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2b2af54a KS |
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 | |
e454cea2 KS |
9 | * 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. | |
2b2af54a KS |
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/cred.h> | |
e454cea2 | 24 | #include <linux/sched.h> |
2b2af54a | 25 | #include <linux/init_task.h> |
5a0e3ad6 | 26 | #include <linux/slab.h> |
2b2af54a KS |
27 | |
28 | static struct vfsmount *dev_mnt; | |
29 | ||
30 | #if defined CONFIG_DEVTMPFS_MOUNT | |
31 | static int dev_mount = 1; | |
32 | #else | |
33 | static int dev_mount; | |
34 | #endif | |
35 | ||
f1f76f86 | 36 | static DEFINE_MUTEX(dirlock); |
ed413ae6 | 37 | |
2b2af54a KS |
38 | static int __init mount_param(char *str) |
39 | { | |
40 | dev_mount = simple_strtoul(str, NULL, 0); | |
41 | return 1; | |
42 | } | |
43 | __setup("devtmpfs.mount=", mount_param); | |
44 | ||
45 | static int dev_get_sb(struct file_system_type *fs_type, int flags, | |
46 | const char *dev_name, void *data, struct vfsmount *mnt) | |
47 | { | |
48 | return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt); | |
49 | } | |
50 | ||
51 | static struct file_system_type dev_fs_type = { | |
52 | .name = "devtmpfs", | |
53 | .get_sb = dev_get_sb, | |
54 | .kill_sb = kill_litter_super, | |
55 | }; | |
56 | ||
57 | #ifdef CONFIG_BLOCK | |
58 | static inline int is_blockdev(struct device *dev) | |
59 | { | |
60 | return dev->class == &block_class; | |
61 | } | |
62 | #else | |
63 | static inline int is_blockdev(struct device *dev) { return 0; } | |
64 | #endif | |
65 | ||
66 | static int dev_mkdir(const char *name, mode_t mode) | |
67 | { | |
68 | struct nameidata nd; | |
69 | struct dentry *dentry; | |
70 | int err; | |
71 | ||
72 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
73 | name, LOOKUP_PARENT, &nd); | |
74 | if (err) | |
75 | return err; | |
76 | ||
77 | dentry = lookup_create(&nd, 1); | |
78 | if (!IS_ERR(dentry)) { | |
79 | err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); | |
015bf43b KS |
80 | if (!err) |
81 | /* mark as kernel-created inode */ | |
82 | dentry->d_inode->i_private = &dev_mnt; | |
2b2af54a KS |
83 | dput(dentry); |
84 | } else { | |
85 | err = PTR_ERR(dentry); | |
86 | } | |
2b2af54a | 87 | |
015bf43b | 88 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
89 | path_put(&nd.path); |
90 | return err; | |
91 | } | |
92 | ||
93 | static int create_path(const char *nodepath) | |
94 | { | |
015bf43b | 95 | int err; |
2b2af54a | 96 | |
f1f76f86 | 97 | mutex_lock(&dirlock); |
015bf43b KS |
98 | err = dev_mkdir(nodepath, 0755); |
99 | if (err == -ENOENT) { | |
ed413ae6 | 100 | char *path; |
2b2af54a KS |
101 | char *s; |
102 | ||
103 | /* parent directories do not exist, create them */ | |
ed413ae6 | 104 | path = kstrdup(nodepath, GFP_KERNEL); |
80422738 KS |
105 | if (!path) { |
106 | err = -ENOMEM; | |
107 | goto out; | |
108 | } | |
2b2af54a | 109 | s = path; |
ed413ae6 | 110 | for (;;) { |
2b2af54a KS |
111 | s = strchr(s, '/'); |
112 | if (!s) | |
113 | break; | |
114 | s[0] = '\0'; | |
115 | err = dev_mkdir(path, 0755); | |
116 | if (err && err != -EEXIST) | |
117 | break; | |
118 | s[0] = '/'; | |
119 | s++; | |
120 | } | |
ed413ae6 | 121 | kfree(path); |
2b2af54a | 122 | } |
80422738 | 123 | out: |
f1f76f86 | 124 | mutex_unlock(&dirlock); |
2b2af54a KS |
125 | return err; |
126 | } | |
127 | ||
128 | int devtmpfs_create_node(struct device *dev) | |
129 | { | |
130 | const char *tmp = NULL; | |
131 | const char *nodename; | |
132 | const struct cred *curr_cred; | |
e454cea2 | 133 | mode_t mode = 0; |
2b2af54a KS |
134 | struct nameidata nd; |
135 | struct dentry *dentry; | |
136 | int err; | |
137 | ||
138 | if (!dev_mnt) | |
139 | return 0; | |
140 | ||
e454cea2 | 141 | nodename = device_get_devnode(dev, &mode, &tmp); |
2b2af54a KS |
142 | if (!nodename) |
143 | return -ENOMEM; | |
144 | ||
e454cea2 KS |
145 | if (mode == 0) |
146 | mode = 0600; | |
2b2af54a | 147 | if (is_blockdev(dev)) |
e454cea2 | 148 | mode |= S_IFBLK; |
2b2af54a | 149 | else |
e454cea2 | 150 | mode |= S_IFCHR; |
2b2af54a KS |
151 | |
152 | curr_cred = override_creds(&init_cred); | |
00926996 | 153 | |
2b2af54a KS |
154 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
155 | nodename, LOOKUP_PARENT, &nd); | |
156 | if (err == -ENOENT) { | |
2b2af54a KS |
157 | create_path(nodename); |
158 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
159 | nodename, LOOKUP_PARENT, &nd); | |
2b2af54a | 160 | } |
00926996 KS |
161 | if (err) |
162 | goto out; | |
2b2af54a KS |
163 | |
164 | dentry = lookup_create(&nd, 0); | |
165 | if (!IS_ERR(dentry)) { | |
166 | err = vfs_mknod(nd.path.dentry->d_inode, | |
167 | dentry, mode, dev->devt); | |
00926996 KS |
168 | if (!err) { |
169 | struct iattr newattrs; | |
170 | ||
171 | /* fixup possibly umasked mode */ | |
172 | newattrs.ia_mode = mode; | |
173 | newattrs.ia_valid = ATTR_MODE; | |
174 | mutex_lock(&dentry->d_inode->i_mutex); | |
175 | notify_change(dentry, &newattrs); | |
176 | mutex_unlock(&dentry->d_inode->i_mutex); | |
177 | ||
178 | /* mark as kernel-created inode */ | |
2b2af54a | 179 | dentry->d_inode->i_private = &dev_mnt; |
00926996 | 180 | } |
2b2af54a KS |
181 | dput(dentry); |
182 | } else { | |
183 | err = PTR_ERR(dentry); | |
184 | } | |
2b2af54a | 185 | |
00926996 | 186 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
187 | path_put(&nd.path); |
188 | out: | |
189 | kfree(tmp); | |
190 | revert_creds(curr_cred); | |
191 | return err; | |
192 | } | |
193 | ||
194 | static int dev_rmdir(const char *name) | |
195 | { | |
196 | struct nameidata nd; | |
197 | struct dentry *dentry; | |
198 | int err; | |
199 | ||
200 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
201 | name, LOOKUP_PARENT, &nd); | |
202 | if (err) | |
203 | return err; | |
204 | ||
205 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
206 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
207 | if (!IS_ERR(dentry)) { | |
015bf43b KS |
208 | if (dentry->d_inode) { |
209 | if (dentry->d_inode->i_private == &dev_mnt) | |
210 | err = vfs_rmdir(nd.path.dentry->d_inode, | |
211 | dentry); | |
212 | else | |
213 | err = -EPERM; | |
214 | } else { | |
2b2af54a | 215 | err = -ENOENT; |
015bf43b | 216 | } |
2b2af54a KS |
217 | dput(dentry); |
218 | } else { | |
219 | err = PTR_ERR(dentry); | |
220 | } | |
2b2af54a | 221 | |
015bf43b | 222 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
223 | path_put(&nd.path); |
224 | return err; | |
225 | } | |
226 | ||
227 | static int delete_path(const char *nodepath) | |
228 | { | |
229 | const char *path; | |
230 | int err = 0; | |
231 | ||
232 | path = kstrdup(nodepath, GFP_KERNEL); | |
233 | if (!path) | |
234 | return -ENOMEM; | |
235 | ||
f1f76f86 | 236 | mutex_lock(&dirlock); |
ed413ae6 | 237 | for (;;) { |
2b2af54a KS |
238 | char *base; |
239 | ||
240 | base = strrchr(path, '/'); | |
241 | if (!base) | |
242 | break; | |
243 | base[0] = '\0'; | |
244 | err = dev_rmdir(path); | |
245 | if (err) | |
246 | break; | |
247 | } | |
f1f76f86 | 248 | mutex_unlock(&dirlock); |
2b2af54a KS |
249 | |
250 | kfree(path); | |
251 | return err; | |
252 | } | |
253 | ||
254 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
255 | { | |
256 | /* did we create it */ | |
257 | if (inode->i_private != &dev_mnt) | |
258 | return 0; | |
259 | ||
260 | /* does the dev_t match */ | |
261 | if (is_blockdev(dev)) { | |
262 | if (!S_ISBLK(stat->mode)) | |
263 | return 0; | |
264 | } else { | |
265 | if (!S_ISCHR(stat->mode)) | |
266 | return 0; | |
267 | } | |
268 | if (stat->rdev != dev->devt) | |
269 | return 0; | |
270 | ||
271 | /* ours */ | |
272 | return 1; | |
273 | } | |
274 | ||
275 | int devtmpfs_delete_node(struct device *dev) | |
276 | { | |
277 | const char *tmp = NULL; | |
278 | const char *nodename; | |
279 | const struct cred *curr_cred; | |
280 | struct nameidata nd; | |
281 | struct dentry *dentry; | |
282 | struct kstat stat; | |
283 | int deleted = 1; | |
284 | int err; | |
285 | ||
286 | if (!dev_mnt) | |
287 | return 0; | |
288 | ||
e454cea2 | 289 | nodename = device_get_devnode(dev, NULL, &tmp); |
2b2af54a KS |
290 | if (!nodename) |
291 | return -ENOMEM; | |
292 | ||
293 | curr_cred = override_creds(&init_cred); | |
294 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
295 | nodename, LOOKUP_PARENT, &nd); | |
296 | if (err) | |
297 | goto out; | |
298 | ||
299 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
300 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
301 | if (!IS_ERR(dentry)) { | |
302 | if (dentry->d_inode) { | |
303 | err = vfs_getattr(nd.path.mnt, dentry, &stat); | |
304 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { | |
5e31d76f KS |
305 | struct iattr newattrs; |
306 | /* | |
307 | * before unlinking this node, reset permissions | |
308 | * of possible references like hardlinks | |
309 | */ | |
310 | newattrs.ia_uid = 0; | |
311 | newattrs.ia_gid = 0; | |
312 | newattrs.ia_mode = stat.mode & ~0777; | |
313 | newattrs.ia_valid = | |
314 | ATTR_UID|ATTR_GID|ATTR_MODE; | |
315 | mutex_lock(&dentry->d_inode->i_mutex); | |
316 | notify_change(dentry, &newattrs); | |
317 | mutex_unlock(&dentry->d_inode->i_mutex); | |
2b2af54a KS |
318 | err = vfs_unlink(nd.path.dentry->d_inode, |
319 | dentry); | |
320 | if (!err || err == -ENOENT) | |
321 | deleted = 1; | |
322 | } | |
323 | } else { | |
324 | err = -ENOENT; | |
325 | } | |
326 | dput(dentry); | |
327 | } else { | |
328 | err = PTR_ERR(dentry); | |
329 | } | |
330 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
331 | ||
332 | path_put(&nd.path); | |
333 | if (deleted && strchr(nodename, '/')) | |
334 | delete_path(nodename); | |
335 | out: | |
336 | kfree(tmp); | |
337 | revert_creds(curr_cred); | |
338 | return err; | |
339 | } | |
340 | ||
341 | /* | |
342 | * If configured, or requested by the commandline, devtmpfs will be | |
343 | * auto-mounted after the kernel mounted the root filesystem. | |
344 | */ | |
073120cc | 345 | int devtmpfs_mount(const char *mntdir) |
2b2af54a | 346 | { |
2b2af54a KS |
347 | int err; |
348 | ||
349 | if (!dev_mount) | |
350 | return 0; | |
351 | ||
352 | if (!dev_mnt) | |
353 | return 0; | |
354 | ||
073120cc | 355 | err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); |
2b2af54a KS |
356 | if (err) |
357 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
358 | else | |
359 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
2b2af54a KS |
360 | return err; |
361 | } | |
362 | ||
363 | /* | |
364 | * Create devtmpfs instance, driver-core devices will add their device | |
365 | * nodes here. | |
366 | */ | |
367 | int __init devtmpfs_init(void) | |
368 | { | |
369 | int err; | |
370 | struct vfsmount *mnt; | |
f776c5ec | 371 | char options[] = "mode=0755"; |
2b2af54a KS |
372 | |
373 | err = register_filesystem(&dev_fs_type); | |
374 | if (err) { | |
375 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
376 | "type %i\n", err); | |
377 | return err; | |
378 | } | |
379 | ||
f776c5ec | 380 | mnt = kern_mount_data(&dev_fs_type, options); |
2b2af54a KS |
381 | if (IS_ERR(mnt)) { |
382 | err = PTR_ERR(mnt); | |
383 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); | |
384 | unregister_filesystem(&dev_fs_type); | |
385 | return err; | |
386 | } | |
387 | dev_mnt = mnt; | |
388 | ||
389 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
390 | return 0; | |
391 | } |