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/*
* 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 kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target)
{
struct kernfs_node *kn;
struct sysfs_addrm_cxt acxt;
int error;
kn = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
SYSFS_KOBJ_LINK);
if (!kn)
return ERR_PTR(-ENOMEM);
if (kernfs_ns_enabled(parent))
kn->s_ns = target->s_ns;
kn->s_symlink.target_kn = target;
kernfs_get(target); /* ref owned by symlink */
sysfs_addrm_start(&acxt);
error = sysfs_add_one(&acxt, kn, parent);
sysfs_addrm_finish(&acxt);
if (!error)
return kn;
kernfs_put(kn);
return ERR_PTR(error);
}
static int sysfs_get_target_path(struct kernfs_node *parent,
struct kernfs_node *target, char *path)
{
struct kernfs_node *base, *kn;
char *s = path;
int len = 0;
/* go up to the root, stop at the base */
base = parent;
while (base->s_parent) {
kn = target->s_parent;
while (kn->s_parent && base != kn)
kn = kn->s_parent;
if (base == kn)
break;
strcpy(s, "../");
s += 3;
base = base->s_parent;
}
/* determine end of target string for reverse fillup */
kn = target;
while (kn->s_parent && kn != base) {
len += strlen(kn->s_name) + 1;
kn = kn->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 */
kn = target;
while (kn->s_parent && kn != base) {
int slen = strlen(kn->s_name);
len -= slen;
strncpy(s + len, kn->s_name, slen);
if (len)
s[--len] = '/';
kn = kn->s_parent;
}
return 0;
}
static int sysfs_getlink(struct dentry *dentry, char *path)
{
struct kernfs_node *kn = dentry->d_fsdata;
struct kernfs_node *parent = kn->s_parent;
struct kernfs_node *target = kn->s_symlink.target_kn;
int error;
mutex_lock(&sysfs_mutex);
error = sysfs_get_target_path(parent, target, 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,
};
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