e2fsprogs/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         ext2fs_free_mem(&buffer);
  65         return retval;
  66 }
  67
  68 /*
  69  * This routine interprets a pathname in the context of the current
  70  * directory and the root directory, and returns the inode of the
  71  * containing directory, and a pointer to the filename of the file
  72  * (pointing into the pathname) and the length of the filename.
  73  */
  74 static errcode_t dir_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t dir,
  75                            const char *pathname, int pathlen,
  76                            int link_count, char *buf,
  77                            const char **name, int *namelen,
  78                            ext2_ino_t *res_inode)
  79 {
  80         char c;
  81         const char *thisname;
  82         int len;
  83         ext2_ino_t inode;
  84         errcode_t retval;
  85
  86         if ((c = *pathname) == '/') {
  87                 dir = root;
  88                 pathname++;
  89                 pathlen--;
  90         }
  91         while (1) {
  92                 thisname = pathname;
  93                 for (len=0; --pathlen >= 0;len++) {
  94                         c = *(pathname++);
  95                         if (c == '/')
  96                                 break;
  97                 }
  98                 if (pathlen < 0)
  99                         break;
 100                 retval = ext2fs_lookup (fs, dir, thisname, len, buf, &inode);
 101                 if (retval) return retval;
 102                 retval = follow_link (fs, root, dir, inode,
 103                                       link_count, buf, &dir);
 104                 if (retval) return retval;
 105         }
 106         *name = thisname;
 107         *namelen = len;
 108         *res_inode = dir;
 109         return 0;
 110 }
 111
 112 static errcode_t open_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t base,
 113                             const char *pathname, size_t pathlen, int follow,
 114                             int link_count, char *buf, ext2_ino_t *res_inode)
 115 {
 116         const char *basename;
 117         int namelen;
 118         ext2_ino_t dir, inode;
 119         errcode_t retval;
 120
 121 #ifdef NAMEI_DEBUG
 122         printf("open_namei: root=%lu, dir=%lu, path=%*s, lc=%d\n",
 123                root, base, pathlen, pathname, link_count);
 124 #endif
 125         retval = dir_namei(fs, root, base, pathname, pathlen,
 126                            link_count, buf, &basename, &namelen, &dir);
 127         if (retval) return retval;
 128         if (!namelen) {                     /* special case: '/usr/' etc */
 129                 *res_inode=dir;
 130                 return 0;
 131         }
 132         retval = ext2fs_lookup (fs, dir, basename, namelen, buf, &inode);
 133         if (retval)
 134                 return retval;
 135         if (follow) {
 136                 retval = follow_link(fs, root, dir, inode, link_count,
 137                                      buf, &inode);
 138                 if (retval)
 139                         return retval;
 140         }
 141 #ifdef NAMEI_DEBUG
 142         printf("open_namei: (link_count=%d) returns %lu\n",
 143                link_count, inode);
 144 #endif
 145         *res_inode = inode;
 146         return 0;
 147 }
 148
 149 errcode_t ext2fs_namei(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 150                        const char *name, ext2_ino_t *inode)
 151 {
 152         char *buf;
 153         errcode_t retval;
 154
 155         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 156
 157         retval = ext2fs_get_mem(fs->blocksize, &buf);
 158         if (retval)
 159                 return retval;
 160
 161         retval = open_namei(fs, root, cwd, name, strlen(name), 0, 0,
 162                             buf, inode);
 163
 164         ext2fs_free_mem(&buf);
 165         return retval;
 166 }
 167
 168 errcode_t ext2fs_namei_follow(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 169                               const char *name, ext2_ino_t *inode)
 170 {
 171         char *buf;
 172         errcode_t retval;
 173
 174         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 175
 176         retval = ext2fs_get_mem(fs->blocksize, &buf);
 177         if (retval)
 178                 return retval;
 179
 180         retval = open_namei(fs, root, cwd, name, strlen(name), 1, 0,
 181                             buf, inode);
 182
 183         ext2fs_free_mem(&buf);
 184         return retval;
 185 }
 186
 187 errcode_t ext2fs_follow_link(ext2_filsys fs, ext2_ino_t root, ext2_ino_t cwd,
 188                         ext2_ino_t inode, ext2_ino_t *res_inode)
 189 {
 190         char *buf;
 191         errcode_t retval;
 192
 193         EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 194
 195         retval = ext2fs_get_mem(fs->blocksize, &buf);
 196         if (retval)
 197                 return retval;
 198
 199         retval = follow_link(fs, root, cwd, inode, 0, buf, res_inode);
 200
 201         ext2fs_free_mem(&buf);
 202         return retval;
 203 }
 204