Pileus Git - ~andy/linux/blob - drivers/base/devtmpfs.c

   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.
  10  * By default, all devices are named after the name of the device,
  11  * owned by root and have a default mode of 0600. Subsystems can
  12  * overwrite the default setting if needed.
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/syscalls.h>
  17 #include <linux/mount.h>
  18 #include <linux/device.h>
  19 #include <linux/genhd.h>
  20 #include <linux/namei.h>
  21 #include <linux/fs.h>
  22 #include <linux/shmem_fs.h>
  23 #include <linux/ramfs.h>
  24 #include <linux/sched.h>
  25 #include <linux/slab.h>
  26 #include <linux/kthread.h>
  27
  28 static struct task_struct *thread;
  29
  30 #if defined CONFIG_DEVTMPFS_MOUNT
  31 static int mount_dev = 1;
  32 #else
  33 static int mount_dev;
  34 #endif
  35
  36 static DEFINE_SPINLOCK(req_lock);
  37
  38 static struct req {
  39         struct req *next;
  40         struct completion done;
  41         int err;
  42         const char *name;
  43         umode_t mode;   /* 0 => delete */
  44         uid_t uid;
  45         gid_t gid;
  46         struct device *dev;
  47 } *requests;
  48
  49 static int __init mount_param(char *str)
  50 {
  51         mount_dev = simple_strtoul(str, NULL, 0);
  52         return 1;
  53 }
  54 __setup("devtmpfs.mount=", mount_param);
  55
  56 static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
  57                       const char *dev_name, void *data)
  58 {
  59 #ifdef CONFIG_TMPFS
  60         return mount_single(fs_type, flags, data, shmem_fill_super);
  61 #else
  62         return mount_single(fs_type, flags, data, ramfs_fill_super);
  63 #endif
  64 }
  65
  66 static struct file_system_type dev_fs_type = {
  67         .name = "devtmpfs",
  68         .mount = dev_mount,
  69         .kill_sb = kill_litter_super,
  70 };
  71
  72 #ifdef CONFIG_BLOCK
  73 static inline int is_blockdev(struct device *dev)
  74 {
  75         return dev->class == &block_class;
  76 }
  77 #else
  78 static inline int is_blockdev(struct device *dev) { return 0; }
  79 #endif
  80
  81 int devtmpfs_create_node(struct device *dev)
  82 {
  83         const char *tmp = NULL;
  84         struct req req;
  85
  86         if (!thread)
  87                 return 0;
  88
  89         req.mode = 0;
  90         req.uid = 0;
  91         req.gid = 0;
  92         req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
  93         if (!req.name)
  94                 return -ENOMEM;
  95
  96         if (req.mode == 0)
  97                 req.mode = 0600;
  98         if (is_blockdev(dev))
  99                 req.mode |= S_IFBLK;
 100         else
 101                 req.mode |= S_IFCHR;
 102
 103         req.dev = dev;
 104
 105         init_completion(&req.done);
 106
 107         spin_lock(&req_lock);
 108         req.next = requests;
 109         requests = &req;
 110         spin_unlock(&req_lock);
 111
 112         wake_up_process(thread);
 113         wait_for_completion(&req.done);
 114
 115         kfree(tmp);
 116
 117         return req.err;
 118 }
 119
 120 int devtmpfs_delete_node(struct device *dev)
 121 {
 122         const char *tmp = NULL;
 123         struct req req;
 124
 125         if (!thread)
 126                 return 0;
 127
 128         req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
 129         if (!req.name)
 130                 return -ENOMEM;
 131
 132         req.mode = 0;
 133         req.dev = dev;
 134
 135         init_completion(&req.done);
 136
 137         spin_lock(&req_lock);
 138         req.next = requests;
 139         requests = &req;
 140         spin_unlock(&req_lock);
 141
 142         wake_up_process(thread);
 143         wait_for_completion(&req.done);
 144
 145         kfree(tmp);
 146         return req.err;
 147 }
 148
 149 static int dev_mkdir(const char *name, umode_t mode)
 150 {
 151         struct dentry *dentry;
 152         struct path path;
 153         int err;
 154
 155         dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
 156         if (IS_ERR(dentry))
 157                 return PTR_ERR(dentry);
 158
 159         err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
 160         if (!err)
 161                 /* mark as kernel-created inode */
 162                 dentry->d_inode->i_private = &thread;
 163         done_path_create(&path, dentry);
 164         return err;
 165 }
 166
 167 static int create_path(const char *nodepath)
 168 {
 169         char *path;
 170         char *s;
 171         int err = 0;
 172
 173         /* parent directories do not exist, create them */
 174         path = kstrdup(nodepath, GFP_KERNEL);
 175         if (!path)
 176                 return -ENOMEM;
 177
 178         s = path;
 179         for (;;) {
 180                 s = strchr(s, '/');
 181                 if (!s)
 182                         break;
 183                 s[0] = '\0';
 184                 err = dev_mkdir(path, 0755);
 185                 if (err && err != -EEXIST)
 186                         break;
 187                 s[0] = '/';
 188                 s++;
 189         }
 190         kfree(path);
 191         return err;
 192 }
 193
 194 static int handle_create(const char *nodename, umode_t mode, uid_t uid,
 195                          gid_t gid, struct device *dev)
 196 {
 197         struct dentry *dentry;
 198         struct path path;
 199         int err;
 200
 201         dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
 202         if (dentry == ERR_PTR(-ENOENT)) {
 203                 create_path(nodename);
 204                 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
 205         }
 206         if (IS_ERR(dentry))
 207                 return PTR_ERR(dentry);
 208
 209         err = vfs_mknod(path.dentry->d_inode, dentry, mode, dev->devt);
 210         if (!err) {
 211                 struct iattr newattrs;
 212
 213                 newattrs.ia_mode = mode;
 214                 newattrs.ia_uid = uid;
 215                 newattrs.ia_gid = gid;
 216                 newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
 217                 mutex_lock(&dentry->d_inode->i_mutex);
 218                 notify_change(dentry, &newattrs);
 219                 mutex_unlock(&dentry->d_inode->i_mutex);
 220
 221                 /* mark as kernel-created inode */
 222                 dentry->d_inode->i_private = &thread;
 223         }
 224         done_path_create(&path, dentry);
 225         return err;
 226 }
 227
 228 static int dev_rmdir(const char *name)
 229 {
 230         struct path parent;
 231         struct dentry *dentry;
 232         int err;
 233
 234         dentry = kern_path_locked(name, &parent);
 235         if (IS_ERR(dentry))
 236                 return PTR_ERR(dentry);
 237         if (dentry->d_inode) {
 238                 if (dentry->d_inode->i_private == &thread)
 239                         err = vfs_rmdir(parent.dentry->d_inode, dentry);
 240                 else
 241                         err = -EPERM;
 242         } else {
 243                 err = -ENOENT;
 244         }
 245         dput(dentry);
 246         mutex_unlock(&parent.dentry->d_inode->i_mutex);
 247         path_put(&parent);
 248         return err;
 249 }
 250
 251 static int delete_path(const char *nodepath)
 252 {
 253         const char *path;
 254         int err = 0;
 255
 256         path = kstrdup(nodepath, GFP_KERNEL);
 257         if (!path)
 258                 return -ENOMEM;
 259
 260         for (;;) {
 261                 char *base;
 262
 263                 base = strrchr(path, '/');
 264                 if (!base)
 265                         break;
 266                 base[0] = '\0';
 267                 err = dev_rmdir(path);
 268                 if (err)
 269                         break;
 270         }
 271
 272         kfree(path);
 273         return err;
 274 }
 275
 276 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
 277 {
 278         /* did we create it */
 279         if (inode->i_private != &thread)
 280                 return 0;
 281
 282         /* does the dev_t match */
 283         if (is_blockdev(dev)) {
 284                 if (!S_ISBLK(stat->mode))
 285                         return 0;
 286         } else {
 287                 if (!S_ISCHR(stat->mode))
 288                         return 0;
 289         }
 290         if (stat->rdev != dev->devt)
 291                 return 0;
 292
 293         /* ours */
 294         return 1;
 295 }
 296
 297 static int handle_remove(const char *nodename, struct device *dev)
 298 {
 299         struct path parent;
 300         struct dentry *dentry;
 301         int deleted = 1;
 302         int err;
 303
 304         dentry = kern_path_locked(nodename, &parent);
 305         if (IS_ERR(dentry))
 306                 return PTR_ERR(dentry);
 307
 308         if (dentry->d_inode) {
 309                 struct kstat stat;
 310                 struct path p = {.mnt = parent.mnt, .dentry = dentry};
 311                 err = vfs_getattr(&p, &stat);
 312                 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
 313                         struct iattr newattrs;
 314                         /*
 315                          * before unlinking this node, reset permissions
 316                          * of possible references like hardlinks
 317                          */
 318                         newattrs.ia_uid = GLOBAL_ROOT_UID;
 319                         newattrs.ia_gid = GLOBAL_ROOT_GID;
 320                         newattrs.ia_mode = stat.mode & ~0777;
 321                         newattrs.ia_valid =
 322                                 ATTR_UID|ATTR_GID|ATTR_MODE;
 323                         mutex_lock(&dentry->d_inode->i_mutex);
 324                         notify_change(dentry, &newattrs);
 325                         mutex_unlock(&dentry->d_inode->i_mutex);
 326                         err = vfs_unlink(parent.dentry->d_inode, dentry);
 327                         if (!err || err == -ENOENT)
 328                                 deleted = 1;
 329                 }
 330         } else {
 331                 err = -ENOENT;
 332         }
 333         dput(dentry);
 334         mutex_unlock(&parent.dentry->d_inode->i_mutex);
 335
 336         path_put(&parent);
 337         if (deleted && strchr(nodename, '/'))
 338                 delete_path(nodename);
 339         return err;
 340 }
 341
 342 /*
 343  * If configured, or requested by the commandline, devtmpfs will be
 344  * auto-mounted after the kernel mounted the root filesystem.
 345  */
 346 int devtmpfs_mount(const char *mntdir)
 347 {
 348         int err;
 349
 350         if (!mount_dev)
 351                 return 0;
 352
 353         if (!thread)
 354                 return 0;
 355
 356         err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
 357         if (err)
 358                 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
 359         else
 360                 printk(KERN_INFO "devtmpfs: mounted\n");
 361         return err;
 362 }
 363
 364 static DECLARE_COMPLETION(setup_done);
 365
 366 static int handle(const char *name, umode_t mode, uid_t uid, gid_t gid,
 367                   struct device *dev)
 368 {
 369         if (mode)
 370                 return handle_create(name, mode, uid, gid, dev);
 371         else
 372                 return handle_remove(name, dev);
 373 }
 374
 375 static int devtmpfsd(void *p)
 376 {
 377         char options[] = "mode=0755";
 378         int *err = p;
 379         *err = sys_unshare(CLONE_NEWNS);
 380         if (*err)
 381                 goto out;
 382         *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
 383         if (*err)
 384                 goto out;
 385         sys_chdir("/.."); /* will traverse into overmounted root */
 386         sys_chroot(".");
 387         complete(&setup_done);
 388         while (1) {
 389                 spin_lock(&req_lock);
 390                 while (requests) {
 391                         struct req *req = requests;
 392                         requests = NULL;
 393                         spin_unlock(&req_lock);
 394                         while (req) {
 395                                 struct req *next = req->next;
 396                                 req->err = handle(req->name, req->mode,
 397                                                   req->uid, req->gid, req->dev);
 398                                 complete(&req->done);
 399                                 req = next;
 400                         }
 401                         spin_lock(&req_lock);
 402                 }
 403                 __set_current_state(TASK_INTERRUPTIBLE);
 404                 spin_unlock(&req_lock);
 405                 schedule();
 406         }
 407         return 0;
 408 out:
 409         complete(&setup_done);
 410         return *err;
 411 }
 412
 413 /*
 414  * Create devtmpfs instance, driver-core devices will add their device
 415  * nodes here.
 416  */
 417 int __init devtmpfs_init(void)
 418 {
 419         int err = register_filesystem(&dev_fs_type);
 420         if (err) {
 421                 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
 422                        "type %i\n", err);
 423                 return err;
 424         }
 425
 426         thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
 427         if (!IS_ERR(thread)) {
 428                 wait_for_completion(&setup_done);
 429         } else {
 430                 err = PTR_ERR(thread);
 431                 thread = NULL;
 432         }
 433
 434         if (err) {
 435                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
 436                 unregister_filesystem(&dev_fs_type);
 437                 return err;
 438         }
 439
 440         printk(KERN_INFO "devtmpfs: initialized\n");
 441         return 0;
 442 }