| /* |
| * 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; |
| 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; |
| |
| if (parent_sd->s_flags & SYSFS_FLAG_NS) |
| 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); |
| if (warn) |
| error = sysfs_add_one(&acxt, sd, parent_sd); |
| else |
| error = __sysfs_add_one(&acxt, sd, parent_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_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 && (kobj->sd->s_flags & SYSFS_FLAG_NS)) |
| 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, |
| }; |