ia64/linux-2.6.18-xen.hg

view fs/dcookies.c @ 524:7f8b544237bf

netfront: Allow netfront in domain 0.

This is useful if your physical network device is in a utility domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue Apr 15 15:18:58 2008 +0100 (2008-04-15)
parents 831230e53067
children
line source
1 /*
2 * dcookies.c
3 *
4 * Copyright 2002 John Levon <levon@movementarian.org>
5 *
6 * Persistent cookie-path mappings. These are used by
7 * profilers to convert a per-task EIP value into something
8 * non-transitory that can be processed at a later date.
9 * This is done by locking the dentry/vfsmnt pair in the
10 * kernel until released by the tasks needing the persistent
11 * objects. The tag is simply an unsigned long that refers
12 * to the pair and can be looked up from userspace.
13 */
15 #include <linux/syscalls.h>
16 #include <linux/module.h>
17 #include <linux/slab.h>
18 #include <linux/list.h>
19 #include <linux/mount.h>
20 #include <linux/capability.h>
21 #include <linux/dcache.h>
22 #include <linux/mm.h>
23 #include <linux/errno.h>
24 #include <linux/dcookies.h>
25 #include <linux/mutex.h>
26 #include <asm/uaccess.h>
28 /* The dcookies are allocated from a kmem_cache and
29 * hashed onto a small number of lists. None of the
30 * code here is particularly performance critical
31 */
32 struct dcookie_struct {
33 struct dentry * dentry;
34 struct vfsmount * vfsmnt;
35 struct list_head hash_list;
36 };
38 static LIST_HEAD(dcookie_users);
39 static DEFINE_MUTEX(dcookie_mutex);
40 static kmem_cache_t *dcookie_cache __read_mostly;
41 static struct list_head *dcookie_hashtable __read_mostly;
42 static size_t hash_size __read_mostly;
44 static inline int is_live(void)
45 {
46 return !(list_empty(&dcookie_users));
47 }
50 /* The dentry is locked, its address will do for the cookie */
51 static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
52 {
53 return (unsigned long)dcs->dentry;
54 }
57 static size_t dcookie_hash(unsigned long dcookie)
58 {
59 return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
60 }
63 static struct dcookie_struct * find_dcookie(unsigned long dcookie)
64 {
65 struct dcookie_struct *found = NULL;
66 struct dcookie_struct * dcs;
67 struct list_head * pos;
68 struct list_head * list;
70 list = dcookie_hashtable + dcookie_hash(dcookie);
72 list_for_each(pos, list) {
73 dcs = list_entry(pos, struct dcookie_struct, hash_list);
74 if (dcookie_value(dcs) == dcookie) {
75 found = dcs;
76 break;
77 }
78 }
80 return found;
81 }
84 static void hash_dcookie(struct dcookie_struct * dcs)
85 {
86 struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
87 list_add(&dcs->hash_list, list);
88 }
91 static struct dcookie_struct * alloc_dcookie(struct dentry * dentry,
92 struct vfsmount * vfsmnt)
93 {
94 struct dcookie_struct * dcs = kmem_cache_alloc(dcookie_cache, GFP_KERNEL);
95 if (!dcs)
96 return NULL;
98 dentry->d_cookie = dcs;
100 dcs->dentry = dget(dentry);
101 dcs->vfsmnt = mntget(vfsmnt);
102 hash_dcookie(dcs);
104 return dcs;
105 }
108 /* This is the main kernel-side routine that retrieves the cookie
109 * value for a dentry/vfsmnt pair.
110 */
111 int get_dcookie(struct dentry * dentry, struct vfsmount * vfsmnt,
112 unsigned long * cookie)
113 {
114 int err = 0;
115 struct dcookie_struct * dcs;
117 mutex_lock(&dcookie_mutex);
119 if (!is_live()) {
120 err = -EINVAL;
121 goto out;
122 }
124 dcs = dentry->d_cookie;
126 if (!dcs)
127 dcs = alloc_dcookie(dentry, vfsmnt);
129 if (!dcs) {
130 err = -ENOMEM;
131 goto out;
132 }
134 *cookie = dcookie_value(dcs);
136 out:
137 mutex_unlock(&dcookie_mutex);
138 return err;
139 }
142 /* And here is where the userspace process can look up the cookie value
143 * to retrieve the path.
144 */
145 asmlinkage long sys_lookup_dcookie(u64 cookie64, char __user * buf, size_t len)
146 {
147 unsigned long cookie = (unsigned long)cookie64;
148 int err = -EINVAL;
149 char * kbuf;
150 char * path;
151 size_t pathlen;
152 struct dcookie_struct * dcs;
154 /* we could leak path information to users
155 * without dir read permission without this
156 */
157 if (!capable(CAP_SYS_ADMIN))
158 return -EPERM;
160 mutex_lock(&dcookie_mutex);
162 if (!is_live()) {
163 err = -EINVAL;
164 goto out;
165 }
167 if (!(dcs = find_dcookie(cookie)))
168 goto out;
170 err = -ENOMEM;
171 kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
172 if (!kbuf)
173 goto out;
175 /* FIXME: (deleted) ? */
176 path = d_path(dcs->dentry, dcs->vfsmnt, kbuf, PAGE_SIZE);
178 if (IS_ERR(path)) {
179 err = PTR_ERR(path);
180 goto out_free;
181 }
183 err = -ERANGE;
185 pathlen = kbuf + PAGE_SIZE - path;
186 if (pathlen <= len) {
187 err = pathlen;
188 if (copy_to_user(buf, path, pathlen))
189 err = -EFAULT;
190 }
192 out_free:
193 kfree(kbuf);
194 out:
195 mutex_unlock(&dcookie_mutex);
196 return err;
197 }
200 static int dcookie_init(void)
201 {
202 struct list_head * d;
203 unsigned int i, hash_bits;
204 int err = -ENOMEM;
206 dcookie_cache = kmem_cache_create("dcookie_cache",
207 sizeof(struct dcookie_struct),
208 0, 0, NULL, NULL);
210 if (!dcookie_cache)
211 goto out;
213 dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
214 if (!dcookie_hashtable)
215 goto out_kmem;
217 err = 0;
219 /*
220 * Find the power-of-two list-heads that can fit into the allocation..
221 * We don't guarantee that "sizeof(struct list_head)" is necessarily
222 * a power-of-two.
223 */
224 hash_size = PAGE_SIZE / sizeof(struct list_head);
225 hash_bits = 0;
226 do {
227 hash_bits++;
228 } while ((hash_size >> hash_bits) != 0);
229 hash_bits--;
231 /*
232 * Re-calculate the actual number of entries and the mask
233 * from the number of bits we can fit.
234 */
235 hash_size = 1UL << hash_bits;
237 /* And initialize the newly allocated array */
238 d = dcookie_hashtable;
239 i = hash_size;
240 do {
241 INIT_LIST_HEAD(d);
242 d++;
243 i--;
244 } while (i);
246 out:
247 return err;
248 out_kmem:
249 kmem_cache_destroy(dcookie_cache);
250 goto out;
251 }
254 static void free_dcookie(struct dcookie_struct * dcs)
255 {
256 dcs->dentry->d_cookie = NULL;
257 dput(dcs->dentry);
258 mntput(dcs->vfsmnt);
259 kmem_cache_free(dcookie_cache, dcs);
260 }
263 static void dcookie_exit(void)
264 {
265 struct list_head * list;
266 struct list_head * pos;
267 struct list_head * pos2;
268 struct dcookie_struct * dcs;
269 size_t i;
271 for (i = 0; i < hash_size; ++i) {
272 list = dcookie_hashtable + i;
273 list_for_each_safe(pos, pos2, list) {
274 dcs = list_entry(pos, struct dcookie_struct, hash_list);
275 list_del(&dcs->hash_list);
276 free_dcookie(dcs);
277 }
278 }
280 kfree(dcookie_hashtable);
281 kmem_cache_destroy(dcookie_cache);
282 }
285 struct dcookie_user {
286 struct list_head next;
287 };
289 struct dcookie_user * dcookie_register(void)
290 {
291 struct dcookie_user * user;
293 mutex_lock(&dcookie_mutex);
295 user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
296 if (!user)
297 goto out;
299 if (!is_live() && dcookie_init())
300 goto out_free;
302 list_add(&user->next, &dcookie_users);
304 out:
305 mutex_unlock(&dcookie_mutex);
306 return user;
307 out_free:
308 kfree(user);
309 user = NULL;
310 goto out;
311 }
314 void dcookie_unregister(struct dcookie_user * user)
315 {
316 mutex_lock(&dcookie_mutex);
318 list_del(&user->next);
319 kfree(user);
321 if (!is_live())
322 dcookie_exit();
324 mutex_unlock(&dcookie_mutex);
325 }
327 EXPORT_SYMBOL_GPL(dcookie_register);
328 EXPORT_SYMBOL_GPL(dcookie_unregister);
329 EXPORT_SYMBOL_GPL(get_dcookie);