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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 | |
9 | * filesystem. The node is named after the the name of the device, | |
10 | * or the susbsytem can provide a custom name. All devices are | |
11 | * owned by root and have a mode of 0600. | |
12 | */ | |
13 | ||
14 | #include <linux/kernel.h> | |
15 | #include <linux/syscalls.h> | |
16 | #include <linux/mount.h> | |
17 | #include <linux/device.h> | |
18 | #include <linux/genhd.h> | |
19 | #include <linux/namei.h> | |
20 | #include <linux/fs.h> | |
21 | #include <linux/shmem_fs.h> | |
22 | #include <linux/cred.h> | |
23 | #include <linux/init_task.h> | |
24 | ||
25 | static struct vfsmount *dev_mnt; | |
26 | ||
27 | #if defined CONFIG_DEVTMPFS_MOUNT | |
28 | static int dev_mount = 1; | |
29 | #else | |
30 | static int dev_mount; | |
31 | #endif | |
32 | ||
33 | static int __init mount_param(char *str) | |
34 | { | |
35 | dev_mount = simple_strtoul(str, NULL, 0); | |
36 | return 1; | |
37 | } | |
38 | __setup("devtmpfs.mount=", mount_param); | |
39 | ||
40 | static int dev_get_sb(struct file_system_type *fs_type, int flags, | |
41 | const char *dev_name, void *data, struct vfsmount *mnt) | |
42 | { | |
43 | return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt); | |
44 | } | |
45 | ||
46 | static struct file_system_type dev_fs_type = { | |
47 | .name = "devtmpfs", | |
48 | .get_sb = dev_get_sb, | |
49 | .kill_sb = kill_litter_super, | |
50 | }; | |
51 | ||
52 | #ifdef CONFIG_BLOCK | |
53 | static inline int is_blockdev(struct device *dev) | |
54 | { | |
55 | return dev->class == &block_class; | |
56 | } | |
57 | #else | |
58 | static inline int is_blockdev(struct device *dev) { return 0; } | |
59 | #endif | |
60 | ||
61 | static int dev_mkdir(const char *name, mode_t mode) | |
62 | { | |
63 | struct nameidata nd; | |
64 | struct dentry *dentry; | |
65 | int err; | |
66 | ||
67 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
68 | name, LOOKUP_PARENT, &nd); | |
69 | if (err) | |
70 | return err; | |
71 | ||
72 | dentry = lookup_create(&nd, 1); | |
73 | if (!IS_ERR(dentry)) { | |
74 | err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode); | |
75 | dput(dentry); | |
76 | } else { | |
77 | err = PTR_ERR(dentry); | |
78 | } | |
79 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
80 | ||
81 | path_put(&nd.path); | |
82 | return err; | |
83 | } | |
84 | ||
85 | static int create_path(const char *nodepath) | |
86 | { | |
87 | char *path; | |
88 | struct nameidata nd; | |
89 | int err = 0; | |
90 | ||
91 | path = kstrdup(nodepath, GFP_KERNEL); | |
92 | if (!path) | |
93 | return -ENOMEM; | |
94 | ||
95 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
96 | path, LOOKUP_PARENT, &nd); | |
97 | if (err == 0) { | |
98 | struct dentry *dentry; | |
99 | ||
100 | /* create directory right away */ | |
101 | dentry = lookup_create(&nd, 1); | |
102 | if (!IS_ERR(dentry)) { | |
103 | err = vfs_mkdir(nd.path.dentry->d_inode, | |
104 | dentry, 0755); | |
105 | dput(dentry); | |
106 | } | |
107 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
108 | ||
109 | path_put(&nd.path); | |
110 | } else if (err == -ENOENT) { | |
111 | char *s; | |
112 | ||
113 | /* parent directories do not exist, create them */ | |
114 | s = path; | |
115 | while (1) { | |
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 | } | |
126 | } | |
127 | ||
128 | kfree(path); | |
129 | return err; | |
130 | } | |
131 | ||
132 | int devtmpfs_create_node(struct device *dev) | |
133 | { | |
134 | const char *tmp = NULL; | |
135 | const char *nodename; | |
136 | const struct cred *curr_cred; | |
137 | mode_t mode; | |
138 | struct nameidata nd; | |
139 | struct dentry *dentry; | |
140 | int err; | |
141 | ||
142 | if (!dev_mnt) | |
143 | return 0; | |
144 | ||
145 | nodename = device_get_nodename(dev, &tmp); | |
146 | if (!nodename) | |
147 | return -ENOMEM; | |
148 | ||
149 | if (is_blockdev(dev)) | |
150 | mode = S_IFBLK|0600; | |
151 | else | |
152 | mode = S_IFCHR|0600; | |
153 | ||
154 | curr_cred = override_creds(&init_cred); | |
155 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
156 | nodename, LOOKUP_PARENT, &nd); | |
157 | if (err == -ENOENT) { | |
158 | /* create missing parent directories */ | |
159 | create_path(nodename); | |
160 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
161 | nodename, LOOKUP_PARENT, &nd); | |
162 | if (err) | |
163 | goto out; | |
164 | } | |
165 | ||
166 | dentry = lookup_create(&nd, 0); | |
167 | if (!IS_ERR(dentry)) { | |
168 | err = vfs_mknod(nd.path.dentry->d_inode, | |
169 | dentry, mode, dev->devt); | |
170 | /* mark as kernel created inode */ | |
171 | if (!err) | |
172 | dentry->d_inode->i_private = &dev_mnt; | |
173 | dput(dentry); | |
174 | } else { | |
175 | err = PTR_ERR(dentry); | |
176 | } | |
177 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
178 | ||
179 | path_put(&nd.path); | |
180 | out: | |
181 | kfree(tmp); | |
182 | revert_creds(curr_cred); | |
183 | return err; | |
184 | } | |
185 | ||
186 | static int dev_rmdir(const char *name) | |
187 | { | |
188 | struct nameidata nd; | |
189 | struct dentry *dentry; | |
190 | int err; | |
191 | ||
192 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
193 | name, LOOKUP_PARENT, &nd); | |
194 | if (err) | |
195 | return err; | |
196 | ||
197 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
198 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
199 | if (!IS_ERR(dentry)) { | |
200 | if (dentry->d_inode) | |
201 | err = vfs_rmdir(nd.path.dentry->d_inode, dentry); | |
202 | else | |
203 | err = -ENOENT; | |
204 | dput(dentry); | |
205 | } else { | |
206 | err = PTR_ERR(dentry); | |
207 | } | |
208 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
209 | ||
210 | path_put(&nd.path); | |
211 | return err; | |
212 | } | |
213 | ||
214 | static int delete_path(const char *nodepath) | |
215 | { | |
216 | const char *path; | |
217 | int err = 0; | |
218 | ||
219 | path = kstrdup(nodepath, GFP_KERNEL); | |
220 | if (!path) | |
221 | return -ENOMEM; | |
222 | ||
223 | while (1) { | |
224 | char *base; | |
225 | ||
226 | base = strrchr(path, '/'); | |
227 | if (!base) | |
228 | break; | |
229 | base[0] = '\0'; | |
230 | err = dev_rmdir(path); | |
231 | if (err) | |
232 | break; | |
233 | } | |
234 | ||
235 | kfree(path); | |
236 | return err; | |
237 | } | |
238 | ||
239 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
240 | { | |
241 | /* did we create it */ | |
242 | if (inode->i_private != &dev_mnt) | |
243 | return 0; | |
244 | ||
245 | /* does the dev_t match */ | |
246 | if (is_blockdev(dev)) { | |
247 | if (!S_ISBLK(stat->mode)) | |
248 | return 0; | |
249 | } else { | |
250 | if (!S_ISCHR(stat->mode)) | |
251 | return 0; | |
252 | } | |
253 | if (stat->rdev != dev->devt) | |
254 | return 0; | |
255 | ||
256 | /* ours */ | |
257 | return 1; | |
258 | } | |
259 | ||
260 | int devtmpfs_delete_node(struct device *dev) | |
261 | { | |
262 | const char *tmp = NULL; | |
263 | const char *nodename; | |
264 | const struct cred *curr_cred; | |
265 | struct nameidata nd; | |
266 | struct dentry *dentry; | |
267 | struct kstat stat; | |
268 | int deleted = 1; | |
269 | int err; | |
270 | ||
271 | if (!dev_mnt) | |
272 | return 0; | |
273 | ||
274 | nodename = device_get_nodename(dev, &tmp); | |
275 | if (!nodename) | |
276 | return -ENOMEM; | |
277 | ||
278 | curr_cred = override_creds(&init_cred); | |
279 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
280 | nodename, LOOKUP_PARENT, &nd); | |
281 | if (err) | |
282 | goto out; | |
283 | ||
284 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
285 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
286 | if (!IS_ERR(dentry)) { | |
287 | if (dentry->d_inode) { | |
288 | err = vfs_getattr(nd.path.mnt, dentry, &stat); | |
289 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { | |
290 | err = vfs_unlink(nd.path.dentry->d_inode, | |
291 | dentry); | |
292 | if (!err || err == -ENOENT) | |
293 | deleted = 1; | |
294 | } | |
295 | } else { | |
296 | err = -ENOENT; | |
297 | } | |
298 | dput(dentry); | |
299 | } else { | |
300 | err = PTR_ERR(dentry); | |
301 | } | |
302 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
303 | ||
304 | path_put(&nd.path); | |
305 | if (deleted && strchr(nodename, '/')) | |
306 | delete_path(nodename); | |
307 | out: | |
308 | kfree(tmp); | |
309 | revert_creds(curr_cred); | |
310 | return err; | |
311 | } | |
312 | ||
313 | /* | |
314 | * If configured, or requested by the commandline, devtmpfs will be | |
315 | * auto-mounted after the kernel mounted the root filesystem. | |
316 | */ | |
317 | int devtmpfs_mount(const char *mountpoint) | |
318 | { | |
319 | struct path path; | |
320 | int err; | |
321 | ||
322 | if (!dev_mount) | |
323 | return 0; | |
324 | ||
325 | if (!dev_mnt) | |
326 | return 0; | |
327 | ||
328 | err = kern_path(mountpoint, LOOKUP_FOLLOW, &path); | |
329 | if (err) | |
330 | return err; | |
331 | err = do_add_mount(dev_mnt, &path, 0, NULL); | |
332 | if (err) | |
333 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
334 | else | |
335 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
336 | path_put(&path); | |
337 | return err; | |
338 | } | |
339 | ||
340 | /* | |
341 | * Create devtmpfs instance, driver-core devices will add their device | |
342 | * nodes here. | |
343 | */ | |
344 | int __init devtmpfs_init(void) | |
345 | { | |
346 | int err; | |
347 | struct vfsmount *mnt; | |
348 | ||
349 | err = register_filesystem(&dev_fs_type); | |
350 | if (err) { | |
351 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
352 | "type %i\n", err); | |
353 | return err; | |
354 | } | |
355 | ||
356 | mnt = kern_mount(&dev_fs_type); | |
357 | if (IS_ERR(mnt)) { | |
358 | err = PTR_ERR(mnt); | |
359 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); | |
360 | unregister_filesystem(&dev_fs_type); | |
361 | return err; | |
362 | } | |
363 | dev_mnt = mnt; | |
364 | ||
365 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
366 | return 0; | |
367 | } |