,
 104                                       link_count, buf, &dir);
 105                 if (retval) return retval;
 106         }
 107         *name = thisname;
 108         *namelen = len;
 109         *res_inode = dir;
 110         return 0;
 111 }
 112
 113 static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
 114                             const char *pathname, size_t pathlen, int follow,
 115                             int link_count, char *buf, ext2_ino_t *res_inode)
 116 {
 117         const char *base_name;
 118         int namelen;
 119         ext2_ino_t dir, inode;
 120         errcode_t retval;
 121
 122 #ifdef NAMEI_DEBUG
 123         printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
 124                root, base, pathlen, pathname, link_count);
 125 #endif
 126         retval = dir_namei(fs, root, base, pathname, pathlen,
 127                            link_count, buf, &base_name, &namelen, &dir);
 128         if (retval) return retval;
 129         if (!namelen) {                     /* special case: '/usr/' etc */
 130                 *res_inode=dir;
 131                 return 0;
 132         }
 133         retval = ext2fs_lookup (fs, dir, base_name, namelen, buf, &inode);
 134         if (retval)
 135                 return retval;
 136         if (follow) {
 137                 retval = follow_link(fs, root, dir, inode, link_count,
 138                                      buf, &inode);
 139                 if (retval)
 140                         return retval;
 141         }
 142 #ifdef NAMEI_DEBUG
 143         printf("open_namei: (link_count=%d) returns %lu\n",
 144                link_count, inode);
 145 #endif
 146         *res_inode = inode;
 147         return 0;
 148 }
 149
 150 errcode_t ext2fs_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 151                        const char *name, ext2_ino_t *inode)
 152 {
 153         char *buf;
 154         errcode_t retval;
 155
 156         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 157
 158         retval = ext2fs_get_mem(fs->blocksize, &buf);
 159         if (retval)
 160                 return retval;
 161
 162         retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
 163                             buf, inode);
 164
 165         ext2fs_free_mem(&buf);
 166         return retval;
 167 }
 168
 169 errcode_t ext2fs_namei_follow(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 170                               const char *name, ext2_ino_t *inode)
 171 {
 172         char *buf;
 173         errcode_t retval;
 174
 175         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 176
 177         retval = ext2fs_get_mem(fs->blocksize, &buf);
 178         if (retval)
 179                 return retval;
 180
 181         retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
 182                             buf, inode);
 183
 184         ext2fs_free_mem(&buf);
 185         return retval;
 186 }
 187
 188 errcode_t ext2fs_follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 189                         ext2_ino_t inode, ext2_ino_t *res_inode)
 190 {
 191         char *buf;
 192         errcode_t retval;
 193
 194         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 195
 196         retval = ext2fs_get_mem(fs->blocksize, &buf);
 197         if (retval)
 198                 return retval;
 199
 200         retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);
 201
 202         ext2fs_free_mem(&buf);
 203         return retval;
 204 }
 205