[linux-2.6-block.git] / fs / dcookies.c

/*
 * dcookies.c
 *
 * Copyright 2002 John Levon <levon@movementarian.org>
 *
 * Persistent cookie-path mappings. These are used by
 * profilers to convert a per-task EIP value into something
 * non-transitory that can be processed at a later date.
 * This is done by locking the dentry/vfsmnt pair in the
 * kernel until released by the tasks needing the persistent
 * objects. The tag is simply an unsigned long that refers
 * to the pair and can be looked up from userspace.
 */

#include <linux/config.h>
#include <linux/syscalls.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/mount.h>
#include <linux/capability.h>
#include <linux/dcache.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/dcookies.h>
#include <asm/uaccess.h>

/* The dcookies are allocated from a kmem_cache and
 * hashed onto a small number of lists. None of the
 * code here is particularly performance critical
 */
struct dcookie_struct {
	struct dentry * dentry;
	struct vfsmount * vfsmnt;
	struct list_head hash_list;
};

static LIST_HEAD(dcookie_users);
static DECLARE_MUTEX(dcookie_sem);
static kmem_cache_t * dcookie_cache;
static struct list_head * dcookie_hashtable;
static size_t hash_size;

static inline int is_live(void)
{
	return !(list_empty(&dcookie_users));
}


/* The dentry is locked, its address will do for the cookie */
static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
{
	return (unsigned long)dcs->dentry;
}


static size_t dcookie_hash(unsigned long dcookie)
{
	return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
}


static struct dcookie_struct * find_dcookie(unsigned long dcookie)
{
	struct dcookie_struct *found = NULL;
	struct dcookie_struct * dcs;
	struct list_head * pos;
	struct list_head * list;

	list = dcookie_hashtable + dcookie_hash(dcookie);

	list_for_each(pos, list) {
		dcs = list_entry(pos, struct dcookie_struct, hash_list);
		if (dcookie_value(dcs) == dcookie) {
			found = dcs;
			break;
		}
	}

	return found;
}


static void hash_dcookie(struct dcookie_struct * dcs)
{
	struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
	list_add(&dcs->hash_list, list);
}


static struct dcookie_struct * alloc_dcookie(struct dentry * dentry,
	struct vfsmount * vfsmnt)
{
	struct dcookie_struct * dcs = kmem_cache_alloc(dcookie_cache, GFP_KERNEL);
	if (!dcs)
		return NULL;

	dentry->d_cookie = dcs;

	dcs->dentry = dget(dentry);
	dcs->vfsmnt = mntget(vfsmnt);
	hash_dcookie(dcs);

	return dcs;
}


/* This is the main kernel-side routine that retrieves the cookie
 * value for a dentry/vfsmnt pair.
 */
int get_dcookie(struct dentry * dentry, struct vfsmount * vfsmnt,
	unsigned long * cookie)
{
	int err = 0;
	struct dcookie_struct * dcs;

	down(&dcookie_sem);

	if (!is_live()) {
		err = -EINVAL;
		goto out;
	}

	dcs = dentry->d_cookie;

	if (!dcs)
		dcs = alloc_dcookie(dentry, vfsmnt);

	if (!dcs) {
		err = -ENOMEM;
		goto out;
	}

	*cookie = dcookie_value(dcs);

out:
	up(&dcookie_sem);
	return err;
}


/* And here is where the userspace process can look up the cookie value
 * to retrieve the path.
 */
asmlinkage long sys_lookup_dcookie(u64 cookie64, char __user * buf, size_t len)
{
	unsigned long cookie = (unsigned long)cookie64;
	int err = -EINVAL;
	char * kbuf;
	char * path;
	size_t pathlen;
	struct dcookie_struct * dcs;

	/* we could leak path information to users
	 * without dir read permission without this
	 */
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	down(&dcookie_sem);

	if (!is_live()) {
		err = -EINVAL;
		goto out;
	}

	if (!(dcs = find_dcookie(cookie)))
		goto out;

	err = -ENOMEM;
	kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!kbuf)
		goto out;

	/* FIXME: (deleted) ? */
	path = d_path(dcs->dentry, dcs->vfsmnt, kbuf, PAGE_SIZE);

	if (IS_ERR(path)) {
		err = PTR_ERR(path);
		goto out_free;
	}

	err = -ERANGE;
 
	pathlen = kbuf + PAGE_SIZE - path;
	if (pathlen <= len) {
		err = pathlen;
		if (copy_to_user(buf, path, pathlen))
			err = -EFAULT;
	}

out_free:
	kfree(kbuf);
out:
	up(&dcookie_sem);
	return err;
}


static int dcookie_init(void)
{
	struct list_head * d;
	unsigned int i, hash_bits;
	int err = -ENOMEM;

	dcookie_cache = kmem_cache_create("dcookie_cache",
		sizeof(struct dcookie_struct),
		0, 0, NULL, NULL);

	if (!dcookie_cache)
		goto out;

	dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!dcookie_hashtable)
		goto out_kmem;

	err = 0;

	/*
	 * Find the power-of-two list-heads that can fit into the allocation..
	 * We don't guarantee that "sizeof(struct list_head)" is necessarily
	 * a power-of-two.
	 */
	hash_size = PAGE_SIZE / sizeof(struct list_head);
	hash_bits = 0;
	do {
		hash_bits++;
	} while ((hash_size >> hash_bits) != 0);
	hash_bits--;

	/*
	 * Re-calculate the actual number of entries and the mask
	 * from the number of bits we can fit.
	 */
	hash_size = 1UL << hash_bits;

	/* And initialize the newly allocated array */
	d = dcookie_hashtable;
	i = hash_size;
	do {
		INIT_LIST_HEAD(d);
		d++;
		i--;
	} while (i);

out:
	return err;
out_kmem:
	kmem_cache_destroy(dcookie_cache);
	goto out;
}


static void free_dcookie(struct dcookie_struct * dcs)
{
	dcs->dentry->d_cookie = NULL;
	dput(dcs->dentry);
	mntput(dcs->vfsmnt);
	kmem_cache_free(dcookie_cache, dcs);
}


static void dcookie_exit(void)
{
	struct list_head * list;
	struct list_head * pos;
	struct list_head * pos2;
	struct dcookie_struct * dcs;
	size_t i;

	for (i = 0; i < hash_size; ++i) {
		list = dcookie_hashtable + i;
		list_for_each_safe(pos, pos2, list) {
			dcs = list_entry(pos, struct dcookie_struct, hash_list);
			list_del(&dcs->hash_list);
			free_dcookie(dcs);
		}
	}

	kfree(dcookie_hashtable);
	kmem_cache_destroy(dcookie_cache);
}


struct dcookie_user {
	struct list_head next;
};
 
struct dcookie_user * dcookie_register(void)
{
	struct dcookie_user * user;

	down(&dcookie_sem);

	user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
	if (!user)
		goto out;

	if (!is_live() && dcookie_init())
		goto out_free;

	list_add(&user->next, &dcookie_users);

out:
	up(&dcookie_sem);
	return user;
out_free:
	kfree(user);
	user = NULL;
	goto out;
}


void dcookie_unregister(struct dcookie_user * user)
{
	down(&dcookie_sem);

	list_del(&user->next);
	kfree(user);

	if (!is_live())
		dcookie_exit();

	up(&dcookie_sem);
}

EXPORT_SYMBOL_GPL(dcookie_register);
EXPORT_SYMBOL_GPL(dcookie_unregister);
EXPORT_SYMBOL_GPL(get_dcookie);
Commit	Line	Data
1da177e4 LT	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	*/
	14
	15	#include <linux/config.h>
	16	#include <linux/syscalls.h>
	17	#include <linux/module.h>
	18	#include <linux/slab.h>
	19	#include <linux/list.h>
	20	#include <linux/mount.h>
16f7e0fe	21	#include <linux/capability.h>
1da177e4 LT	22	#include <linux/dcache.h>
	23	#include <linux/mm.h>
	24	#include <linux/errno.h>
	25	#include <linux/dcookies.h>
	26	#include <asm/uaccess.h>
	27
	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	};
	37
	38	static LIST_HEAD(dcookie_users);
	39	static DECLARE_MUTEX(dcookie_sem);
	40	static kmem_cache_t * dcookie_cache;
	41	static struct list_head * dcookie_hashtable;
	42	static size_t hash_size;
	43
	44	static inline int is_live(void)
	45	{
	46	return !(list_empty(&dcookie_users));
	47	}
	48
	49
	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	}
	55
	56
	57	static size_t dcookie_hash(unsigned long dcookie)
	58	{
	59	return (dcookie >> L1_CACHE_SHIFT) & (hash_size - 1);
	60	}
	61
	62
	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;
	69
	70	list = dcookie_hashtable + dcookie_hash(dcookie);
	71
	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	}
	79
	80	return found;
	81	}
	82
	83
	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	}
89
90
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;
97
1da177e4 LT	98	dentry->d_cookie = dcs;
1da177e4 LT	99
732dbef6 MS	100	dcs->dentry = dget(dentry);
732dbef6 MS	101	dcs->vfsmnt = mntget(vfsmnt);
1da177e4 LT	102	hash_dcookie(dcs);
	103
	104	return dcs;
	105	}
	106
	107
	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;
	116
	117	down(&dcookie_sem);
	118
	119	if (!is_live()) {
	120	err = -EINVAL;
	121	goto out;
	122	}
	123
	124	dcs = dentry->d_cookie;
	125
	126	if (!dcs)
	127	dcs = alloc_dcookie(dentry, vfsmnt);
	128
	129	if (!dcs) {
	130	err = -ENOMEM;
	131	goto out;
	132	}
	133
	134	*cookie = dcookie_value(dcs);
	135
	136	out:
	137	up(&dcookie_sem);
	138	return err;
	139	}
	140
	141
	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;
	153
	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;
	159
	160	down(&dcookie_sem);
	161
	162	if (!is_live()) {
	163	err = -EINVAL;
	164	goto out;
	165	}
166
167	if (!(dcs = find_dcookie(cookie)))
168	goto out;
169
170	err = -ENOMEM;
171	kbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
172	if (!kbuf)
173	goto out;
174
175	/* FIXME: (deleted) ? */
176	path = d_path(dcs->dentry, dcs->vfsmnt, kbuf, PAGE_SIZE);
177
178	if (IS_ERR(path)) {
179	err = PTR_ERR(path);
180	goto out_free;
181	}
182
183	err = -ERANGE;
184
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	}
191
192	out_free:
193	kfree(kbuf);
194	out:
195	up(&dcookie_sem);
196	return err;
197	}
198
199
200	static int dcookie_init(void)
201	{
202	struct list_head * d;
203	unsigned int i, hash_bits;
204	int err = -ENOMEM;
205
206	dcookie_cache = kmem_cache_create("dcookie_cache",
207	sizeof(struct dcookie_struct),
208	0, 0, NULL, NULL);
209
210	if (!dcookie_cache)
211	goto out;
212
213	dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
214	if (!dcookie_hashtable)
215	goto out_kmem;
216
217	err = 0;
218
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--;
230
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;
236
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);
245
246	out:
247	return err;
248	out_kmem:
249	kmem_cache_destroy(dcookie_cache);
250	goto out;
251	}
252
253
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	}
261
262
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;
270
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	}
279
280	kfree(dcookie_hashtable);
281	kmem_cache_destroy(dcookie_cache);
282	}
283
284
285	struct dcookie_user {
286	struct list_head next;
287	};
288
289	struct dcookie_user * dcookie_register(void)
290	{
291	struct dcookie_user * user;
292
293	down(&dcookie_sem);
294
295	user = kmalloc(sizeof(struct dcookie_user), GFP_KERNEL);
296	if (!user)
297	goto out;
298
299	if (!is_live() && dcookie_init())
300	goto out_free;
301
302	list_add(&user->next, &dcookie_users);
303
304	out:
305	up(&dcookie_sem);
306	return user;
307	out_free:
308	kfree(user);
309	user = NULL;
310	goto out;
311	}
312
313
314	void dcookie_unregister(struct dcookie_user * user)
315	{
316	down(&dcookie_sem);
317
318	list_del(&user->next);
319	kfree(user);
320
321	if (!is_live())
322	dcookie_exit();
323
324	up(&dcookie_sem);
325	}
326
327	EXPORT_SYMBOL_GPL(dcookie_register);
328	EXPORT_SYMBOL_GPL(dcookie_unregister);
329	EXPORT_SYMBOL_GPL(get_dcookie);