Kay Sievers | 2b2af54 | 2009-04-30 15:23:42 +0200 | [diff] [blame] | 1 | /* |
| 2 | * devtmpfs - kernel-maintained tmpfs-based /dev |
| 3 | * |
| 4 | * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org> |
| 5 | * |
| 6 | * During bootup, before any driver core device is registered, |
| 7 | * devtmpfs, a tmpfs-based filesystem is created. Every driver-core |
| 8 | * device which requests a device node, will add a node in this |
| 9 | * filesystem. The node is named after the the name of the device, |
| 10 | * or the susbsytem can provide a custom name. All devices are |
| 11 | * owned by root and have a mode of 0600. |
| 12 | */ |
| 13 | |
| 14 | #include <linux/kernel.h> |
| 15 | #include <linux/syscalls.h> |
| 16 | #include <linux/mount.h> |
| 17 | #include <linux/device.h> |
| 18 | #include <linux/genhd.h> |
| 19 | #include <linux/namei.h> |
| 20 | #include <linux/fs.h> |
| 21 | #include <linux/shmem_fs.h> |
| 22 | #include <linux/cred.h> |
| 23 | #include <linux/init_task.h> |
| 24 | |
| 25 | static struct vfsmount *dev_mnt; |
| 26 | |
| 27 | #if defined CONFIG_DEVTMPFS_MOUNT |
| 28 | static int dev_mount = 1; |
| 29 | #else |
| 30 | static int dev_mount; |
| 31 | #endif |
| 32 | |
| 33 | static int __init mount_param(char *str) |
| 34 | { |
| 35 | dev_mount = simple_strtoul(str, NULL, 0); |
| 36 | return 1; |
| 37 | } |
| 38 | __setup("devtmpfs.mount=", mount_param); |
| 39 | |
| 40 | static int dev_get_sb(struct file_system_type *fs_type, int flags, |
| 41 | const char *dev_name, void *data, struct vfsmount *mnt) |
| 42 | { |
| 43 | return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt); |
| 44 | } |
| 45 | |
| 46 | static struct file_system_type dev_fs_type = { |
| 47 | .name = "devtmpfs", |
| 48 | .get_sb = dev_get_sb, |
| 49 | .kill_sb = kill_litter_super, |
| 50 | }; |
| 51 | |
| 52 | #ifdef CONFIG_BLOCK |
| 53 | static inline int is_blockdev(struct device *dev) |
| 54 | { |
| 55 | return dev->class == &block_class; |
| 56 | } |
| 57 | #else |
| 58 | static inline int is_blockdev(struct device *dev) { return 0; } |
| 59 | #endif |
| 60 | |
| 61 | static int dev_mkdir(const char *name, mode_t mode) |
| 62 | { |
| 63 | struct nameidata nd; |
| 64 | struct dentry *dentry; |
| 65 | int err; |
| 66 | |
| 67 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 68 | name, LOOKUP_PARENT, &nd); |
| 69 | if (err) |
| 70 | return err; |
| 71 | |
| 72 | dentry = lookup_create(&nd, 1); |
| 73 | if (!IS_ERR(dentry)) { |
| 74 | err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); |
| 75 | dput(dentry); |
| 76 | } else { |
| 77 | err = PTR_ERR(dentry); |
| 78 | } |
| 79 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 80 | |
| 81 | path_put(&nd.path); |
| 82 | return err; |
| 83 | } |
| 84 | |
| 85 | static int create_path(const char *nodepath) |
| 86 | { |
| 87 | char *path; |
| 88 | struct nameidata nd; |
| 89 | int err = 0; |
| 90 | |
| 91 | path = kstrdup(nodepath, GFP_KERNEL); |
| 92 | if (!path) |
| 93 | return -ENOMEM; |
| 94 | |
| 95 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 96 | path, LOOKUP_PARENT, &nd); |
| 97 | if (err == 0) { |
| 98 | struct dentry *dentry; |
| 99 | |
| 100 | /* create directory right away */ |
| 101 | dentry = lookup_create(&nd, 1); |
| 102 | if (!IS_ERR(dentry)) { |
| 103 | err = vfs_mkdir(nd.path.dentry->d_inode, |
| 104 | dentry, 0755); |
| 105 | dput(dentry); |
| 106 | } |
| 107 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 108 | |
| 109 | path_put(&nd.path); |
| 110 | } else if (err == -ENOENT) { |
| 111 | char *s; |
| 112 | |
| 113 | /* parent directories do not exist, create them */ |
| 114 | s = path; |
| 115 | while (1) { |
| 116 | s = strchr(s, '/'); |
| 117 | if (!s) |
| 118 | break; |
| 119 | s[0] = '\0'; |
| 120 | err = dev_mkdir(path, 0755); |
| 121 | if (err && err != -EEXIST) |
| 122 | break; |
| 123 | s[0] = '/'; |
| 124 | s++; |
| 125 | } |
| 126 | } |
| 127 | |
| 128 | kfree(path); |
| 129 | return err; |
| 130 | } |
| 131 | |
| 132 | int devtmpfs_create_node(struct device *dev) |
| 133 | { |
| 134 | const char *tmp = NULL; |
| 135 | const char *nodename; |
| 136 | const struct cred *curr_cred; |
| 137 | mode_t mode; |
| 138 | struct nameidata nd; |
| 139 | struct dentry *dentry; |
| 140 | int err; |
| 141 | |
| 142 | if (!dev_mnt) |
| 143 | return 0; |
| 144 | |
| 145 | nodename = device_get_nodename(dev, &tmp); |
| 146 | if (!nodename) |
| 147 | return -ENOMEM; |
| 148 | |
| 149 | if (is_blockdev(dev)) |
| 150 | mode = S_IFBLK|0600; |
| 151 | else |
| 152 | mode = S_IFCHR|0600; |
| 153 | |
| 154 | curr_cred = override_creds(&init_cred); |
| 155 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 156 | nodename, LOOKUP_PARENT, &nd); |
| 157 | if (err == -ENOENT) { |
| 158 | /* create missing parent directories */ |
| 159 | create_path(nodename); |
| 160 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 161 | nodename, LOOKUP_PARENT, &nd); |
| 162 | if (err) |
| 163 | goto out; |
| 164 | } |
| 165 | |
| 166 | dentry = lookup_create(&nd, 0); |
| 167 | if (!IS_ERR(dentry)) { |
| 168 | err = vfs_mknod(nd.path.dentry->d_inode, |
| 169 | dentry, mode, dev->devt); |
| 170 | /* mark as kernel created inode */ |
| 171 | if (!err) |
| 172 | dentry->d_inode->i_private = &dev_mnt; |
| 173 | dput(dentry); |
| 174 | } else { |
| 175 | err = PTR_ERR(dentry); |
| 176 | } |
| 177 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 178 | |
| 179 | path_put(&nd.path); |
| 180 | out: |
| 181 | kfree(tmp); |
| 182 | revert_creds(curr_cred); |
| 183 | return err; |
| 184 | } |
| 185 | |
| 186 | static int dev_rmdir(const char *name) |
| 187 | { |
| 188 | struct nameidata nd; |
| 189 | struct dentry *dentry; |
| 190 | int err; |
| 191 | |
| 192 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 193 | name, LOOKUP_PARENT, &nd); |
| 194 | if (err) |
| 195 | return err; |
| 196 | |
| 197 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 198 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); |
| 199 | if (!IS_ERR(dentry)) { |
| 200 | if (dentry->d_inode) |
| 201 | err = vfs_rmdir(nd.path.dentry->d_inode, dentry); |
| 202 | else |
| 203 | err = -ENOENT; |
| 204 | dput(dentry); |
| 205 | } else { |
| 206 | err = PTR_ERR(dentry); |
| 207 | } |
| 208 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 209 | |
| 210 | path_put(&nd.path); |
| 211 | return err; |
| 212 | } |
| 213 | |
| 214 | static int delete_path(const char *nodepath) |
| 215 | { |
| 216 | const char *path; |
| 217 | int err = 0; |
| 218 | |
| 219 | path = kstrdup(nodepath, GFP_KERNEL); |
| 220 | if (!path) |
| 221 | return -ENOMEM; |
| 222 | |
| 223 | while (1) { |
| 224 | char *base; |
| 225 | |
| 226 | base = strrchr(path, '/'); |
| 227 | if (!base) |
| 228 | break; |
| 229 | base[0] = '\0'; |
| 230 | err = dev_rmdir(path); |
| 231 | if (err) |
| 232 | break; |
| 233 | } |
| 234 | |
| 235 | kfree(path); |
| 236 | return err; |
| 237 | } |
| 238 | |
| 239 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) |
| 240 | { |
| 241 | /* did we create it */ |
| 242 | if (inode->i_private != &dev_mnt) |
| 243 | return 0; |
| 244 | |
| 245 | /* does the dev_t match */ |
| 246 | if (is_blockdev(dev)) { |
| 247 | if (!S_ISBLK(stat->mode)) |
| 248 | return 0; |
| 249 | } else { |
| 250 | if (!S_ISCHR(stat->mode)) |
| 251 | return 0; |
| 252 | } |
| 253 | if (stat->rdev != dev->devt) |
| 254 | return 0; |
| 255 | |
| 256 | /* ours */ |
| 257 | return 1; |
| 258 | } |
| 259 | |
| 260 | int devtmpfs_delete_node(struct device *dev) |
| 261 | { |
| 262 | const char *tmp = NULL; |
| 263 | const char *nodename; |
| 264 | const struct cred *curr_cred; |
| 265 | struct nameidata nd; |
| 266 | struct dentry *dentry; |
| 267 | struct kstat stat; |
| 268 | int deleted = 1; |
| 269 | int err; |
| 270 | |
| 271 | if (!dev_mnt) |
| 272 | return 0; |
| 273 | |
| 274 | nodename = device_get_nodename(dev, &tmp); |
| 275 | if (!nodename) |
| 276 | return -ENOMEM; |
| 277 | |
| 278 | curr_cred = override_creds(&init_cred); |
| 279 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
| 280 | nodename, LOOKUP_PARENT, &nd); |
| 281 | if (err) |
| 282 | goto out; |
| 283 | |
| 284 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 285 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); |
| 286 | if (!IS_ERR(dentry)) { |
| 287 | if (dentry->d_inode) { |
| 288 | err = vfs_getattr(nd.path.mnt, dentry, &stat); |
| 289 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { |
| 290 | err = vfs_unlink(nd.path.dentry->d_inode, |
| 291 | dentry); |
| 292 | if (!err || err == -ENOENT) |
| 293 | deleted = 1; |
| 294 | } |
| 295 | } else { |
| 296 | err = -ENOENT; |
| 297 | } |
| 298 | dput(dentry); |
| 299 | } else { |
| 300 | err = PTR_ERR(dentry); |
| 301 | } |
| 302 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 303 | |
| 304 | path_put(&nd.path); |
| 305 | if (deleted && strchr(nodename, '/')) |
| 306 | delete_path(nodename); |
| 307 | out: |
| 308 | kfree(tmp); |
| 309 | revert_creds(curr_cred); |
| 310 | return err; |
| 311 | } |
| 312 | |
| 313 | /* |
| 314 | * If configured, or requested by the commandline, devtmpfs will be |
| 315 | * auto-mounted after the kernel mounted the root filesystem. |
| 316 | */ |
| 317 | int devtmpfs_mount(const char *mountpoint) |
| 318 | { |
| 319 | struct path path; |
| 320 | int err; |
| 321 | |
| 322 | if (!dev_mount) |
| 323 | return 0; |
| 324 | |
| 325 | if (!dev_mnt) |
| 326 | return 0; |
| 327 | |
| 328 | err = kern_path(mountpoint, LOOKUP_FOLLOW, &path); |
| 329 | if (err) |
| 330 | return err; |
| 331 | err = do_add_mount(dev_mnt, &path, 0, NULL); |
| 332 | if (err) |
| 333 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); |
| 334 | else |
| 335 | printk(KERN_INFO "devtmpfs: mounted\n"); |
| 336 | path_put(&path); |
| 337 | return err; |
| 338 | } |
| 339 | |
| 340 | /* |
| 341 | * Create devtmpfs instance, driver-core devices will add their device |
| 342 | * nodes here. |
| 343 | */ |
| 344 | int __init devtmpfs_init(void) |
| 345 | { |
| 346 | int err; |
| 347 | struct vfsmount *mnt; |
| 348 | |
| 349 | err = register_filesystem(&dev_fs_type); |
| 350 | if (err) { |
| 351 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " |
| 352 | "type %i\n", err); |
| 353 | return err; |
| 354 | } |
| 355 | |
| 356 | mnt = kern_mount(&dev_fs_type); |
| 357 | if (IS_ERR(mnt)) { |
| 358 | err = PTR_ERR(mnt); |
| 359 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); |
| 360 | unregister_filesystem(&dev_fs_type); |
| 361 | return err; |
| 362 | } |
| 363 | dev_mnt = mnt; |
| 364 | |
| 365 | printk(KERN_INFO "devtmpfs: initialized\n"); |
| 366 | return 0; |
| 367 | } |