[mirror_ubuntu-artful-kernel.git] / fs / kernfs / symlink.c

/*
 * fs/kernfs/symlink.c - kernfs symlink implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 */

#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/namei.h>

#include "kernfs-internal.h"

/**
 * kernfs_create_link - create a symlink
 * @parent: directory to create the symlink in
 * @name: name of the symlink
 * @target: target node for the symlink to point to
 *
 * Returns the created node on success, ERR_PTR() value on error.
 */
struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
					const char *name,
					struct sysfs_dirent *target)
{
	struct sysfs_dirent *sd;
	struct sysfs_addrm_cxt acxt;
	int error;

	sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
			      SYSFS_KOBJ_LINK);
	if (!sd)
		return ERR_PTR(-ENOMEM);

	if (kernfs_ns_enabled(parent))
		sd->s_ns = target->s_ns;
	sd->s_symlink.target_sd = target;
	kernfs_get(target);	/* ref owned by symlink */

	sysfs_addrm_start(&acxt);
	error = sysfs_add_one(&acxt, sd, parent);
	sysfs_addrm_finish(&acxt);

	if (!error)
		return sd;

	kernfs_put(sd);
	return ERR_PTR(error);
}

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,
	.removexattr	= sysfs_removexattr,
	.getxattr	= sysfs_getxattr,
	.listxattr	= sysfs_listxattr,
	.readlink	= generic_readlink,
	.follow_link	= sysfs_follow_link,
	.put_link	= sysfs_put_link,
	.setattr	= sysfs_setattr,
	.getattr	= sysfs_getattr,
	.permission	= sysfs_permission,
};
Commit	Line	Data
b8441ed2 TH	1	/*
	2	* fs/kernfs/symlink.c - kernfs symlink implementation
	3	*
	4	* Copyright (c) 2001-3 Patrick Mochel
	5	* Copyright (c) 2007 SUSE Linux Products GmbH
	6	* Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
	7	*
	8	* This file is released under the GPLv2.
	9	*/
2072f1af TH	10
	11	#include <linux/fs.h>
	12	#include <linux/gfp.h>
	13	#include <linux/namei.h>
	14
	15	#include "kernfs-internal.h"
	16
	17	/**
	18	* kernfs_create_link - create a symlink
	19	* @parent: directory to create the symlink in
	20	* @name: name of the symlink
	21	* @target: target node for the symlink to point to
	22	*
	23	* Returns the created node on success, ERR_PTR() value on error.
	24	*/
	25	struct sysfs_dirent kernfs_create_link(struct sysfs_dirent parent,
	26	const char *name,
	27	struct sysfs_dirent *target)
	28	{
	29	struct sysfs_dirent *sd;
	30	struct sysfs_addrm_cxt acxt;
	31	int error;
	32
bc755553 TH	33	sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK\|S_IRWXUGO,
bc755553 TH	34	SYSFS_KOBJ_LINK);
2072f1af TH	35	if (!sd)
	36	return ERR_PTR(-ENOMEM);
	37
ac9bba03	38	if (kernfs_ns_enabled(parent))
2072f1af TH	39	sd->s_ns = target->s_ns;
	40	sd->s_symlink.target_sd = target;
	41	kernfs_get(target); /* ref owned by symlink */
	42
	43	sysfs_addrm_start(&acxt);
	44	error = sysfs_add_one(&acxt, sd, parent);
	45	sysfs_addrm_finish(&acxt);
	46
	47	if (!error)
	48	return sd;
	49
	50	kernfs_put(sd);
	51	return ERR_PTR(error);
	52	}
	53
	54	static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
	55	struct sysfs_dirent target_sd, char path)
	56	{
	57	struct sysfs_dirent base, sd;
	58	char *s = path;
	59	int len = 0;
	60
	61	/* go up to the root, stop at the base */
	62	base = parent_sd;
	63	while (base->s_parent) {
	64	sd = target_sd->s_parent;
	65	while (sd->s_parent && base != sd)
	66	sd = sd->s_parent;
	67
	68	if (base == sd)
	69	break;
	70
	71	strcpy(s, "../");
	72	s += 3;
	73	base = base->s_parent;
	74	}
	75
	76	/* determine end of target string for reverse fillup */
	77	sd = target_sd;
	78	while (sd->s_parent && sd != base) {
	79	len += strlen(sd->s_name) + 1;
	80	sd = sd->s_parent;
	81	}
	82
	83	/* check limits */
	84	if (len < 2)
	85	return -EINVAL;
	86	len--;
	87	if ((s - path) + len > PATH_MAX)
	88	return -ENAMETOOLONG;
	89
	90	/* reverse fillup of target string from target to base */
	91	sd = target_sd;
	92	while (sd->s_parent && sd != base) {
	93	int slen = strlen(sd->s_name);
	94
	95	len -= slen;
	96	strncpy(s + len, sd->s_name, slen);
	97	if (len)
	98	s[--len] = '/';
	99
	100	sd = sd->s_parent;
	101	}
	102
103	return 0;
104	}
105
106	static int sysfs_getlink(struct dentry dentry, char path)
107	{
108	struct sysfs_dirent *sd = dentry->d_fsdata;
109	struct sysfs_dirent *parent_sd = sd->s_parent;
110	struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
111	int error;
112
113	mutex_lock(&sysfs_mutex);
114	error = sysfs_get_target_path(parent_sd, target_sd, path);
115	mutex_unlock(&sysfs_mutex);
116
117	return error;
118	}
119
120	static void sysfs_follow_link(struct dentry dentry, struct nameidata *nd)
121	{
122	int error = -ENOMEM;
123	unsigned long page = get_zeroed_page(GFP_KERNEL);
124	if (page) {
125	error = sysfs_getlink(dentry, (char *) page);
126	if (error < 0)
127	free_page((unsigned long)page);
128	}
129	nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
130	return NULL;
131	}
132
133	static void sysfs_put_link(struct dentry dentry, struct nameidata nd,
134	void *cookie)
135	{
136	char *page = nd_get_link(nd);
137	if (!IS_ERR(page))
138	free_page((unsigned long)page);
139	}
140
141	const struct inode_operations sysfs_symlink_inode_operations = {
142	.setxattr = sysfs_setxattr,
2322392b TH	143	.removexattr = sysfs_removexattr,
	144	.getxattr = sysfs_getxattr,
	145	.listxattr = sysfs_listxattr,
2072f1af TH	146	.readlink = generic_readlink,
	147	.follow_link = sysfs_follow_link,
	148	.put_link = sysfs_put_link,
	149	.setattr = sysfs_setattr,
	150	.getattr = sysfs_getattr,
	151	.permission = sysfs_permission,
	152	};