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