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