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             unlock_dnode(current_level);
  99             goto error;
 100         }
 101
 102         dnode = vfs_dcache_lookup(current_level, &name);
 103
 104         if (!dnode)
 105         {
 106             dnode = vfs_d_alloc(current_level, &name);
 107
 108             if (!dnode) {
 109                 errno = ENOMEM;
 110                 unlock_dnode(current_level);
 111                 goto error;
 112             }
 113
 114             lock_inode(current_inode);
 115
 116             errno = current_inode->ops->dir_lookup(current_inode, dnode);
 117
 118             if (errno == ENOENT && (walk_options & VFS_WALK_MKPARENT)) {
 119                 if (!current_inode->ops->mkdir) {
 120                     errno = ENOTSUP;
 121                 } else {
 122                     errno = current_inode->ops->mkdir(current_inode, dnode);
 123                 }
 124             }
 125
 126             vfs_dcache_add(current_level, dnode);
 127             unlock_inode(current_inode);
 128
 129             if (errno) {
 130                 unlock_dnode(current_level);
 131                 goto cleanup;
 132             }
 133         }
 134
 135         unlock_dnode(current_level);
 136
 137         j = 0;
 138         current_level = dnode;
 139         current_inode = current_level->inode;
 140
 141         assert(current_inode);
 142
 143         if (check_symlink_node(current_inode) &&
 144             !(walk_options & VFS_WALK_NOFOLLOW))
 145         {
 146             const char* link;
 147             struct v_inode_ops* iops;
 148
 149             iops = current_inode->ops;
 150
 151             if (!iops->read_symlink) {
 152                 errno = ENOTSUP;
 153                 goto error;
 154             }
 155
 156             lock_inode(current_inode);
 157
 158             errno = iops->read_symlink(current_inode, &link);
 159             if ((errno < 0)) {
 160                 unlock_inode(current_inode);
 161                 goto error;
 162             }
 163
 164             unlock_inode(current_inode);
 165
 166             errno = __vfs_walk(current_level->parent,
 167                                link,
 168                                &dnode,
 169                                NULL,
 170                                0,
 171                                depth + 1,
 172                                fname_buffer + name.len + 1);
 173
 174             if (errno) {
 175                 goto error;
 176             }
 177
 178             current_level = dnode;
 179             current_inode = dnode->inode;
 180         }
 181
 182     cont:
 183         current = lookahead;
 184     };
 185
 186     *dentry = current_level;
 187     return 0;
 188
 189 cleanup:
 190     vfs_d_free(dnode);
 191
 192 error:
 193     *dentry = NULL;
 194     return errno;
 195 }
 196
 197 int
 198 vfs_walk(struct v_dnode* start,
 199          const char* path,
 200          struct v_dnode** dentry,
 201          struct hstr* component,
 202          int options)
 203 {
 204     if (!path) {
 205         *dentry = NULL;
 206         return 0;
 207     }
 208
 209     // allocate a file name stack for path walking and recursion to resolve
 210     // symlink
 211     char* name_buffer = valloc(2048);
 212
 213     int errno =
 214       __vfs_walk(start, path, dentry, component, options, 0, name_buffer);
 215
 216     vfree(name_buffer);
 217     return errno;
 218 }
 219
 220 int
 221 vfs_walk_proc(const char* path,
 222               struct v_dnode** dentry,
 223               struct hstr* component,
 224               int options)
 225 {
 226     return vfs_walk(__current->cwd, path, dentry, component, options);
 227 }
 228
 229 int
 230 vfs_walkat(int fd, const char* path, int at_opts, struct v_dnode** dnode_out)
 231 {
 232     int errno, options = 0;
 233     struct v_dnode *root_dnode;
 234     struct v_fd* _fd;
 235
 236     if ((at_opts & AT_FDCWD)) {
 237         root_dnode = __current->cwd;
 238     }
 239     else
 240     {
 241         errno = vfs_getfd(fd, &_fd);
 242         if (errno) {
 243             return errno;
 244         }
 245
 246         root_dnode = _fd->file->dnode;
 247     }
 248
 249     if ((at_opts & AT_SYMLINK_NOFOLLOW)) {
 250         options |= VFS_WALK_NOFOLLOW;
 251     }
 252
 253     errno = vfs_walk(root_dnode, path, dnode_out, NULL, options);
 254     if (errno) {
 255         return errno;
 256     }
 257
 258     return 0;
 259 }