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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 KS |
103 | path = kstrdup(nodepath, GFP_KERNEL); |
104 | if (!path) | |
105 | return -ENOMEM; | |
2b2af54a | 106 | s = path; |
ed413ae6 | 107 | for (;;) { |
2b2af54a KS |
108 | s = strchr(s, '/'); |
109 | if (!s) | |
110 | break; | |
111 | s[0] = '\0'; | |
112 | err = dev_mkdir(path, 0755); | |
113 | if (err && err != -EEXIST) | |
114 | break; | |
115 | s[0] = '/'; | |
116 | s++; | |
117 | } | |
ed413ae6 | 118 | kfree(path); |
2b2af54a | 119 | } |
f1f76f86 | 120 | mutex_unlock(&dirlock); |
2b2af54a KS |
121 | return err; |
122 | } | |
123 | ||
124 | int devtmpfs_create_node(struct device *dev) | |
125 | { | |
126 | const char *tmp = NULL; | |
127 | const char *nodename; | |
128 | const struct cred *curr_cred; | |
e454cea2 | 129 | mode_t mode = 0; |
2b2af54a KS |
130 | struct nameidata nd; |
131 | struct dentry *dentry; | |
132 | int err; | |
133 | ||
134 | if (!dev_mnt) | |
135 | return 0; | |
136 | ||
e454cea2 | 137 | nodename = device_get_devnode(dev, &mode, &tmp); |
2b2af54a KS |
138 | if (!nodename) |
139 | return -ENOMEM; | |
140 | ||
e454cea2 KS |
141 | if (mode == 0) |
142 | mode = 0600; | |
2b2af54a | 143 | if (is_blockdev(dev)) |
e454cea2 | 144 | mode |= S_IFBLK; |
2b2af54a | 145 | else |
e454cea2 | 146 | mode |= S_IFCHR; |
2b2af54a KS |
147 | |
148 | curr_cred = override_creds(&init_cred); | |
00926996 | 149 | |
2b2af54a KS |
150 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, |
151 | nodename, LOOKUP_PARENT, &nd); | |
152 | if (err == -ENOENT) { | |
2b2af54a KS |
153 | create_path(nodename); |
154 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
155 | nodename, LOOKUP_PARENT, &nd); | |
2b2af54a | 156 | } |
00926996 KS |
157 | if (err) |
158 | goto out; | |
2b2af54a KS |
159 | |
160 | dentry = lookup_create(&nd, 0); | |
161 | if (!IS_ERR(dentry)) { | |
162 | err = vfs_mknod(nd.path.dentry->d_inode, | |
163 | dentry, mode, dev->devt); | |
00926996 KS |
164 | if (!err) { |
165 | struct iattr newattrs; | |
166 | ||
167 | /* fixup possibly umasked mode */ | |
168 | newattrs.ia_mode = mode; | |
169 | newattrs.ia_valid = ATTR_MODE; | |
170 | mutex_lock(&dentry->d_inode->i_mutex); | |
171 | notify_change(dentry, &newattrs); | |
172 | mutex_unlock(&dentry->d_inode->i_mutex); | |
173 | ||
174 | /* mark as kernel-created inode */ | |
2b2af54a | 175 | dentry->d_inode->i_private = &dev_mnt; |
00926996 | 176 | } |
2b2af54a KS |
177 | dput(dentry); |
178 | } else { | |
179 | err = PTR_ERR(dentry); | |
180 | } | |
2b2af54a | 181 | |
00926996 | 182 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
183 | path_put(&nd.path); |
184 | out: | |
185 | kfree(tmp); | |
186 | revert_creds(curr_cred); | |
187 | return err; | |
188 | } | |
189 | ||
190 | static int dev_rmdir(const char *name) | |
191 | { | |
192 | struct nameidata nd; | |
193 | struct dentry *dentry; | |
194 | int err; | |
195 | ||
196 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
197 | name, LOOKUP_PARENT, &nd); | |
198 | if (err) | |
199 | return err; | |
200 | ||
201 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
202 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
203 | if (!IS_ERR(dentry)) { | |
015bf43b KS |
204 | if (dentry->d_inode) { |
205 | if (dentry->d_inode->i_private == &dev_mnt) | |
206 | err = vfs_rmdir(nd.path.dentry->d_inode, | |
207 | dentry); | |
208 | else | |
209 | err = -EPERM; | |
210 | } else { | |
2b2af54a | 211 | err = -ENOENT; |
015bf43b | 212 | } |
2b2af54a KS |
213 | dput(dentry); |
214 | } else { | |
215 | err = PTR_ERR(dentry); | |
216 | } | |
2b2af54a | 217 | |
015bf43b | 218 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2b2af54a KS |
219 | path_put(&nd.path); |
220 | return err; | |
221 | } | |
222 | ||
223 | static int delete_path(const char *nodepath) | |
224 | { | |
225 | const char *path; | |
226 | int err = 0; | |
227 | ||
228 | path = kstrdup(nodepath, GFP_KERNEL); | |
229 | if (!path) | |
230 | return -ENOMEM; | |
231 | ||
f1f76f86 | 232 | mutex_lock(&dirlock); |
ed413ae6 | 233 | for (;;) { |
2b2af54a KS |
234 | char *base; |
235 | ||
236 | base = strrchr(path, '/'); | |
237 | if (!base) | |
238 | break; | |
239 | base[0] = '\0'; | |
240 | err = dev_rmdir(path); | |
241 | if (err) | |
242 | break; | |
243 | } | |
f1f76f86 | 244 | mutex_unlock(&dirlock); |
2b2af54a KS |
245 | |
246 | kfree(path); | |
247 | return err; | |
248 | } | |
249 | ||
250 | static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) | |
251 | { | |
252 | /* did we create it */ | |
253 | if (inode->i_private != &dev_mnt) | |
254 | return 0; | |
255 | ||
256 | /* does the dev_t match */ | |
257 | if (is_blockdev(dev)) { | |
258 | if (!S_ISBLK(stat->mode)) | |
259 | return 0; | |
260 | } else { | |
261 | if (!S_ISCHR(stat->mode)) | |
262 | return 0; | |
263 | } | |
264 | if (stat->rdev != dev->devt) | |
265 | return 0; | |
266 | ||
267 | /* ours */ | |
268 | return 1; | |
269 | } | |
270 | ||
271 | int devtmpfs_delete_node(struct device *dev) | |
272 | { | |
273 | const char *tmp = NULL; | |
274 | const char *nodename; | |
275 | const struct cred *curr_cred; | |
276 | struct nameidata nd; | |
277 | struct dentry *dentry; | |
278 | struct kstat stat; | |
279 | int deleted = 1; | |
280 | int err; | |
281 | ||
282 | if (!dev_mnt) | |
283 | return 0; | |
284 | ||
e454cea2 | 285 | nodename = device_get_devnode(dev, NULL, &tmp); |
2b2af54a KS |
286 | if (!nodename) |
287 | return -ENOMEM; | |
288 | ||
289 | curr_cred = override_creds(&init_cred); | |
290 | err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt, | |
291 | nodename, LOOKUP_PARENT, &nd); | |
292 | if (err) | |
293 | goto out; | |
294 | ||
295 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
296 | dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len); | |
297 | if (!IS_ERR(dentry)) { | |
298 | if (dentry->d_inode) { | |
299 | err = vfs_getattr(nd.path.mnt, dentry, &stat); | |
300 | if (!err && dev_mynode(dev, dentry->d_inode, &stat)) { | |
301 | err = vfs_unlink(nd.path.dentry->d_inode, | |
302 | dentry); | |
303 | if (!err || err == -ENOENT) | |
304 | deleted = 1; | |
305 | } | |
306 | } else { | |
307 | err = -ENOENT; | |
308 | } | |
309 | dput(dentry); | |
310 | } else { | |
311 | err = PTR_ERR(dentry); | |
312 | } | |
313 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
314 | ||
315 | path_put(&nd.path); | |
316 | if (deleted && strchr(nodename, '/')) | |
317 | delete_path(nodename); | |
318 | out: | |
319 | kfree(tmp); | |
320 | revert_creds(curr_cred); | |
321 | return err; | |
322 | } | |
323 | ||
324 | /* | |
325 | * If configured, or requested by the commandline, devtmpfs will be | |
326 | * auto-mounted after the kernel mounted the root filesystem. | |
327 | */ | |
073120cc | 328 | int devtmpfs_mount(const char *mntdir) |
2b2af54a | 329 | { |
2b2af54a KS |
330 | int err; |
331 | ||
332 | if (!dev_mount) | |
333 | return 0; | |
334 | ||
335 | if (!dev_mnt) | |
336 | return 0; | |
337 | ||
073120cc | 338 | err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL); |
2b2af54a KS |
339 | if (err) |
340 | printk(KERN_INFO "devtmpfs: error mounting %i\n", err); | |
341 | else | |
342 | printk(KERN_INFO "devtmpfs: mounted\n"); | |
2b2af54a KS |
343 | return err; |
344 | } | |
345 | ||
346 | /* | |
347 | * Create devtmpfs instance, driver-core devices will add their device | |
348 | * nodes here. | |
349 | */ | |
350 | int __init devtmpfs_init(void) | |
351 | { | |
352 | int err; | |
353 | struct vfsmount *mnt; | |
354 | ||
355 | err = register_filesystem(&dev_fs_type); | |
356 | if (err) { | |
357 | printk(KERN_ERR "devtmpfs: unable to register devtmpfs " | |
358 | "type %i\n", err); | |
359 | return err; | |
360 | } | |
361 | ||
03d673e6 | 362 | mnt = kern_mount_data(&dev_fs_type, "mode=0755"); |
2b2af54a KS |
363 | if (IS_ERR(mnt)) { |
364 | err = PTR_ERR(mnt); | |
365 | printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); | |
366 | unregister_filesystem(&dev_fs_type); | |
367 | return err; | |
368 | } | |
369 | dev_mnt = mnt; | |
370 | ||
371 | printk(KERN_INFO "devtmpfs: initialized\n"); | |
372 | return 0; | |
373 | } |