blob: 855d4b1d619aec6244b182c3669b6efe2ec1f726 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 */
14
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <linux/syscalls.h>
16#include <linux/module.h>
17#include <linux/slab.h>
18#include <linux/list.h>
19#include <linux/mount.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080020#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#include <linux/dcache.h>
22#include <linux/mm.h>
Alexey Dobriyan4e950f62007-07-30 02:36:13 +040023#include <linux/err.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#include <linux/errno.h>
25#include <linux/dcookies.h>
Ingo Molnar353ab6e2006-03-26 01:37:12 -080026#include <linux/mutex.h>
Jan Blunck448678a2008-02-14 19:38:36 -080027#include <linux/path.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028#include <asm/uaccess.h>
29
30/* The dcookies are allocated from a kmem_cache and
31 * hashed onto a small number of lists. None of the
32 * code here is particularly performance critical
33 */
34struct dcookie_struct {
Jan Blunck448678a2008-02-14 19:38:36 -080035 struct path path;
Linus Torvalds1da177e2005-04-16 15:20:36 -070036 struct list_head hash_list;
37};
38
39static LIST_HEAD(dcookie_users);
Ingo Molnar353ab6e2006-03-26 01:37:12 -080040static DEFINE_MUTEX(dcookie_mutex);
Christoph Lametere18b8902006-12-06 20:33:20 -080041static struct kmem_cache *dcookie_cache __read_mostly;
Eric Dumazetfa3536c2006-03-26 01:37:24 -080042static struct list_head *dcookie_hashtable __read_mostly;
43static size_t hash_size __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45static inline int is_live(void)
46{
47 return !(list_empty(&dcookie_users));
48}
49
50
51/* The dentry is locked, its address will do for the cookie */
52static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
53{
Jan Blunck448678a2008-02-14 19:38:36 -080054 return (unsigned long)dcs->path.dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -070055}
56
57
58static size_t dcookie_hash(unsigned long dcookie)
59{
60 return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
61}
62
63
64static struct dcookie_struct * find_dcookie(unsigned long dcookie)
65{
66 struct dcookie_struct *found = NULL;
67 struct dcookie_struct * dcs;
68 struct list_head * pos;
69 struct list_head * list;
70
71 list = dcookie_hashtable + dcookie_hash(dcookie);
72
73 list_for_each(pos, list) {
74 dcs = list_entry(pos, struct dcookie_struct, hash_list);
75 if (dcookie_value(dcs) == dcookie) {
76 found = dcs;
77 break;
78 }
79 }
80
81 return found;
82}
83
84
85static void hash_dcookie(struct dcookie_struct * dcs)
86{
87 struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
88 list_add(&dcs->hash_list, list);
89}
90
91
Jan Blunck448678a2008-02-14 19:38:36 -080092static struct dcookie_struct *alloc_dcookie(struct path *path)
Linus Torvalds1da177e2005-04-16 15:20:36 -070093{
Jan Blunck448678a2008-02-14 19:38:36 -080094 struct dcookie_struct *dcs = kmem_cache_alloc(dcookie_cache,
95 GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 if (!dcs)
97 return NULL;
98
Jan Blunck448678a2008-02-14 19:38:36 -080099 path->dentry->d_cookie = dcs;
100 dcs->path = *path;
101 path_get(path);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 hash_dcookie(dcs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 return dcs;
104}
105
106
107/* This is the main kernel-side routine that retrieves the cookie
108 * value for a dentry/vfsmnt pair.
109 */
Jan Blunck448678a2008-02-14 19:38:36 -0800110int get_dcookie(struct path *path, unsigned long *cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111{
112 int err = 0;
113 struct dcookie_struct * dcs;
114
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800115 mutex_lock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
117 if (!is_live()) {
118 err = -EINVAL;
119 goto out;
120 }
121
Jan Blunck448678a2008-02-14 19:38:36 -0800122 dcs = path->dentry->d_cookie;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123
124 if (!dcs)
Jan Blunck448678a2008-02-14 19:38:36 -0800125 dcs = alloc_dcookie(path);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126
127 if (!dcs) {
128 err = -ENOMEM;
129 goto out;
130 }
131
132 *cookie = dcookie_value(dcs);
133
134out:
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800135 mutex_unlock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700136 return err;
137}
138
139
140/* And here is where the userspace process can look up the cookie value
141 * to retrieve the path.
142 */
143asmlinkage long sys_lookup_dcookie(u64 cookie64, char __user * buf, size_t len)
144{
145 unsigned long cookie = (unsigned long)cookie64;
146 int err = -EINVAL;
147 char * kbuf;
148 char * path;
149 size_t pathlen;
150 struct dcookie_struct * dcs;
151
152 /* we could leak path information to users
153 * without dir read permission without this
154 */
155 if (!capable(CAP_SYS_ADMIN))
156 return -EPERM;
157
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800158 mutex_lock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159
160 if (!is_live()) {
161 err = -EINVAL;
162 goto out;
163 }
164
165 if (!(dcs = find_dcookie(cookie)))
166 goto out;
167
168 err = -ENOMEM;
169 kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
170 if (!kbuf)
171 goto out;
172
173 /* FIXME: (deleted) ? */
Jan Blunckcf28b482008-02-14 19:38:44 -0800174 path = d_path(&dcs->path, kbuf, PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175
176 if (IS_ERR(path)) {
177 err = PTR_ERR(path);
178 goto out_free;
179 }
180
181 err = -ERANGE;
182
183 pathlen = kbuf + PAGE_SIZE - path;
184 if (pathlen <= len) {
185 err = pathlen;
186 if (copy_to_user(buf, path, pathlen))
187 err = -EFAULT;
188 }
189
190out_free:
191 kfree(kbuf);
192out:
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800193 mutex_unlock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 return err;
195}
196
197
198static int dcookie_init(void)
199{
200 struct list_head * d;
201 unsigned int i, hash_bits;
202 int err = -ENOMEM;
203
204 dcookie_cache = kmem_cache_create("dcookie_cache",
205 sizeof(struct dcookie_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900206 0, 0, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207
208 if (!dcookie_cache)
209 goto out;
210
211 dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
212 if (!dcookie_hashtable)
213 goto out_kmem;
214
215 err = 0;
216
217 /*
218 * Find the power-of-two list-heads that can fit into the allocation..
219 * We don't guarantee that "sizeof(struct list_head)" is necessarily
220 * a power-of-two.
221 */
222 hash_size = PAGE_SIZE / sizeof(struct list_head);
223 hash_bits = 0;
224 do {
225 hash_bits++;
226 } while ((hash_size >> hash_bits) != 0);
227 hash_bits--;
228
229 /*
230 * Re-calculate the actual number of entries and the mask
231 * from the number of bits we can fit.
232 */
233 hash_size = 1UL << hash_bits;
234
235 /* And initialize the newly allocated array */
236 d = dcookie_hashtable;
237 i = hash_size;
238 do {
239 INIT_LIST_HEAD(d);
240 d++;
241 i--;
242 } while (i);
243
244out:
245 return err;
246out_kmem:
247 kmem_cache_destroy(dcookie_cache);
248 goto out;
249}
250
251
252static void free_dcookie(struct dcookie_struct * dcs)
253{
Jan Blunck448678a2008-02-14 19:38:36 -0800254 dcs->path.dentry->d_cookie = NULL;
255 path_put(&dcs->path);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700256 kmem_cache_free(dcookie_cache, dcs);
257}
258
259
260static void dcookie_exit(void)
261{
262 struct list_head * list;
263 struct list_head * pos;
264 struct list_head * pos2;
265 struct dcookie_struct * dcs;
266 size_t i;
267
268 for (i = 0; i < hash_size; ++i) {
269 list = dcookie_hashtable + i;
270 list_for_each_safe(pos, pos2, list) {
271 dcs = list_entry(pos, struct dcookie_struct, hash_list);
272 list_del(&dcs->hash_list);
273 free_dcookie(dcs);
274 }
275 }
276
277 kfree(dcookie_hashtable);
278 kmem_cache_destroy(dcookie_cache);
279}
280
281
282struct dcookie_user {
283 struct list_head next;
284};
285
286struct dcookie_user * dcookie_register(void)
287{
288 struct dcookie_user * user;
289
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800290 mutex_lock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291
292 user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
293 if (!user)
294 goto out;
295
296 if (!is_live() && dcookie_init())
297 goto out_free;
298
299 list_add(&user->next, &dcookie_users);
300
301out:
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800302 mutex_unlock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 return user;
304out_free:
305 kfree(user);
306 user = NULL;
307 goto out;
308}
309
310
311void dcookie_unregister(struct dcookie_user * user)
312{
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800313 mutex_lock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314
315 list_del(&user->next);
316 kfree(user);
317
318 if (!is_live())
319 dcookie_exit();
320
Ingo Molnar353ab6e2006-03-26 01:37:12 -0800321 mutex_unlock(&dcookie_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322}
323
324EXPORT_SYMBOL_GPL(dcookie_register);
325EXPORT_SYMBOL_GPL(dcookie_unregister);
326EXPORT_SYMBOL_GPL(get_dcookie);