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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 | ||
35 | static int __init mount_param(char *str) | |
36 | { | |
37 | dev_mount = simple_strtoul(str, NULL, 0); | |
38 | return 1; | |
39 | } | |
40 | __setup("devtmpfs.mount=", mount_param); | |
41 | ||
42 | static int dev_get_sb(struct file_system_type *fs_type, int flags, | |
43 | const char *dev_name, void *data, struct vfsmount *mnt) | |
44 | { | |
45 | return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt); | |
46 | } | |
47 | ||
48 | static struct file_system_type dev_fs_type = { | |
49 | .name = "devtmpfs", | |
50 | .get_sb = dev_get_sb, | |
51 | .kill_sb = kill_litter_super, | |
52 | }; | |
53 | ||
54 | #ifdef CONFIG_BLOCK | |
55 | static inline int is_blockdev(struct device *dev) | |
56 | { | |
57 | return dev->class == &block_class; | |
58 | } | |
59 | #else | |
60 | static inline int is_blockdev(struct device *dev) { return 0; } | |
61 | #endif | |
62 | ||
63 | static int dev_mkdir(const char *name, mode_t mode) | |
64 | { | |
65 | struct nameidata nd; | |
66 | struct dentry *dentry; | |
67 | int err; | |
68 | ||
69 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
70 | name, LOOKUP_PARENT, &nd); | |
71 | if (err) | |
72 | return err; | |
73 | ||
74 | dentry = lookup_create(&nd, 1); | |
75 | if (!IS_ERR(dentry)) { | |
76 | err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); | |
77 | dput(dentry); | |
78 | } else { | |
79 | err = PTR_ERR(dentry); | |
80 | } | |
81 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
82 | ||
83 | path_put(&nd.path); | |
84 | return err; | |
85 | } | |
86 | ||
87 | static int create_path(const char *nodepath) | |
88 | { | |
89 | char *path; | |
90 | struct nameidata nd; | |
91 | int err = 0; | |
92 | ||
93 | path = kstrdup(nodepath, GFP_KERNEL); | |
94 | if (!path) | |
95 | return -ENOMEM; | |
96 | ||
97 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
98 | path, LOOKUP_PARENT, &nd); | |
99 | if (err == 0) { | |
100 | struct dentry *dentry; | |
101 | ||
102 | /* create directory right away */ | |
103 | dentry = lookup_create(&nd, 1); | |
104 | if (!IS_ERR(dentry)) { | |
105 | err = vfs_mkdir(nd.path.dentry->d_inode, | |
106 | dentry, 0755); | |
107 | dput(dentry); | |
108 | } | |
109 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
110 | ||
111 | path_put(&nd.path); | |
112 | } else if (err == -ENOENT) { | |
113 | char *s; | |
114 | ||
115 | /* parent directories do not exist, create them */ | |
116 | s = path; | |
117 | while (1) { | |
118 | s = strchr(s, '/'); | |
119 | if (!s) | |
120 | break; | |
121 | s[0] = '\0'; | |
122 | err = dev_mkdir(path, 0755); | |
123 | if (err && err != -EEXIST) | |
124 | break; | |
125 | s[0] = '/'; | |
126 | s++; | |
127 | } | |
128 | } | |
129 | ||
130 | kfree(path); | |
131 | return err; | |
132 | } | |
133 | ||
134 | int devtmpfs_create_node(struct device *dev) | |
135 | { | |
136 | const char *tmp = NULL; | |
137 | const char *nodename; | |
138 | const struct cred *curr_cred; | |
e454cea2 | 139 | mode_t mode = 0; |
2b2af54a KS |
140 | struct nameidata nd; |
141 | struct dentry *dentry; | |
142 | int err; | |
143 | ||
144 | if (!dev_mnt) | |
145 | return 0; | |
146 | ||
e454cea2 | 147 | nodename = device_get_devnode(dev, &mode, &tmp); |
2b2af54a KS |
148 | if (!nodename) |
149 | return -ENOMEM; | |
150 | ||
e454cea2 KS |
151 | if (mode == 0) |
152 | mode = 0600; | |
2b2af54a | 153 | if (is_blockdev(dev)) |
e454cea2 | 154 | mode |= S_IFBLK; |
2b2af54a | 155 | else |
e454cea2 | 156 | mode |= S_IFCHR; |
2b2af54a KS |
157 | |
158 | curr_cred = override_creds(&init_cred); | |
159 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
160 | nodename, LOOKUP_PARENT, &nd); | |
161 | if (err == -ENOENT) { | |
162 | /* create missing parent directories */ | |
163 | create_path(nodename); | |
164 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
165 | nodename, LOOKUP_PARENT, &nd); | |
166 | if (err) | |
167 | goto out; | |
168 | } | |
169 | ||
170 | dentry = lookup_create(&nd, 0); | |
171 | if (!IS_ERR(dentry)) { | |
e454cea2 KS |
172 | int umask; |
173 | ||
174 | umask = sys_umask(0000); | |
2b2af54a KS |
175 | err = vfs_mknod(nd.path.dentry->d_inode, |
176 | dentry, mode, dev->devt); | |
e454cea2 | 177 | sys_umask(umask); |
2b2af54a KS |
178 | /* mark as kernel created inode */ |
179 | if (!err) | |
180 | dentry->d_inode->i_private = &dev_mnt; | |
181 | dput(dentry); | |
182 | } else { | |
183 | err = PTR_ERR(dentry); | |
184 | } | |
185 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
186 | ||
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)) { | |
208 | if (dentry->d_inode) | |
209 | err = vfs_rmdir(nd.path.dentry->d_inode, dentry); | |
210 | else | |
211 | err = -ENOENT; | |
212 | dput(dentry); | |
213 | } else { | |
214 | err = PTR_ERR(dentry); | |
215 | } | |
216 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
217 | ||
218 | path_put(&nd.path); | |
219 | return err; | |
220 | } | |
221 | ||
222 | static int delete_path(const char *nodepath) | |
223 | { | |
224 | const char *path; | |
225 | int err = 0; | |
226 | ||
227 | path = kstrdup(nodepath, GFP_KERNEL); | |
228 | if (!path) | |
229 | return -ENOMEM; | |
230 | ||
231 | while (1) { | |
232 | char *base; | |
233 | ||
234 | base = strrchr(path, '/'); | |
235 | if (!base) | |
236 | break; | |
237 | base[0] = '\0'; | |
238 | err = dev_rmdir(path); | |
239 | if (err) | |
240 | break; | |
241 | } | |
242 | ||
243 | kfree(path); | |
244 | return err; | |
245 | } | |
246 | ||
247 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
248 | { | |
249 | /* did we create it */ | |
250 | if (inode->i_private != &dev_mnt) | |
251 | return 0; | |
252 | ||
253 | /* does the dev_t match */ | |
254 | if (is_blockdev(dev)) { | |
255 | if (!S_ISBLK(stat->mode)) | |
256 | return 0; | |
257 | } else { | |
258 | if (!S_ISCHR(stat->mode)) | |
259 | return 0; | |
260 | } | |
261 | if (stat->rdev != dev->devt) | |
262 | return 0; | |
263 | ||
264 | /* ours */ | |
265 | return 1; | |
266 | } | |
267 | ||
268 | int devtmpfs_delete_node(struct device *dev) | |
269 | { | |
270 | const char *tmp = NULL; | |
271 | const char *nodename; | |
272 | const struct cred *curr_cred; | |
273 | struct nameidata nd; | |
274 | struct dentry *dentry; | |
275 | struct kstat stat; | |
276 | int deleted = 1; | |
277 | int err; | |
278 | ||
279 | if (!dev_mnt) | |
280 | return 0; | |
281 | ||
e454cea2 | 282 | nodename = device_get_devnode(dev, NULL, &tmp); |
2b2af54a KS |
283 | if (!nodename) |
284 | return -ENOMEM; | |
285 | ||
286 | curr_cred = override_creds(&init_cred); | |
287 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
288 | nodename, LOOKUP_PARENT, &nd); | |
289 | if (err) | |
290 | goto out; | |
291 | ||
292 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
293 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
294 | if (!IS_ERR(dentry)) { | |
295 | if (dentry->d_inode) { | |
296 | err = vfs_getattr(nd.path.mnt, dentry, &stat); | |
297 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { | |
298 | err = vfs_unlink(nd.path.dentry->d_inode, | |
299 | dentry); | |
300 | if (!err || err == -ENOENT) | |
301 | deleted = 1; | |
302 | } | |
303 | } else { | |
304 | err = -ENOENT; | |
305 | } | |
306 | dput(dentry); | |
307 | } else { | |
308 | err = PTR_ERR(dentry); | |
309 | } | |
310 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
311 | ||
312 | path_put(&nd.path); | |
313 | if (deleted && strchr(nodename, '/')) | |
314 | delete_path(nodename); | |
315 | out: | |
316 | kfree(tmp); | |
317 | revert_creds(curr_cred); | |
318 | return err; | |
319 | } | |
320 | ||
321 | /* | |
322 | * If configured, or requested by the commandline, devtmpfs will be | |
323 | * auto-mounted after the kernel mounted the root filesystem. | |
324 | */ | |
325 | int devtmpfs_mount(const char *mountpoint) | |
326 | { | |
327 | struct path path; | |
328 | int err; | |
329 | ||
330 | if (!dev_mount) | |
331 | return 0; | |
332 | ||
333 | if (!dev_mnt) | |
334 | return 0; | |
335 | ||
336 | err = kern_path(mountpoint, LOOKUP_FOLLOW, &path); | |
337 | if (err) | |
338 | return err; | |
339 | err = do_add_mount(dev_mnt, &path, 0, NULL); | |
340 | if (err) | |
341 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
342 | else | |
343 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
344 | path_put(&path); | |
345 | return err; | |
346 | } | |
347 | ||
348 | /* | |
349 | * Create devtmpfs instance, driver-core devices will add their device | |
350 | * nodes here. | |
351 | */ | |
352 | int __init devtmpfs_init(void) | |
353 | { | |
354 | int err; | |
355 | struct vfsmount *mnt; | |
356 | ||
357 | err = register_filesystem(&dev_fs_type); | |
358 | if (err) { | |
359 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
360 | "type %i\n", err); | |
361 | return err; | |
362 | } | |
363 | ||
364 | mnt = kern_mount(&dev_fs_type); | |
365 | if (IS_ERR(mnt)) { | |
366 | err = PTR_ERR(mnt); | |
367 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); | |
368 | unregister_filesystem(&dev_fs_type); | |
369 | return err; | |
370 | } | |
371 | dev_mnt = mnt; | |
372 | ||
373 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
374 | return 0; | |
375 | } |