[net-next-2.6.git] / fs / sysfs / symlink.c

/*
 * fs/sysfs/symlink.c - sysfs symlink implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
 *
 * This file is released under the GPLv2.
 *
 * Please see Documentation/filesystems/sysfs.txt for more information.
 */

#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <linux/mutex.h>
#include <linux/security.h>

#include "sysfs.h"

static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
				const char *name, int warn)
{
	struct sysfs_dirent *parent_sd = NULL;
	struct sysfs_dirent *target_sd = NULL;
	struct sysfs_dirent *sd = NULL;
	struct sysfs_addrm_cxt acxt;
	int error;

	BUG_ON(!name);

	if (!kobj)
		parent_sd = &sysfs_root;
	else
		parent_sd = kobj->sd;

	error = -EFAULT;
	if (!parent_sd)
		goto out_put;

	/* target->sd can go away beneath us but is protected with
	 * sysfs_assoc_lock.  Fetch target_sd from it.
	 */
	spin_lock(&sysfs_assoc_lock);
	if (target->sd)
		target_sd = sysfs_get(target->sd);
	spin_unlock(&sysfs_assoc_lock);

	error = -ENOENT;
	if (!target_sd)
		goto out_put;

	error = -ENOMEM;
	sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
	if (!sd)
		goto out_put;

	if (sysfs_ns_type(parent_sd))
		sd->s_ns = target->ktype->namespace(target);
	sd->s_symlink.target_sd = target_sd;
	target_sd = NULL;	/* reference is now owned by the symlink */

	sysfs_addrm_start(&acxt, parent_sd);
	if (warn)
		error = sysfs_add_one(&acxt, sd);
	else
		error = __sysfs_add_one(&acxt, sd);
	sysfs_addrm_finish(&acxt);

	if (error)
		goto out_put;

	return 0;

 out_put:
	sysfs_put(target_sd);
	sysfs_put(sd);
	return error;
}

/**
 *	sysfs_create_link - create symlink between two objects.
 *	@kobj:	object whose directory we're creating the link in.
 *	@target:	object we're pointing to.
 *	@name:		name of the symlink.
 */
int sysfs_create_link(struct kobject *kobj, struct kobject *target,
		      const char *name)
{
	return sysfs_do_create_link(kobj, target, name, 1);
}

/**
 *	sysfs_create_link_nowarn - create symlink between two objects.
 *	@kobj:	object whose directory we're creating the link in.
 *	@target:	object we're pointing to.
 *	@name:		name of the symlink.
 *
 *	This function does the same as sysf_create_link(), but it
 *	doesn't warn if the link already exists.
 */
int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
			     const char *name)
{
	return sysfs_do_create_link(kobj, target, name, 0);
}

/**
 *	sysfs_delete_link - remove symlink in object's directory.
 *	@kobj:	object we're acting for.
 *	@targ:	object we're pointing to.
 *	@name:	name of the symlink to remove.
 *
 *	Unlike sysfs_remove_link sysfs_delete_link has enough information
 *	to successfully delete symlinks in tagged directories.
 */
void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
			const char *name)
{
	const void *ns = NULL;
	spin_lock(&sysfs_assoc_lock);
	if (targ->sd)
		ns = targ->sd->s_ns;
	spin_unlock(&sysfs_assoc_lock);
	sysfs_hash_and_remove(kobj->sd, ns, name);
}

/**
 *	sysfs_remove_link - remove symlink in object's directory.
 *	@kobj:	object we're acting for.
 *	@name:	name of the symlink to remove.
 */

void sysfs_remove_link(struct kobject * kobj, const char * name)
{
	struct sysfs_dirent *parent_sd = NULL;

	if (!kobj)
		parent_sd = &sysfs_root;
	else
		parent_sd = kobj->sd;

	sysfs_hash_and_remove(parent_sd, NULL, name);
}

/**
 *	sysfs_rename_link - rename symlink in object's directory.
 *	@kobj:	object we're acting for.
 *	@targ:	object we're pointing to.
 *	@old:	previous name of the symlink.
 *	@new:	new name of the symlink.
 *
 *	A helper function for the common rename symlink idiom.
 */
int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
			const char *old, const char *new)
{
	struct sysfs_dirent *parent_sd, *sd = NULL;
	const void *old_ns = NULL, *new_ns = NULL;
	int result;

	if (!kobj)
		parent_sd = &sysfs_root;
	else
		parent_sd = kobj->sd;

	if (targ->sd)
		old_ns = targ->sd->s_ns;

	result = -ENOENT;
	sd = sysfs_get_dirent(parent_sd, old_ns, old);
	if (!sd)
		goto out;

	result = -EINVAL;
	if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
		goto out;
	if (sd->s_symlink.target_sd->s_dir.kobj != targ)
		goto out;

	if (sysfs_ns_type(parent_sd))
		new_ns = targ->ktype->namespace(targ);

	result = sysfs_rename(sd, parent_sd, new_ns, new);

out:
	sysfs_put(sd);
	return result;
}

static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
				 struct sysfs_dirent *target_sd, char *path)
{
	struct sysfs_dirent *base, *sd;
	char *s = path;
	int len = 0;

	/* go up to the root, stop at the base */
	base = parent_sd;
	while (base->s_parent) {
		sd = target_sd->s_parent;
		while (sd->s_parent && base != sd)
			sd = sd->s_parent;

		if (base == sd)
			break;

		strcpy(s, "../");
		s += 3;
		base = base->s_parent;
	}

	/* determine end of target string for reverse fillup */
	sd = target_sd;
	while (sd->s_parent && sd != base) {
		len += strlen(sd->s_name) + 1;
		sd = sd->s_parent;
	}

	/* check limits */
	if (len < 2)
		return -EINVAL;
	len--;
	if ((s - path) + len > PATH_MAX)
		return -ENAMETOOLONG;

	/* reverse fillup of target string from target to base */
	sd = target_sd;
	while (sd->s_parent && sd != base) {
		int slen = strlen(sd->s_name);

		len -= slen;
		strncpy(s + len, sd->s_name, slen);
		if (len)
			s[--len] = '/';

		sd = sd->s_parent;
	}

	return 0;
}

static int sysfs_getlink(struct dentry *dentry, char * path)
{
	struct sysfs_dirent *sd = dentry->d_fsdata;
	struct sysfs_dirent *parent_sd = sd->s_parent;
	struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
	int error;

	mutex_lock(&sysfs_mutex);
	error = sysfs_get_target_path(parent_sd, target_sd, path);
	mutex_unlock(&sysfs_mutex);

	return error;
}

static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	int error = -ENOMEM;
	unsigned long page = get_zeroed_page(GFP_KERNEL);
	if (page) {
		error = sysfs_getlink(dentry, (char *) page); 
		if (error < 0)
			free_page((unsigned long)page);
	}
	nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
	return NULL;
}

static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
	char *page = nd_get_link(nd);
	if (!IS_ERR(page))
		free_page((unsigned long)page);
}

const struct inode_operations sysfs_symlink_inode_operations = {
	.setxattr	= sysfs_setxattr,
	.readlink	= generic_readlink,
	.follow_link	= sysfs_follow_link,
	.put_link	= sysfs_put_link,
	.setattr	= sysfs_setattr,
	.getattr	= sysfs_getattr,
	.permission	= sysfs_permission,
};


EXPORT_SYMBOL_GPL(sysfs_create_link);
EXPORT_SYMBOL_GPL(sysfs_remove_link);
EXPORT_SYMBOL_GPL(sysfs_rename_link);
Commit	Line	Data
1da177e4	1	/*
6d66f5cd TH	2	* fs/sysfs/symlink.c - sysfs symlink implementation
	3	*
	4	* Copyright (c) 2001-3 Patrick Mochel
	5	* Copyright (c) 2007 SUSE Linux Products GmbH
	6	* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
	7	*
	8	* This file is released under the GPLv2.
	9	*
	10	* Please see Documentation/filesystems/sysfs.txt for more information.
1da177e4 LT	11	*/
	12
	13	#include <linux/fs.h>
5a0e3ad6	14	#include <linux/gfp.h>
ceeee1fb	15	#include <linux/mount.h>
1da177e4 LT	16	#include <linux/module.h>
	17	#include <linux/kobject.h>
	18	#include <linux/namei.h>
869512ab	19	#include <linux/mutex.h>
ddd29ec6	20	#include <linux/security.h>
1da177e4 LT	21
	22	#include "sysfs.h"
	23
36ce6dad CH	24	static int sysfs_do_create_link(struct kobject kobj, struct kobject target,
36ce6dad CH	25	const char *name, int warn)
1da177e4	26	{
2b29ac25 TH	27	struct sysfs_dirent *parent_sd = NULL;
2b29ac25 TH	28	struct sysfs_dirent *target_sd = NULL;
3007e997	29	struct sysfs_dirent *sd = NULL;
fb6896da	30	struct sysfs_addrm_cxt acxt;
3007e997	31	int error;
1da177e4	32
ceeee1fb GKH	33	BUG_ON(!name);
ceeee1fb GKH	34
7d0c7d67 EB	35	if (!kobj)
	36	parent_sd = &sysfs_root;
	37	else
608e266a	38	parent_sd = kobj->sd;
ceeee1fb	39
3007e997	40	error = -EFAULT;
608e266a	41	if (!parent_sd)
3007e997	42	goto out_put;
2b29ac25	43
608e266a	44	/* target->sd can go away beneath us but is protected with
5f995323	45	* sysfs_assoc_lock. Fetch target_sd from it.
2b29ac25	46	*/
5f995323	47	spin_lock(&sysfs_assoc_lock);
608e266a TH	48	if (target->sd)
608e266a TH	49	target_sd = sysfs_get(target->sd);
5f995323	50	spin_unlock(&sysfs_assoc_lock);
2b29ac25	51
3007e997	52	error = -ENOENT;
2b29ac25	53	if (!target_sd)
3007e997 TH	54	goto out_put;
	55
	56	error = -ENOMEM;
	57	sd = sysfs_new_dirent(name, S_IFLNK\|S_IRWXUGO, SYSFS_KOBJ_LINK);
	58	if (!sd)
	59	goto out_put;
a1da4dfe	60
3ff195b0 EB	61	if (sysfs_ns_type(parent_sd))
3ff195b0 EB	62	sd->s_ns = target->ktype->namespace(target);
b1fc3d61	63	sd->s_symlink.target_sd = target_sd;
a1da4dfe	64	target_sd = NULL; /* reference is now owned by the symlink */
1da177e4	65
fb6896da	66	sysfs_addrm_start(&acxt, parent_sd);
36ce6dad CH	67	if (warn)
	68	error = sysfs_add_one(&acxt, sd);
	69	else
	70	error = __sysfs_add_one(&acxt, sd);
23dc2799	71	sysfs_addrm_finish(&acxt);
2b29ac25	72
23dc2799	73	if (error)
967e35dc	74	goto out_put;
967e35dc TH	75
967e35dc TH	76	return 0;
fb6896da	77
3007e997 TH	78	out_put:
	79	sysfs_put(target_sd);
	80	sysfs_put(sd);
1da177e4 LT	81	return error;
	82	}
	83
36ce6dad CH	84	/**
	85	* sysfs_create_link - create symlink between two objects.
	86	* @kobj: object whose directory we're creating the link in.
	87	* @target: object we're pointing to.
	88	* @name: name of the symlink.
	89	*/
	90	int sysfs_create_link(struct kobject kobj, struct kobject target,
	91	const char *name)
	92	{
	93	return sysfs_do_create_link(kobj, target, name, 1);
	94	}
	95
	96	/**
	97	* sysfs_create_link_nowarn - create symlink between two objects.
	98	* @kobj: object whose directory we're creating the link in.
	99	* @target: object we're pointing to.
	100	* @name: name of the symlink.
	101	*
	102	* This function does the same as sysf_create_link(), but it
	103	* doesn't warn if the link already exists.
	104	*/
	105	int sysfs_create_link_nowarn(struct kobject kobj, struct kobject target,
	106	const char *name)
	107	{
	108	return sysfs_do_create_link(kobj, target, name, 0);
	109	}
	110
746edb7a EB	111	/**
	112	* sysfs_delete_link - remove symlink in object's directory.
	113	* @kobj: object we're acting for.
	114	* @targ: object we're pointing to.
	115	* @name: name of the symlink to remove.
	116	*
	117	* Unlike sysfs_remove_link sysfs_delete_link has enough information
	118	* to successfully delete symlinks in tagged directories.
	119	*/
	120	void sysfs_delete_link(struct kobject kobj, struct kobject targ,
	121	const char *name)
	122	{
	123	const void *ns = NULL;
	124	spin_lock(&sysfs_assoc_lock);
	125	if (targ->sd)
	126	ns = targ->sd->s_ns;
	127	spin_unlock(&sysfs_assoc_lock);
	128	sysfs_hash_and_remove(kobj->sd, ns, name);
	129	}
	130
1da177e4 LT	131	/**
	132	* sysfs_remove_link - remove symlink in object's directory.
	133	* @kobj: object we're acting for.
	134	* @name: name of the symlink to remove.
	135	*/
	136
e3a15db2	137	void sysfs_remove_link(struct kobject * kobj, const char * name)
1da177e4	138	{
a839c5af MF	139	struct sysfs_dirent *parent_sd = NULL;
	140
	141	if (!kobj)
	142	parent_sd = &sysfs_root;
	143	else
	144	parent_sd = kobj->sd;
	145
3ff195b0	146	sysfs_hash_and_remove(parent_sd, NULL, name);
1da177e4 LT	147	}
1da177e4 LT	148
7cb32942 EB	149	/**
	150	* sysfs_rename_link - rename symlink in object's directory.
	151	* @kobj: object we're acting for.
	152	* @targ: object we're pointing to.
	153	* @old: previous name of the symlink.
	154	* @new: new name of the symlink.
	155	*
	156	* A helper function for the common rename symlink idiom.
	157	*/
	158	int sysfs_rename_link(struct kobject kobj, struct kobject targ,
	159	const char old, const char new)
	160	{
	161	struct sysfs_dirent parent_sd, sd = NULL;
3ff195b0	162	const void old_ns = NULL, new_ns = NULL;
7cb32942 EB	163	int result;
	164
	165	if (!kobj)
	166	parent_sd = &sysfs_root;
	167	else
	168	parent_sd = kobj->sd;
	169
3ff195b0 EB	170	if (targ->sd)
	171	old_ns = targ->sd->s_ns;
	172
7cb32942	173	result = -ENOENT;
3ff195b0	174	sd = sysfs_get_dirent(parent_sd, old_ns, old);
7cb32942 EB	175	if (!sd)
	176	goto out;
	177
	178	result = -EINVAL;
	179	if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
	180	goto out;
	181	if (sd->s_symlink.target_sd->s_dir.kobj != targ)
	182	goto out;
	183
3ff195b0 EB	184	if (sysfs_ns_type(parent_sd))
	185	new_ns = targ->ktype->namespace(targ);
	186
	187	result = sysfs_rename(sd, parent_sd, new_ns, new);
7cb32942 EB	188
	189	out:
	190	sysfs_put(sd);
	191	return result;
	192	}
	193
2f90a851 KS	194	static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
2f90a851 KS	195	struct sysfs_dirent target_sd, char path)
1da177e4	196	{
2f90a851 KS	197	struct sysfs_dirent base, sd;
	198	char *s = path;
	199	int len = 0;
	200
	201	/* go up to the root, stop at the base */
	202	base = parent_sd;
	203	while (base->s_parent) {
	204	sd = target_sd->s_parent;
	205	while (sd->s_parent && base != sd)
	206	sd = sd->s_parent;
	207
	208	if (base == sd)
	209	break;
	210
	211	strcpy(s, "../");
	212	s += 3;
	213	base = base->s_parent;
	214	}
	215
	216	/* determine end of target string for reverse fillup */
	217	sd = target_sd;
	218	while (sd->s_parent && sd != base) {
	219	len += strlen(sd->s_name) + 1;
	220	sd = sd->s_parent;
	221	}
1da177e4	222
2f90a851 KS	223	/* check limits */
	224	if (len < 2)
	225	return -EINVAL;
	226	len--;
	227	if ((s - path) + len > PATH_MAX)
1da177e4 LT	228	return -ENAMETOOLONG;
1da177e4 LT	229
2f90a851 KS	230	/* reverse fillup of target string from target to base */
	231	sd = target_sd;
	232	while (sd->s_parent && sd != base) {
	233	int slen = strlen(sd->s_name);
1da177e4	234
2f90a851 KS	235	len -= slen;
	236	strncpy(s + len, sd->s_name, slen);
	237	if (len)
	238	s[--len] = '/';
1da177e4	239
2f90a851 KS	240	sd = sd->s_parent;
2f90a851 KS	241	}
1da177e4 LT	242
	243	return 0;
	244	}
	245
	246	static int sysfs_getlink(struct dentry dentry, char path)
	247	{
2b29ac25 TH	248	struct sysfs_dirent *sd = dentry->d_fsdata;
2b29ac25 TH	249	struct sysfs_dirent *parent_sd = sd->s_parent;
b1fc3d61	250	struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
2b29ac25	251	int error;
1da177e4	252
3007e997	253	mutex_lock(&sysfs_mutex);
2b29ac25	254	error = sysfs_get_target_path(parent_sd, target_sd, path);
3007e997	255	mutex_unlock(&sysfs_mutex);
1da177e4	256
2b29ac25	257	return error;
1da177e4 LT	258	}
1da177e4 LT	259
cc314eef	260	static void sysfs_follow_link(struct dentry dentry, struct nameidata *nd)
1da177e4 LT	261	{
	262	int error = -ENOMEM;
	263	unsigned long page = get_zeroed_page(GFP_KERNEL);
557411eb	264	if (page) {
1da177e4	265	error = sysfs_getlink(dentry, (char *) page);
557411eb AK	266	if (error < 0)
	267	free_page((unsigned long)page);
	268	}
1da177e4	269	nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
cc314eef	270	return NULL;
1da177e4 LT	271	}
1da177e4 LT	272
cc314eef	273	static void sysfs_put_link(struct dentry dentry, struct nameidata nd, void *cookie)
1da177e4 LT	274	{
	275	char *page = nd_get_link(nd);
	276	if (!IS_ERR(page))
	277	free_page((unsigned long)page);
	278	}
	279
c5ef1c42	280	const struct inode_operations sysfs_symlink_inode_operations = {
c099aacd EB	281	.setxattr = sysfs_setxattr,
	282	.readlink = generic_readlink,
	283	.follow_link = sysfs_follow_link,
	284	.put_link = sysfs_put_link,
e61ab4ae EB	285	.setattr = sysfs_setattr,
	286	.getattr = sysfs_getattr,
	287	.permission = sysfs_permission,
1da177e4 LT	288	};
	289
	290
	291	EXPORT_SYMBOL_GPL(sysfs_create_link);
	292	EXPORT_SYMBOL_GPL(sysfs_remove_link);
e0f43752	293	EXPORT_SYMBOL_GPL(sysfs_rename_link);