blob: b89fffc1d777b277abd7bac4221b0fbc98e265ff [file] [log] [blame]
Kay Sievers2b2af542009-04-30 15:23:42 +02001/*
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
Kay Sieverse454cea2009-09-18 23:01:12 +02009 * filesystem.
10 * By default, all devices are named after the the name of the
11 * device, owned by root and have a default mode of 0600. Subsystems
12 * can overwrite the default setting if needed.
Kay Sievers2b2af542009-04-30 15:23:42 +020013 */
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>
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +010023#include <linux/ramfs.h>
Kay Sieverse454cea2009-09-18 23:01:12 +020024#include <linux/sched.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090025#include <linux/slab.h>
Al Viro2780f1f2011-06-27 16:25:29 -040026#include <linux/kthread.h>
Kay Sievers2b2af542009-04-30 15:23:42 +020027
Al Viro2780f1f2011-06-27 16:25:29 -040028static struct task_struct *thread;
Kay Sievers2b2af542009-04-30 15:23:42 +020029
30#if defined CONFIG_DEVTMPFS_MOUNT
Al Virofc14f2f2010-07-25 01:48:30 +040031static int mount_dev = 1;
Kay Sievers2b2af542009-04-30 15:23:42 +020032#else
Al Virofc14f2f2010-07-25 01:48:30 +040033static int mount_dev;
Kay Sievers2b2af542009-04-30 15:23:42 +020034#endif
35
Al Viro2780f1f2011-06-27 16:25:29 -040036static DEFINE_SPINLOCK(req_lock);
37
38static struct req {
39 struct req *next;
40 struct completion done;
41 int err;
42 const char *name;
43 mode_t mode; /* 0 => delete */
44 struct device *dev;
45} *requests;
Kay Sieversed413ae2009-10-28 19:51:06 +010046
Kay Sievers2b2af542009-04-30 15:23:42 +020047static int __init mount_param(char *str)
48{
Al Virofc14f2f2010-07-25 01:48:30 +040049 mount_dev = simple_strtoul(str, NULL, 0);
Kay Sievers2b2af542009-04-30 15:23:42 +020050 return 1;
51}
52__setup("devtmpfs.mount=", mount_param);
53
Al Virofc14f2f2010-07-25 01:48:30 +040054static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
55 const char *dev_name, void *data)
Kay Sievers2b2af542009-04-30 15:23:42 +020056{
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +010057#ifdef CONFIG_TMPFS
Al Virofc14f2f2010-07-25 01:48:30 +040058 return mount_single(fs_type, flags, data, shmem_fill_super);
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +010059#else
Al Virofc14f2f2010-07-25 01:48:30 +040060 return mount_single(fs_type, flags, data, ramfs_fill_super);
Peter Korsgaardda5e4ef2010-03-16 21:55:21 +010061#endif
Kay Sievers2b2af542009-04-30 15:23:42 +020062}
63
64static struct file_system_type dev_fs_type = {
65 .name = "devtmpfs",
Al Virofc14f2f2010-07-25 01:48:30 +040066 .mount = dev_mount,
Kay Sievers2b2af542009-04-30 15:23:42 +020067 .kill_sb = kill_litter_super,
68};
69
70#ifdef CONFIG_BLOCK
71static inline int is_blockdev(struct device *dev)
72{
73 return dev->class == &block_class;
74}
75#else
76static inline int is_blockdev(struct device *dev) { return 0; }
77#endif
78
Al Viro2780f1f2011-06-27 16:25:29 -040079int devtmpfs_create_node(struct device *dev)
80{
81 const char *tmp = NULL;
82 struct req req;
83
84 if (!thread)
85 return 0;
86
87 req.mode = 0;
88 req.name = device_get_devnode(dev, &req.mode, &tmp);
89 if (!req.name)
90 return -ENOMEM;
91
92 if (req.mode == 0)
93 req.mode = 0600;
94 if (is_blockdev(dev))
95 req.mode |= S_IFBLK;
96 else
97 req.mode |= S_IFCHR;
98
99 req.dev = dev;
100
101 init_completion(&req.done);
102
103 spin_lock(&req_lock);
104 req.next = requests;
105 requests = &req;
106 spin_unlock(&req_lock);
107
108 wake_up_process(thread);
109 wait_for_completion(&req.done);
110
111 kfree(tmp);
112
113 return req.err;
114}
115
116int devtmpfs_delete_node(struct device *dev)
117{
118 const char *tmp = NULL;
119 struct req req;
120
121 if (!thread)
122 return 0;
123
124 req.name = device_get_devnode(dev, NULL, &tmp);
125 if (!req.name)
126 return -ENOMEM;
127
128 req.mode = 0;
129 req.dev = dev;
130
131 init_completion(&req.done);
132
133 spin_lock(&req_lock);
134 req.next = requests;
135 requests = &req;
136 spin_unlock(&req_lock);
137
138 wake_up_process(thread);
139 wait_for_completion(&req.done);
140
141 kfree(tmp);
142 return req.err;
143}
144
Kay Sievers2b2af542009-04-30 15:23:42 +0200145static int dev_mkdir(const char *name, mode_t mode)
146{
Kay Sievers2b2af542009-04-30 15:23:42 +0200147 struct dentry *dentry;
Al Viro69753a02011-06-27 16:35:45 -0400148 struct path path;
Kay Sievers2b2af542009-04-30 15:23:42 +0200149 int err;
150
Al Viro69753a02011-06-27 16:35:45 -0400151 dentry = kern_path_create(AT_FDCWD, name, &path, 1);
152 if (IS_ERR(dentry))
153 return PTR_ERR(dentry);
Kay Sievers2b2af542009-04-30 15:23:42 +0200154
Al Viro69753a02011-06-27 16:35:45 -0400155 err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
156 if (!err)
157 /* mark as kernel-created inode */
158 dentry->d_inode->i_private = &thread;
159 dput(dentry);
160 mutex_unlock(&path.dentry->d_inode->i_mutex);
161 path_put(&path);
Kay Sievers2b2af542009-04-30 15:23:42 +0200162 return err;
163}
164
165static int create_path(const char *nodepath)
166{
Al Viro5da4e682011-06-27 16:37:12 -0400167 char *path;
168 char *s;
Kay Sievers015bf432009-10-28 19:51:26 +0100169 int err;
Kay Sievers2b2af542009-04-30 15:23:42 +0200170
Al Viro5da4e682011-06-27 16:37:12 -0400171 /* parent directories do not exist, create them */
172 path = kstrdup(nodepath, GFP_KERNEL);
173 if (!path)
174 return -ENOMEM;
Kay Sievers2b2af542009-04-30 15:23:42 +0200175
Al Viro5da4e682011-06-27 16:37:12 -0400176 s = path;
177 for (;;) {
178 s = strchr(s, '/');
179 if (!s)
180 break;
181 s[0] = '\0';
182 err = dev_mkdir(path, 0755);
183 if (err && err != -EEXIST)
184 break;
185 s[0] = '/';
186 s++;
Kay Sievers2b2af542009-04-30 15:23:42 +0200187 }
Al Viro5da4e682011-06-27 16:37:12 -0400188 kfree(path);
Kay Sievers2b2af542009-04-30 15:23:42 +0200189 return err;
190}
191
Al Viro2780f1f2011-06-27 16:25:29 -0400192static int handle_create(const char *nodename, mode_t mode, struct device *dev)
Kay Sievers2b2af542009-04-30 15:23:42 +0200193{
Kay Sievers2b2af542009-04-30 15:23:42 +0200194 struct dentry *dentry;
Al Viro69753a02011-06-27 16:35:45 -0400195 struct path path;
Kay Sievers2b2af542009-04-30 15:23:42 +0200196 int err;
197
Al Viro69753a02011-06-27 16:35:45 -0400198 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
199 if (dentry == ERR_PTR(-ENOENT)) {
Kay Sievers2b2af542009-04-30 15:23:42 +0200200 create_path(nodename);
Al Viro69753a02011-06-27 16:35:45 -0400201 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
Kay Sievers2b2af542009-04-30 15:23:42 +0200202 }
Al Viro69753a02011-06-27 16:35:45 -0400203 if (IS_ERR(dentry))
204 return PTR_ERR(dentry);
Kay Sievers2b2af542009-04-30 15:23:42 +0200205
Al Viro69753a02011-06-27 16:35:45 -0400206 err = vfs_mknod(path.dentry->d_inode,
207 dentry, mode, dev->devt);
208 if (!err) {
209 struct iattr newattrs;
Kay Sievers00926992009-10-28 19:50:57 +0100210
Al Viro69753a02011-06-27 16:35:45 -0400211 /* fixup possibly umasked mode */
212 newattrs.ia_mode = mode;
213 newattrs.ia_valid = ATTR_MODE;
214 mutex_lock(&dentry->d_inode->i_mutex);
215 notify_change(dentry, &newattrs);
216 mutex_unlock(&dentry->d_inode->i_mutex);
Kay Sievers00926992009-10-28 19:50:57 +0100217
Al Viro69753a02011-06-27 16:35:45 -0400218 /* mark as kernel-created inode */
219 dentry->d_inode->i_private = &thread;
Kay Sievers2b2af542009-04-30 15:23:42 +0200220 }
Al Viro69753a02011-06-27 16:35:45 -0400221 dput(dentry);
Kay Sievers2b2af542009-04-30 15:23:42 +0200222
Al Viro69753a02011-06-27 16:35:45 -0400223 mutex_unlock(&path.dentry->d_inode->i_mutex);
224 path_put(&path);
Kay Sievers2b2af542009-04-30 15:23:42 +0200225 return err;
226}
227
228static int dev_rmdir(const char *name)
229{
230 struct nameidata nd;
231 struct dentry *dentry;
232 int err;
233
Al Viro2780f1f2011-06-27 16:25:29 -0400234 err = kern_path_parent(name, &nd);
Kay Sievers2b2af542009-04-30 15:23:42 +0200235 if (err)
236 return err;
237
238 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
239 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
240 if (!IS_ERR(dentry)) {
Kay Sievers015bf432009-10-28 19:51:26 +0100241 if (dentry->d_inode) {
Al Viro2780f1f2011-06-27 16:25:29 -0400242 if (dentry->d_inode->i_private == &thread)
Kay Sievers015bf432009-10-28 19:51:26 +0100243 err = vfs_rmdir(nd.path.dentry->d_inode,
244 dentry);
245 else
246 err = -EPERM;
247 } else {
Kay Sievers2b2af542009-04-30 15:23:42 +0200248 err = -ENOENT;
Kay Sievers015bf432009-10-28 19:51:26 +0100249 }
Kay Sievers2b2af542009-04-30 15:23:42 +0200250 dput(dentry);
251 } else {
252 err = PTR_ERR(dentry);
253 }
Kay Sievers2b2af542009-04-30 15:23:42 +0200254
Kay Sievers015bf432009-10-28 19:51:26 +0100255 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
Kay Sievers2b2af542009-04-30 15:23:42 +0200256 path_put(&nd.path);
257 return err;
258}
259
260static int delete_path(const char *nodepath)
261{
262 const char *path;
263 int err = 0;
264
265 path = kstrdup(nodepath, GFP_KERNEL);
266 if (!path)
267 return -ENOMEM;
268
Kay Sieversed413ae2009-10-28 19:51:06 +0100269 for (;;) {
Kay Sievers2b2af542009-04-30 15:23:42 +0200270 char *base;
271
272 base = strrchr(path, '/');
273 if (!base)
274 break;
275 base[0] = '\0';
276 err = dev_rmdir(path);
277 if (err)
278 break;
279 }
280
281 kfree(path);
282 return err;
283}
284
285static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
286{
287 /* did we create it */
Al Viro2780f1f2011-06-27 16:25:29 -0400288 if (inode->i_private != &thread)
Kay Sievers2b2af542009-04-30 15:23:42 +0200289 return 0;
290
291 /* does the dev_t match */
292 if (is_blockdev(dev)) {
293 if (!S_ISBLK(stat->mode))
294 return 0;
295 } else {
296 if (!S_ISCHR(stat->mode))
297 return 0;
298 }
299 if (stat->rdev != dev->devt)
300 return 0;
301
302 /* ours */
303 return 1;
304}
305
Al Viro2780f1f2011-06-27 16:25:29 -0400306static int handle_remove(const char *nodename, struct device *dev)
Kay Sievers2b2af542009-04-30 15:23:42 +0200307{
Kay Sievers2b2af542009-04-30 15:23:42 +0200308 struct nameidata nd;
309 struct dentry *dentry;
310 struct kstat stat;
311 int deleted = 1;
312 int err;
313
Al Viro2780f1f2011-06-27 16:25:29 -0400314 err = kern_path_parent(nodename, &nd);
Kay Sievers2b2af542009-04-30 15:23:42 +0200315 if (err)
Al Viro2780f1f2011-06-27 16:25:29 -0400316 return err;
Kay Sievers2b2af542009-04-30 15:23:42 +0200317
318 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
319 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
320 if (!IS_ERR(dentry)) {
321 if (dentry->d_inode) {
322 err = vfs_getattr(nd.path.mnt, dentry, &stat);
323 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
Kay Sievers5e31d762010-01-13 14:16:36 +0100324 struct iattr newattrs;
325 /*
326 * before unlinking this node, reset permissions
327 * of possible references like hardlinks
328 */
329 newattrs.ia_uid = 0;
330 newattrs.ia_gid = 0;
331 newattrs.ia_mode = stat.mode & ~0777;
332 newattrs.ia_valid =
333 ATTR_UID|ATTR_GID|ATTR_MODE;
334 mutex_lock(&dentry->d_inode->i_mutex);
335 notify_change(dentry, &newattrs);
336 mutex_unlock(&dentry->d_inode->i_mutex);
Kay Sievers2b2af542009-04-30 15:23:42 +0200337 err = vfs_unlink(nd.path.dentry->d_inode,
338 dentry);
339 if (!err || err == -ENOENT)
340 deleted = 1;
341 }
342 } else {
343 err = -ENOENT;
344 }
345 dput(dentry);
346 } else {
347 err = PTR_ERR(dentry);
348 }
349 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
350
351 path_put(&nd.path);
352 if (deleted && strchr(nodename, '/'))
353 delete_path(nodename);
Kay Sievers2b2af542009-04-30 15:23:42 +0200354 return err;
355}
356
357/*
358 * If configured, or requested by the commandline, devtmpfs will be
359 * auto-mounted after the kernel mounted the root filesystem.
360 */
Kay Sievers073120c2009-10-28 19:51:17 +0100361int devtmpfs_mount(const char *mntdir)
Kay Sievers2b2af542009-04-30 15:23:42 +0200362{
Kay Sievers2b2af542009-04-30 15:23:42 +0200363 int err;
364
Al Virofc14f2f2010-07-25 01:48:30 +0400365 if (!mount_dev)
Kay Sievers2b2af542009-04-30 15:23:42 +0200366 return 0;
367
Al Viro2780f1f2011-06-27 16:25:29 -0400368 if (!thread)
Kay Sievers2b2af542009-04-30 15:23:42 +0200369 return 0;
370
Kay Sievers073120c2009-10-28 19:51:17 +0100371 err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
Kay Sievers2b2af542009-04-30 15:23:42 +0200372 if (err)
373 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
374 else
375 printk(KERN_INFO "devtmpfs: mounted\n");
Kay Sievers2b2af542009-04-30 15:23:42 +0200376 return err;
377}
378
Al Viro2780f1f2011-06-27 16:25:29 -0400379static __initdata DECLARE_COMPLETION(setup_done);
380
381static int handle(const char *name, mode_t mode, struct device *dev)
382{
383 if (mode)
384 return handle_create(name, mode, dev);
385 else
386 return handle_remove(name, dev);
387}
388
389static int devtmpfsd(void *p)
390{
391 char options[] = "mode=0755";
392 int *err = p;
393 *err = sys_unshare(CLONE_NEWNS);
394 if (*err)
395 goto out;
396 *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
397 if (*err)
398 goto out;
399 sys_chdir("/.."); /* will traverse into overmounted root */
400 sys_chroot(".");
401 complete(&setup_done);
402 while (1) {
403 spin_lock(&req_lock);
404 while (requests) {
405 struct req *req = requests;
406 requests = NULL;
407 spin_unlock(&req_lock);
408 while (req) {
Al Viroe13889b2011-07-25 14:15:50 -0400409 struct req *next = req->next;
Al Viro2780f1f2011-06-27 16:25:29 -0400410 req->err = handle(req->name, req->mode, req->dev);
411 complete(&req->done);
Al Viroe13889b2011-07-25 14:15:50 -0400412 req = next;
Al Viro2780f1f2011-06-27 16:25:29 -0400413 }
414 spin_lock(&req_lock);
415 }
416 set_current_state(TASK_INTERRUPTIBLE);
417 spin_unlock(&req_lock);
418 schedule();
419 __set_current_state(TASK_RUNNING);
420 }
421 return 0;
422out:
423 complete(&setup_done);
424 return *err;
425}
426
Kay Sievers2b2af542009-04-30 15:23:42 +0200427/*
428 * Create devtmpfs instance, driver-core devices will add their device
429 * nodes here.
430 */
431int __init devtmpfs_init(void)
432{
Al Viro2780f1f2011-06-27 16:25:29 -0400433 int err = register_filesystem(&dev_fs_type);
Kay Sievers2b2af542009-04-30 15:23:42 +0200434 if (err) {
435 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
436 "type %i\n", err);
437 return err;
438 }
439
Al Viro2780f1f2011-06-27 16:25:29 -0400440 thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
441 if (!IS_ERR(thread)) {
442 wait_for_completion(&setup_done);
443 } else {
444 err = PTR_ERR(thread);
445 thread = NULL;
446 }
447
448 if (err) {
Kay Sievers2b2af542009-04-30 15:23:42 +0200449 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
450 unregister_filesystem(&dev_fs_type);
451 return err;
452 }
Kay Sievers2b2af542009-04-30 15:23:42 +0200453
454 printk(KERN_INFO "devtmpfs: initialized\n");
455 return 0;
456}