original development tree for Linux kernel GTP module; now long in mainline.
You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 

330 lines
7.9 KiB

/*
* 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_sd(struct sysfs_dirent *parent_sd,
struct kobject *target,
const char *name, int warn)
{
struct sysfs_dirent *target_sd = NULL;
struct sysfs_dirent *sd = NULL;
struct sysfs_addrm_cxt acxt;
enum kobj_ns_type ns_type;
int error;
BUG_ON(!name || !parent_sd);
/*
* We don't own @target and it may be removed at any time.
* Synchronize using sysfs_symlink_target_lock. See
* sysfs_remove_dir() for details.
*/
spin_lock(&sysfs_symlink_target_lock);
if (target->sd)
target_sd = sysfs_get(target->sd);
spin_unlock(&sysfs_symlink_target_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;
ns_type = sysfs_ns_type(parent_sd);
if (ns_type)
sd->s_ns = target_sd->s_ns;
sd->s_symlink.target_sd = target_sd;
target_sd = NULL; /* reference is now owned by the symlink */
sysfs_addrm_start(&acxt);
/* Symlinks must be between directories with the same ns_type */
if (!ns_type ||
(ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
if (warn)
error = sysfs_add_one(&acxt, sd, parent_sd);
else
error = __sysfs_add_one(&acxt, sd, parent_sd);
} else {
error = -EINVAL;
WARN(1, KERN_WARNING
"sysfs: symlink across ns_types %s/%s -> %s/%s\n",
parent_sd->s_name,
sd->s_name,
sd->s_symlink.target_sd->s_parent->s_name,
sd->s_symlink.target_sd->s_name);
}
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_sd - create symlink to a given object.
* @sd: directory we're creating the link in.
* @target: object we're pointing to.
* @name: name of the symlink.
*/
int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target,
const char *name)
{
return sysfs_do_create_link_sd(sd, target, name, 1);
}
static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
const char *name, int warn)
{
struct sysfs_dirent *parent_sd = NULL;
if (!kobj)
parent_sd = &sysfs_root;
else
parent_sd = kobj->sd;
if (!parent_sd)
return -EFAULT;
return sysfs_do_create_link_sd(parent_sd, target, name, warn);
}
/**
* 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);
}
EXPORT_SYMBOL_GPL(sysfs_create_link);
/**
* 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 sysfs_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;
/*
* We don't own @target and it may be removed at any time.
* Synchronize using sysfs_symlink_target_lock. See
* sysfs_remove_dir() for details.
*/
spin_lock(&sysfs_symlink_target_lock);
if (targ->sd && sysfs_ns_type(kobj->sd))
ns = targ->sd->s_ns;
spin_unlock(&sysfs_symlink_target_lock);
sysfs_hash_and_remove(kobj->sd, name, ns);
}
/**
* 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, name, NULL);
}
EXPORT_SYMBOL_GPL(sysfs_remove_link);
/**
* sysfs_rename_link_ns - 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.
* @new_ns: new namespace of the symlink.
*
* A helper function for the common rename symlink idiom.
*/
int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
const char *old, const char *new, const void *new_ns)
{
struct sysfs_dirent *parent_sd, *sd = NULL;
const void *old_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_ns(parent_sd, old, old_ns);
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;
result = sysfs_rename(sd, parent_sd, new, new_ns);
out:
sysfs_put(sd);
return result;
}
EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
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,
};