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/*
* symlink.c - operations for sysfs symlinks.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <asm/semaphore.h>
#include "sysfs.h"
static int object_depth(struct sysfs_dirent *sd)
{
int depth = 0;
for (; sd->s_parent; sd = sd->s_parent)
depth++;
return depth;
}
static int object_path_length(struct sysfs_dirent * sd)
{
int length = 1;
for (; sd->s_parent; sd = sd->s_parent)
length += strlen(sd->s_name) + 1;
return length;
}
static void fill_object_path(struct sysfs_dirent *sd, char *buffer, int length)
{
--length;
for (; sd->s_parent; sd = sd->s_parent) {
int cur = strlen(sd->s_name);
/* back up enough to print this bus id with '/' */
length -= cur;
strncpy(buffer + length, sd->s_name, cur);
*(buffer + --length) = '/';
}
}
static int sysfs_add_link(struct sysfs_dirent * parent_sd, const char * name,
struct sysfs_dirent * target_sd)
{
struct sysfs_dirent * sd;
sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
if (!sd)
return -ENOMEM;
sd->s_elem.symlink.target_sd = target_sd;
sysfs_attach_dirent(sd, parent_sd, NULL);
return 0;
}
/**
* 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)
{
struct sysfs_dirent *parent_sd = NULL;
struct sysfs_dirent *target_sd = NULL;
int error = -EEXIST;
BUG_ON(!name);
if (!kobj) {
if (sysfs_mount && sysfs_mount->mnt_sb)
parent_sd = sysfs_mount->mnt_sb->s_root->d_fsdata;
} else
parent_sd = kobj->sd;
if (!parent_sd)
return -EFAULT;
/* target->sd can go away beneath us but is protected with
* kobj_sysfs_assoc_lock. Fetch target_sd from it.
*/
spin_lock(&kobj_sysfs_assoc_lock);
if (target->sd)
target_sd = sysfs_get(target->sd);
spin_unlock(&kobj_sysfs_assoc_lock);
if (!target_sd)
return -ENOENT;
mutex_lock(&parent_sd->s_dentry->d_inode->i_mutex);
if (!sysfs_find_dirent(parent_sd, name))
error = sysfs_add_link(parent_sd, name, target_sd);
mutex_unlock(&parent_sd->s_dentry->d_inode->i_mutex);
if (error)
sysfs_put(target_sd);
return error;
}
/**
* 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)
{
sysfs_hash_and_remove(kobj->sd, name);
}
static int sysfs_get_target_path(struct sysfs_dirent * parent_sd,
struct sysfs_dirent * target_sd, char *path)
{
char * s;
int depth, size;
depth = object_depth(parent_sd);
size = object_path_length(target_sd) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_object_path(target_sd, path, size);
pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
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_elem.symlink.target_sd;
int error;
down_read(&sysfs_rename_sem);
error = sysfs_get_target_path(parent_sd, target_sd, path);
up_read(&sysfs_rename_sem);
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);
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 = {
.readlink = generic_readlink,
.follow_link = sysfs_follow_link,
.put_link = sysfs_put_link,
};
EXPORT_SYMBOL_GPL(sysfs_create_link);
EXPORT_SYMBOL_GPL(sysfs_remove_link);
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