lunaix-os/kernel/fs/path_walk.c

   1 #include <lunaix/fs.h>
   2 #include <lunaix/mm/valloc.h>
   3 #include <lunaix/process.h>
   4 #include <lunaix/spike.h>
   5
   6 #include <usr/lunaix/fcntl_defs.h>
   7
   8 #include <klibc/string.h>
   9
  10 #define VFS_SYMLINK_DEPTH 16
  11 #define VFS_SYMLINK_MAXLEN 512
  12
  13 extern struct lru_zone *dnode_lru, *inode_lru;
  14
  15 int
  16 __vfs_walk(struct v_dnode* start,
  17            const char* path,
  18            struct v_dnode** dentry,
  19            struct hstr* component,
  20            int walk_options,
  21            size_t depth,
  22            char* fname_buffer)
  23 {
  24     int errno = 0;
  25     int i = 0, j = 0;
  26
  27     if (depth >= VFS_SYMLINK_DEPTH) {
  28         return ELOOP;
  29     }
  30
  31     if (path[0] == VFS_PATH_DELIM || !start) {
  32         if ((walk_options & VFS_WALK_FSRELATIVE) && start) {
  33             start = start->super_block->root;
  34         }
  35         else if (unlikely(!__current)) {
  36             start = vfs_sysroot;
  37         }
  38         else {
  39             start = __current->root ?: vfs_sysroot;
  40         }
  41
  42         if (unlikely(!start || !start->mnt)) {
  43             fail("vfs: no root");
  44         }
  45
  46         if (path[0] == VFS_PATH_DELIM) {
  47             i++;
  48         }
  49     }
  50
  51     assert(start);
  52
  53     struct v_dnode* dnode;
  54     struct v_dnode* current_level = start;
  55     struct v_inode* current_inode = current_level->inode;
  56
  57     struct hstr name = HSTR(fname_buffer, 0);
  58
  59     char current = path[i++], lookahead;
  60     while (current)
  61     {
  62         lookahead = path[i++];
  63
  64         if (current != VFS_PATH_DELIM)
  65         {
  66             if (j >= VFS_NAME_MAXLEN - 1) {
  67                 return ENAMETOOLONG;
  68             }
  69             if (!VFS_VALID_CHAR(current)) {
  70                 return EINVAL;
  71             }
  72             fname_buffer[j++] = current;
  73             if (lookahead) {
  74                 goto cont;
  75             }
  76         }
  77
  78         // handling cases like /^.*(\/+).*$/
  79         if (lookahead == VFS_PATH_DELIM) {
  80             goto cont;
  81         }
  82
  83         fname_buffer[j] = 0;
  84         name.len = j;
  85         hstr_rehash(&name, HSTR_FULL_HASH);
  86
  87         if (!lookahead && (walk_options & VFS_WALK_PARENT)) {
  88             if (component) {
  89                 hstrcpy(component, &name);
  90             }
  91             break;
  92         }
  93
  94         lock_dnode(current_level);
  95
  96         if (!check_allow_execute(current_inode)) {
  97             errno = EACCESS;
  98             goto error;
  99         }
 100
 101         dnode = vfs_dcache_lookup(current_level, &name);
 102
 103         if (!dnode)
 104         {
 105             dnode = vfs_d_alloc(current_level, &name);
 106
 107             if (!dnode) {
 108                 errno = ENOMEM;
 109                 goto error;
 110             }
 111
 112             lock_inode(current_inode);
 113
 114             errno = current_inode->ops->dir_lookup(current_inode, dnode);
 115
 116             if (errno == ENOENT && (walk_options & VFS_WALK_MKPARENT)) {
 117                 if (!current_inode->ops->mkdir) {
 118                     errno = ENOTSUP;
 119                 } else {
 120                     errno = current_inode->ops->mkdir(current_inode, dnode);
 121                 }
 122             }
 123
 124             vfs_dcache_add(current_level, dnode);
 125             unlock_inode(current_inode);
 126
 127             if (errno) {
 128                 unlock_dnode(current_level);
 129                 goto cleanup;
 130             }
 131         }
 132
 133         unlock_dnode(current_level);
 134
 135         j = 0;
 136         current_level = dnode;
 137         current_inode = current_level->inode;
 138
 139         assert(current_inode);
 140
 141         if (check_symlink_node(current_inode) &&
 142             !(walk_options & VFS_WALK_NOFOLLOW))
 143         {
 144             const char* link;
 145             struct v_inode_ops* iops;
 146
 147             iops = current_inode->ops;
 148
 149             if (!iops->read_symlink) {
 150                 errno = ENOTSUP;
 151                 goto error;
 152             }
 153
 154             lock_inode(current_inode);
 155
 156             errno = iops->read_symlink(current_inode, &link);
 157             if ((errno < 0)) {
 158                 unlock_inode(current_inode);
 159                 goto error;
 160             }
 161
 162             unlock_inode(current_inode);
 163
 164             errno = __vfs_walk(current_level->parent,
 165                                link,
 166                                &dnode,
 167                                NULL,
 168                                0,
 169                                depth + 1,
 170                                fname_buffer + name.len + 1);
 171
 172             if (errno) {
 173                 goto error;
 174             }
 175
 176             current_level = dnode;
 177             current_inode = dnode->inode;
 178         }
 179
 180     cont:
 181         current = lookahead;
 182     };
 183
 184     *dentry = current_level;
 185     return 0;
 186
 187 cleanup:
 188     vfs_d_free(dnode);
 189
 190 error:
 191     *dentry = NULL;
 192     return errno;
 193 }
 194
 195 int
 196 vfs_walk(struct v_dnode* start,
 197          const char* path,
 198          struct v_dnode** dentry,
 199          struct hstr* component,
 200          int options)
 201 {
 202     if (!path) {
 203         *dentry = NULL;
 204         return 0;
 205     }
 206
 207     // allocate a file name stack for path walking and recursion to resolve
 208     // symlink
 209     char* name_buffer = valloc(2048);
 210
 211     int errno =
 212       __vfs_walk(start, path, dentry, component, options, 0, name_buffer);
 213
 214     vfree(name_buffer);
 215     return errno;
 216 }
 217
 218 int
 219 vfs_walk_proc(const char* path,
 220               struct v_dnode** dentry,
 221               struct hstr* component,
 222               int options)
 223 {
 224     return vfs_walk(__current->cwd, path, dentry, component, options);
 225 }
 226
 227 int
 228 vfs_walkat(int fd, const char* path, int at_opts, struct v_dnode** dnode_out)
 229 {
 230     int errno, options = 0;
 231     struct v_dnode *root_dnode;
 232     struct v_fd* _fd;
 233
 234     if ((at_opts & AT_FDCWD)) {
 235         root_dnode = __current->cwd;
 236     }
 237     else
 238     {
 239         errno = vfs_getfd(fd, &_fd);
 240         if (errno) {
 241             return errno;
 242         }
 243
 244         root_dnode = _fd->file->dnode;
 245     }
 246
 247     if ((at_opts & AT_SYMLINK_NOFOLLOW)) {
 248         options |= VFS_WALK_NOFOLLOW;
 249     }
 250
 251     errno = vfs_walk(root_dnode, path, dnode_out, NULL, options);
 252     if (errno) {
 253         return errno;
 254     }
 255
 256     return 0;
 257 }