[go: nahoru, domu]
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#include "base.h"
28
29static struct task_struct *thread;
30
31#if defined CONFIG_DEVTMPFS_MOUNT
32static int mount_dev = 1;
33#else
34static int mount_dev;
35#endif
36
37static DEFINE_SPINLOCK(req_lock);
38
39static struct req {
40	struct req *next;
41	struct completion done;
42	int err;
43	const char *name;
44	umode_t mode;	/* 0 => delete */
45	kuid_t uid;
46	kgid_t gid;
47	struct device *dev;
48} *requests;
49
50static int __init mount_param(char *str)
51{
52	mount_dev = simple_strtoul(str, NULL, 0);
53	return 1;
54}
55__setup("devtmpfs.mount=", mount_param);
56
57static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
58		      const char *dev_name, void *data)
59{
60#ifdef CONFIG_TMPFS
61	return mount_single(fs_type, flags, data, shmem_fill_super);
62#else
63	return mount_single(fs_type, flags, data, ramfs_fill_super);
64#endif
65}
66
67static struct file_system_type dev_fs_type = {
68	.name = "devtmpfs",
69	.mount = dev_mount,
70	.kill_sb = kill_litter_super,
71};
72
73#ifdef CONFIG_BLOCK
74static inline int is_blockdev(struct device *dev)
75{
76	return dev->class == &block_class;
77}
78#else
79static inline int is_blockdev(struct device *dev) { return 0; }
80#endif
81
82int devtmpfs_create_node(struct device *dev)
83{
84	const char *tmp = NULL;
85	struct req req;
86
87	if (!thread)
88		return 0;
89
90	req.mode = 0;
91	req.uid = GLOBAL_ROOT_UID;
92	req.gid = GLOBAL_ROOT_GID;
93	req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
94	if (!req.name)
95		return -ENOMEM;
96
97	if (req.mode == 0)
98		req.mode = 0600;
99	if (is_blockdev(dev))
100		req.mode |= S_IFBLK;
101	else
102		req.mode |= S_IFCHR;
103
104	req.dev = dev;
105
106	init_completion(&req.done);
107
108	spin_lock(&req_lock);
109	req.next = requests;
110	requests = &req;
111	spin_unlock(&req_lock);
112
113	wake_up_process(thread);
114	wait_for_completion(&req.done);
115
116	kfree(tmp);
117
118	return req.err;
119}
120
121int devtmpfs_delete_node(struct device *dev)
122{
123	const char *tmp = NULL;
124	struct req req;
125
126	if (!thread)
127		return 0;
128
129	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
130	if (!req.name)
131		return -ENOMEM;
132
133	req.mode = 0;
134	req.dev = dev;
135
136	init_completion(&req.done);
137
138	spin_lock(&req_lock);
139	req.next = requests;
140	requests = &req;
141	spin_unlock(&req_lock);
142
143	wake_up_process(thread);
144	wait_for_completion(&req.done);
145
146	kfree(tmp);
147	return req.err;
148}
149
150static int dev_mkdir(const char *name, umode_t mode)
151{
152	struct dentry *dentry;
153	struct path path;
154	int err;
155
156	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
157	if (IS_ERR(dentry))
158		return PTR_ERR(dentry);
159
160	err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
161	if (!err)
162		/* mark as kernel-created inode */
163		dentry->d_inode->i_private = &thread;
164	done_path_create(&path, dentry);
165	return err;
166}
167
168static int create_path(const char *nodepath)
169{
170	char *path;
171	char *s;
172	int err = 0;
173
174	/* parent directories do not exist, create them */
175	path = kstrdup(nodepath, GFP_KERNEL);
176	if (!path)
177		return -ENOMEM;
178
179	s = path;
180	for (;;) {
181		s = strchr(s, '/');
182		if (!s)
183			break;
184		s[0] = '\0';
185		err = dev_mkdir(path, 0755);
186		if (err && err != -EEXIST)
187			break;
188		s[0] = '/';
189		s++;
190	}
191	kfree(path);
192	return err;
193}
194
195static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
196			 kgid_t gid, struct device *dev)
197{
198	struct dentry *dentry;
199	struct path path;
200	int err;
201
202	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
203	if (dentry == ERR_PTR(-ENOENT)) {
204		create_path(nodename);
205		dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
206	}
207	if (IS_ERR(dentry))
208		return PTR_ERR(dentry);
209
210	err = vfs_mknod(path.dentry->d_inode, dentry, mode, dev->devt);
211	if (!err) {
212		struct iattr newattrs;
213
214		newattrs.ia_mode = mode;
215		newattrs.ia_uid = uid;
216		newattrs.ia_gid = gid;
217		newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
218		mutex_lock(&dentry->d_inode->i_mutex);
219		notify_change(dentry, &newattrs, NULL);
220		mutex_unlock(&dentry->d_inode->i_mutex);
221
222		/* mark as kernel-created inode */
223		dentry->d_inode->i_private = &thread;
224	}
225	done_path_create(&path, dentry);
226	return err;
227}
228
229static int dev_rmdir(const char *name)
230{
231	struct path parent;
232	struct dentry *dentry;
233	int err;
234
235	dentry = kern_path_locked(name, &parent);
236	if (IS_ERR(dentry))
237		return PTR_ERR(dentry);
238	if (dentry->d_inode) {
239		if (dentry->d_inode->i_private == &thread)
240			err = vfs_rmdir(parent.dentry->d_inode, dentry);
241		else
242			err = -EPERM;
243	} else {
244		err = -ENOENT;
245	}
246	dput(dentry);
247	mutex_unlock(&parent.dentry->d_inode->i_mutex);
248	path_put(&parent);
249	return err;
250}
251
252static int delete_path(const char *nodepath)
253{
254	const char *path;
255	int err = 0;
256
257	path = kstrdup(nodepath, GFP_KERNEL);
258	if (!path)
259		return -ENOMEM;
260
261	for (;;) {
262		char *base;
263
264		base = strrchr(path, '/');
265		if (!base)
266			break;
267		base[0] = '\0';
268		err = dev_rmdir(path);
269		if (err)
270			break;
271	}
272
273	kfree(path);
274	return err;
275}
276
277static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
278{
279	/* did we create it */
280	if (inode->i_private != &thread)
281		return 0;
282
283	/* does the dev_t match */
284	if (is_blockdev(dev)) {
285		if (!S_ISBLK(stat->mode))
286			return 0;
287	} else {
288		if (!S_ISCHR(stat->mode))
289			return 0;
290	}
291	if (stat->rdev != dev->devt)
292		return 0;
293
294	/* ours */
295	return 1;
296}
297
298static int handle_remove(const char *nodename, struct device *dev)
299{
300	struct path parent;
301	struct dentry *dentry;
302	int deleted = 0;
303	int err;
304
305	dentry = kern_path_locked(nodename, &parent);
306	if (IS_ERR(dentry))
307		return PTR_ERR(dentry);
308
309	if (dentry->d_inode) {
310		struct kstat stat;
311		struct path p = {.mnt = parent.mnt, .dentry = dentry};
312		err = vfs_getattr(&p, &stat);
313		if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
314			struct iattr newattrs;
315			/*
316			 * before unlinking this node, reset permissions
317			 * of possible references like hardlinks
318			 */
319			newattrs.ia_uid = GLOBAL_ROOT_UID;
320			newattrs.ia_gid = GLOBAL_ROOT_GID;
321			newattrs.ia_mode = stat.mode & ~0777;
322			newattrs.ia_valid =
323				ATTR_UID|ATTR_GID|ATTR_MODE;
324			mutex_lock(&dentry->d_inode->i_mutex);
325			notify_change(dentry, &newattrs, NULL);
326			mutex_unlock(&dentry->d_inode->i_mutex);
327			err = vfs_unlink(parent.dentry->d_inode, dentry, NULL);
328			if (!err || err == -ENOENT)
329				deleted = 1;
330		}
331	} else {
332		err = -ENOENT;
333	}
334	dput(dentry);
335	mutex_unlock(&parent.dentry->d_inode->i_mutex);
336
337	path_put(&parent);
338	if (deleted && strchr(nodename, '/'))
339		delete_path(nodename);
340	return err;
341}
342
343/*
344 * If configured, or requested by the commandline, devtmpfs will be
345 * auto-mounted after the kernel mounted the root filesystem.
346 */
347int devtmpfs_mount(const char *mntdir)
348{
349	int err;
350
351	if (!mount_dev)
352		return 0;
353
354	if (!thread)
355		return 0;
356
357	err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
358	if (err)
359		printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
360	else
361		printk(KERN_INFO "devtmpfs: mounted\n");
362	return err;
363}
364
365static DECLARE_COMPLETION(setup_done);
366
367static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
368		  struct device *dev)
369{
370	if (mode)
371		return handle_create(name, mode, uid, gid, dev);
372	else
373		return handle_remove(name, dev);
374}
375
376static int devtmpfsd(void *p)
377{
378	char options[] = "mode=0755";
379	int *err = p;
380	*err = sys_unshare(CLONE_NEWNS);
381	if (*err)
382		goto out;
383	*err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
384	if (*err)
385		goto out;
386	sys_chdir("/.."); /* will traverse into overmounted root */
387	sys_chroot(".");
388	complete(&setup_done);
389	while (1) {
390		spin_lock(&req_lock);
391		while (requests) {
392			struct req *req = requests;
393			requests = NULL;
394			spin_unlock(&req_lock);
395			while (req) {
396				struct req *next = req->next;
397				req->err = handle(req->name, req->mode,
398						  req->uid, req->gid, req->dev);
399				complete(&req->done);
400				req = next;
401			}
402			spin_lock(&req_lock);
403		}
404		__set_current_state(TASK_INTERRUPTIBLE);
405		spin_unlock(&req_lock);
406		schedule();
407	}
408	return 0;
409out:
410	complete(&setup_done);
411	return *err;
412}
413
414/*
415 * Create devtmpfs instance, driver-core devices will add their device
416 * nodes here.
417 */
418int __init devtmpfs_init(void)
419{
420	int err = register_filesystem(&dev_fs_type);
421	if (err) {
422		printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
423		       "type %i\n", err);
424		return err;
425	}
426
427	thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
428	if (!IS_ERR(thread)) {
429		wait_for_completion(&setup_done);
430	} else {
431		err = PTR_ERR(thread);
432		thread = NULL;
433	}
434
435	if (err) {
436		printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
437		unregister_filesystem(&dev_fs_type);
438		return err;
439	}
440
441	printk(KERN_INFO "devtmpfs: initialized\n");
442	return 0;
443}
444