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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> | |
da5e4ef7 | 23 | #include <linux/ramfs.h> |
2b2af54a | 24 | #include <linux/cred.h> |
e454cea2 | 25 | #include <linux/sched.h> |
2b2af54a | 26 | #include <linux/init_task.h> |
5a0e3ad6 | 27 | #include <linux/slab.h> |
2b2af54a KS |
28 | |
29 | static struct vfsmount *dev_mnt; | |
30 | ||
31 | #if defined CONFIG_DEVTMPFS_MOUNT | |
32 | static int dev_mount = 1; | |
33 | #else | |
34 | static int dev_mount; | |
35 | #endif | |
36 | ||
f1f76f86 | 37 | static DEFINE_MUTEX(dirlock); |
ed413ae6 | 38 | |
2b2af54a KS |
39 | static int __init mount_param(char *str) |
40 | { | |
41 | dev_mount = simple_strtoul(str, NULL, 0); | |
42 | return 1; | |
43 | } | |
44 | __setup("devtmpfs.mount=", mount_param); | |
45 | ||
46 | static int dev_get_sb(struct file_system_type *fs_type, int flags, | |
47 | const char *dev_name, void *data, struct vfsmount *mnt) | |
48 | { | |
da5e4ef7 | 49 | #ifdef CONFIG_TMPFS |
2b2af54a | 50 | return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt); |
da5e4ef7 PK |
51 | #else |
52 | return get_sb_single(fs_type, flags, data, ramfs_fill_super, mnt); | |
53 | #endif | |
2b2af54a KS |
54 | } |
55 | ||
56 | static struct file_system_type dev_fs_type = { | |
57 | .name = "devtmpfs", | |
58 | .get_sb = dev_get_sb, | |
59 | .kill_sb = kill_litter_super, | |
60 | }; | |
61 | ||
62 | #ifdef CONFIG_BLOCK | |
63 | static inline int is_blockdev(struct device *dev) | |
64 | { | |
65 | return dev->class == &block_class; | |
66 | } | |
67 | #else | |
68 | static inline int is_blockdev(struct device *dev) { return 0; } | |
69 | #endif | |
70 | ||
71 | static int dev_mkdir(const char *name, mode_t mode) | |
72 | { | |
73 | struct nameidata nd; | |
74 | struct dentry *dentry; | |
75 | int err; | |
76 | ||
77 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
78 | name, LOOKUP_PARENT, &nd); | |
79 | if (err) | |
80 | return err; | |
81 | ||
82 | dentry = lookup_create(&nd, 1); | |
83 | if (!IS_ERR(dentry)) { | |
84 | err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); | |
015bf43b KS |
85 | if (!err) |
86 | /* mark as kernel-created inode */ | |
87 | dentry->d_inode->i_private = &dev_mnt; | |
2b2af54a KS |
88 | dput(dentry); |
89 | } else { | |
90 | err = PTR_ERR(dentry); | |
91 | } | |
2b2af54a | 92 | |
015bf43b | 93 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
94 | path_put(&nd.path); |
95 | return err; | |
96 | } | |
97 | ||
98 | static int create_path(const char *nodepath) | |
99 | { | |
015bf43b | 100 | int err; |
2b2af54a | 101 | |
f1f76f86 | 102 | mutex_lock(&dirlock); |
015bf43b KS |
103 | err = dev_mkdir(nodepath, 0755); |
104 | if (err == -ENOENT) { | |
ed413ae6 | 105 | char *path; |
2b2af54a KS |
106 | char *s; |
107 | ||
108 | /* parent directories do not exist, create them */ | |
ed413ae6 | 109 | path = kstrdup(nodepath, GFP_KERNEL); |
80422738 KS |
110 | if (!path) { |
111 | err = -ENOMEM; | |
112 | goto out; | |
113 | } | |
2b2af54a | 114 | s = path; |
ed413ae6 | 115 | for (;;) { |
2b2af54a KS |
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 | } | |
ed413ae6 | 126 | kfree(path); |
2b2af54a | 127 | } |
80422738 | 128 | out: |
f1f76f86 | 129 | mutex_unlock(&dirlock); |
2b2af54a KS |
130 | return err; |
131 | } | |
132 | ||
133 | int devtmpfs_create_node(struct device *dev) | |
134 | { | |
135 | const char *tmp = NULL; | |
136 | const char *nodename; | |
137 | const struct cred *curr_cred; | |
e454cea2 | 138 | mode_t mode = 0; |
2b2af54a KS |
139 | struct nameidata nd; |
140 | struct dentry *dentry; | |
141 | int err; | |
142 | ||
143 | if (!dev_mnt) | |
144 | return 0; | |
145 | ||
e454cea2 | 146 | nodename = device_get_devnode(dev, &mode, &tmp); |
2b2af54a KS |
147 | if (!nodename) |
148 | return -ENOMEM; | |
149 | ||
e454cea2 KS |
150 | if (mode == 0) |
151 | mode = 0600; | |
2b2af54a | 152 | if (is_blockdev(dev)) |
e454cea2 | 153 | mode |= S_IFBLK; |
2b2af54a | 154 | else |
e454cea2 | 155 | mode |= S_IFCHR; |
2b2af54a KS |
156 | |
157 | curr_cred = override_creds(&init_cred); | |
00926996 | 158 | |
2b2af54a KS |
159 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
160 | nodename, LOOKUP_PARENT, &nd); | |
161 | if (err == -ENOENT) { | |
2b2af54a KS |
162 | create_path(nodename); |
163 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
164 | nodename, LOOKUP_PARENT, &nd); | |
2b2af54a | 165 | } |
00926996 KS |
166 | if (err) |
167 | goto out; | |
2b2af54a KS |
168 | |
169 | dentry = lookup_create(&nd, 0); | |
170 | if (!IS_ERR(dentry)) { | |
171 | err = vfs_mknod(nd.path.dentry->d_inode, | |
172 | dentry, mode, dev->devt); | |
00926996 KS |
173 | if (!err) { |
174 | struct iattr newattrs; | |
175 | ||
176 | /* fixup possibly umasked mode */ | |
177 | newattrs.ia_mode = mode; | |
178 | newattrs.ia_valid = ATTR_MODE; | |
179 | mutex_lock(&dentry->d_inode->i_mutex); | |
180 | notify_change(dentry, &newattrs); | |
181 | mutex_unlock(&dentry->d_inode->i_mutex); | |
182 | ||
183 | /* mark as kernel-created inode */ | |
2b2af54a | 184 | dentry->d_inode->i_private = &dev_mnt; |
00926996 | 185 | } |
2b2af54a KS |
186 | dput(dentry); |
187 | } else { | |
188 | err = PTR_ERR(dentry); | |
189 | } | |
2b2af54a | 190 | |
00926996 | 191 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
192 | path_put(&nd.path); |
193 | out: | |
194 | kfree(tmp); | |
195 | revert_creds(curr_cred); | |
196 | return err; | |
197 | } | |
198 | ||
199 | static int dev_rmdir(const char *name) | |
200 | { | |
201 | struct nameidata nd; | |
202 | struct dentry *dentry; | |
203 | int err; | |
204 | ||
205 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
206 | name, LOOKUP_PARENT, &nd); | |
207 | if (err) | |
208 | return err; | |
209 | ||
210 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
211 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
212 | if (!IS_ERR(dentry)) { | |
015bf43b KS |
213 | if (dentry->d_inode) { |
214 | if (dentry->d_inode->i_private == &dev_mnt) | |
215 | err = vfs_rmdir(nd.path.dentry->d_inode, | |
216 | dentry); | |
217 | else | |
218 | err = -EPERM; | |
219 | } else { | |
2b2af54a | 220 | err = -ENOENT; |
015bf43b | 221 | } |
2b2af54a KS |
222 | dput(dentry); |
223 | } else { | |
224 | err = PTR_ERR(dentry); | |
225 | } | |
2b2af54a | 226 | |
015bf43b | 227 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
228 | path_put(&nd.path); |
229 | return err; | |
230 | } | |
231 | ||
232 | static int delete_path(const char *nodepath) | |
233 | { | |
234 | const char *path; | |
235 | int err = 0; | |
236 | ||
237 | path = kstrdup(nodepath, GFP_KERNEL); | |
238 | if (!path) | |
239 | return -ENOMEM; | |
240 | ||
f1f76f86 | 241 | mutex_lock(&dirlock); |
ed413ae6 | 242 | for (;;) { |
2b2af54a KS |
243 | char *base; |
244 | ||
245 | base = strrchr(path, '/'); | |
246 | if (!base) | |
247 | break; | |
248 | base[0] = '\0'; | |
249 | err = dev_rmdir(path); | |
250 | if (err) | |
251 | break; | |
252 | } | |
f1f76f86 | 253 | mutex_unlock(&dirlock); |
2b2af54a KS |
254 | |
255 | kfree(path); | |
256 | return err; | |
257 | } | |
258 | ||
259 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
260 | { | |
261 | /* did we create it */ | |
262 | if (inode->i_private != &dev_mnt) | |
263 | return 0; | |
264 | ||
265 | /* does the dev_t match */ | |
266 | if (is_blockdev(dev)) { | |
267 | if (!S_ISBLK(stat->mode)) | |
268 | return 0; | |
269 | } else { | |
270 | if (!S_ISCHR(stat->mode)) | |
271 | return 0; | |
272 | } | |
273 | if (stat->rdev != dev->devt) | |
274 | return 0; | |
275 | ||
276 | /* ours */ | |
277 | return 1; | |
278 | } | |
279 | ||
280 | int devtmpfs_delete_node(struct device *dev) | |
281 | { | |
282 | const char *tmp = NULL; | |
283 | const char *nodename; | |
284 | const struct cred *curr_cred; | |
285 | struct nameidata nd; | |
286 | struct dentry *dentry; | |
287 | struct kstat stat; | |
288 | int deleted = 1; | |
289 | int err; | |
290 | ||
291 | if (!dev_mnt) | |
292 | return 0; | |
293 | ||
e454cea2 | 294 | nodename = device_get_devnode(dev, NULL, &tmp); |
2b2af54a KS |
295 | if (!nodename) |
296 | return -ENOMEM; | |
297 | ||
298 | curr_cred = override_creds(&init_cred); | |
299 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
300 | nodename, LOOKUP_PARENT, &nd); | |
301 | if (err) | |
302 | goto out; | |
303 | ||
304 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
305 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
306 | if (!IS_ERR(dentry)) { | |
307 | if (dentry->d_inode) { | |
308 | err = vfs_getattr(nd.path.mnt, dentry, &stat); | |
309 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { | |
5e31d76f KS |
310 | struct iattr newattrs; |
311 | /* | |
312 | * before unlinking this node, reset permissions | |
313 | * of possible references like hardlinks | |
314 | */ | |
315 | newattrs.ia_uid = 0; | |
316 | newattrs.ia_gid = 0; | |
317 | newattrs.ia_mode = stat.mode & ~0777; | |
318 | newattrs.ia_valid = | |
319 | ATTR_UID|ATTR_GID|ATTR_MODE; | |
320 | mutex_lock(&dentry->d_inode->i_mutex); | |
321 | notify_change(dentry, &newattrs); | |
322 | mutex_unlock(&dentry->d_inode->i_mutex); | |
2b2af54a KS |
323 | err = vfs_unlink(nd.path.dentry->d_inode, |
324 | dentry); | |
325 | if (!err || err == -ENOENT) | |
326 | deleted = 1; | |
327 | } | |
328 | } else { | |
329 | err = -ENOENT; | |
330 | } | |
331 | dput(dentry); | |
332 | } else { | |
333 | err = PTR_ERR(dentry); | |
334 | } | |
335 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
336 | ||
337 | path_put(&nd.path); | |
338 | if (deleted && strchr(nodename, '/')) | |
339 | delete_path(nodename); | |
340 | out: | |
341 | kfree(tmp); | |
342 | revert_creds(curr_cred); | |
343 | return err; | |
344 | } | |
345 | ||
346 | /* | |
347 | * If configured, or requested by the commandline, devtmpfs will be | |
348 | * auto-mounted after the kernel mounted the root filesystem. | |
349 | */ | |
073120cc | 350 | int devtmpfs_mount(const char *mntdir) |
2b2af54a | 351 | { |
2b2af54a KS |
352 | int err; |
353 | ||
354 | if (!dev_mount) | |
355 | return 0; | |
356 | ||
357 | if (!dev_mnt) | |
358 | return 0; | |
359 | ||
073120cc | 360 | err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); |
2b2af54a KS |
361 | if (err) |
362 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
363 | else | |
364 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
2b2af54a KS |
365 | return err; |
366 | } | |
367 | ||
368 | /* | |
369 | * Create devtmpfs instance, driver-core devices will add their device | |
370 | * nodes here. | |
371 | */ | |
372 | int __init devtmpfs_init(void) | |
373 | { | |
374 | int err; | |
375 | struct vfsmount *mnt; | |
f776c5ec | 376 | char options[] = "mode=0755"; |
2b2af54a KS |
377 | |
378 | err = register_filesystem(&dev_fs_type); | |
379 | if (err) { | |
380 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
381 | "type %i\n", err); | |
382 | return err; | |
383 | } | |
384 | ||
f776c5ec | 385 | mnt = kern_mount_data(&dev_fs_type, options); |
2b2af54a KS |
386 | if (IS_ERR(mnt)) { |
387 | err = PTR_ERR(mnt); | |
388 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); | |
389 | unregister_filesystem(&dev_fs_type); | |
390 | return err; | |
391 | } | |
392 | dev_mnt = mnt; | |
393 | ||
394 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
395 | return 0; | |
396 | } |