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![Rafael J. Wysocki](/assets/img/avatar_default.png)
The most convenient way to expose ACPI power resources lists of a device is to put symbolic links to sysfs directories representing those resources into special attribute groups in the device's sysfs directory. For this purpose, it is necessary to be able to add symbolic links to attribute groups. For this reason, add sysfs helper functions for adding/removing symbolic links to/from attribute groups, sysfs_add_link_to_group() and sysfs_remove_link_from_group(), respectively. This change set includes a build fix from David Rientjes. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
326 lines
7.6 KiB
C
326 lines
7.6 KiB
C
/*
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* fs/sysfs/symlink.c - sysfs symlink implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/fs.h>
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#include <linux/gfp.h>
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#include <linux/mount.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/namei.h>
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#include <linux/mutex.h>
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#include <linux/security.h>
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#include "sysfs.h"
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static int sysfs_do_create_link_sd(struct sysfs_dirent *parent_sd,
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struct kobject *target,
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const char *name, int warn)
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{
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struct sysfs_dirent *target_sd = NULL;
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struct sysfs_dirent *sd = NULL;
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struct sysfs_addrm_cxt acxt;
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enum kobj_ns_type ns_type;
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int error;
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BUG_ON(!name || !parent_sd);
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/* target->sd can go away beneath us but is protected with
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* sysfs_assoc_lock. Fetch target_sd from it.
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*/
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spin_lock(&sysfs_assoc_lock);
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if (target->sd)
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target_sd = sysfs_get(target->sd);
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spin_unlock(&sysfs_assoc_lock);
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error = -ENOENT;
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if (!target_sd)
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goto out_put;
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error = -ENOMEM;
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sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
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if (!sd)
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goto out_put;
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ns_type = sysfs_ns_type(parent_sd);
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if (ns_type)
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sd->s_ns = target->ktype->namespace(target);
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sd->s_symlink.target_sd = target_sd;
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target_sd = NULL; /* reference is now owned by the symlink */
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sysfs_addrm_start(&acxt, parent_sd);
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/* Symlinks must be between directories with the same ns_type */
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if (!ns_type ||
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(ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
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if (warn)
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error = sysfs_add_one(&acxt, sd);
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else
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error = __sysfs_add_one(&acxt, sd);
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} else {
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error = -EINVAL;
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WARN(1, KERN_WARNING
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"sysfs: symlink across ns_types %s/%s -> %s/%s\n",
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parent_sd->s_name,
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sd->s_name,
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sd->s_symlink.target_sd->s_parent->s_name,
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sd->s_symlink.target_sd->s_name);
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}
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sysfs_addrm_finish(&acxt);
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if (error)
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goto out_put;
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return 0;
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out_put:
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sysfs_put(target_sd);
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sysfs_put(sd);
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return error;
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}
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/**
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* sysfs_create_link_sd - create symlink to a given object.
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* @sd: directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link_sd(struct sysfs_dirent *sd, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link_sd(sd, target, name, 1);
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}
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static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
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const char *name, int warn)
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{
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struct sysfs_dirent *parent_sd = NULL;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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if (!parent_sd)
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return -EFAULT;
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return sysfs_do_create_link_sd(parent_sd, target, name, warn);
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}
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/**
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* sysfs_create_link - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*/
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int sysfs_create_link(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 1);
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}
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/**
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* sysfs_create_link_nowarn - create symlink between two objects.
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* @kobj: object whose directory we're creating the link in.
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* @target: object we're pointing to.
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* @name: name of the symlink.
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*
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* This function does the same as sysfs_create_link(), but it
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* doesn't warn if the link already exists.
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*/
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int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
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const char *name)
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{
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return sysfs_do_create_link(kobj, target, name, 0);
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}
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/**
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* sysfs_delete_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @name: name of the symlink to remove.
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*
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* Unlike sysfs_remove_link sysfs_delete_link has enough information
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* to successfully delete symlinks in tagged directories.
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*/
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void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
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const char *name)
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{
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const void *ns = NULL;
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spin_lock(&sysfs_assoc_lock);
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if (targ->sd && sysfs_ns_type(kobj->sd))
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ns = targ->sd->s_ns;
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spin_unlock(&sysfs_assoc_lock);
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sysfs_hash_and_remove(kobj->sd, ns, name);
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}
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/**
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* sysfs_remove_link - remove symlink in object's directory.
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* @kobj: object we're acting for.
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* @name: name of the symlink to remove.
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*/
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void sysfs_remove_link(struct kobject * kobj, const char * name)
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{
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struct sysfs_dirent *parent_sd = NULL;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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sysfs_hash_and_remove(parent_sd, NULL, name);
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}
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/**
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* sysfs_rename_link - rename symlink in object's directory.
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* @kobj: object we're acting for.
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* @targ: object we're pointing to.
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* @old: previous name of the symlink.
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* @new: new name of the symlink.
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*
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* A helper function for the common rename symlink idiom.
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*/
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int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
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const char *old, const char *new)
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{
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struct sysfs_dirent *parent_sd, *sd = NULL;
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const void *old_ns = NULL, *new_ns = NULL;
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int result;
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if (!kobj)
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parent_sd = &sysfs_root;
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else
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parent_sd = kobj->sd;
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if (targ->sd)
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old_ns = targ->sd->s_ns;
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result = -ENOENT;
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sd = sysfs_get_dirent(parent_sd, old_ns, old);
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if (!sd)
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goto out;
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result = -EINVAL;
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if (sysfs_type(sd) != SYSFS_KOBJ_LINK)
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goto out;
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if (sd->s_symlink.target_sd->s_dir.kobj != targ)
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goto out;
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if (sysfs_ns_type(parent_sd))
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new_ns = targ->ktype->namespace(targ);
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result = sysfs_rename(sd, parent_sd, new_ns, new);
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out:
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sysfs_put(sd);
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return result;
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}
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static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
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struct sysfs_dirent *target_sd, char *path)
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{
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struct sysfs_dirent *base, *sd;
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char *s = path;
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int len = 0;
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/* go up to the root, stop at the base */
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base = parent_sd;
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while (base->s_parent) {
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sd = target_sd->s_parent;
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while (sd->s_parent && base != sd)
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sd = sd->s_parent;
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if (base == sd)
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break;
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strcpy(s, "../");
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s += 3;
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base = base->s_parent;
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}
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/* determine end of target string for reverse fillup */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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len += strlen(sd->s_name) + 1;
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sd = sd->s_parent;
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}
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/* check limits */
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if (len < 2)
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return -EINVAL;
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len--;
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if ((s - path) + len > PATH_MAX)
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return -ENAMETOOLONG;
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/* reverse fillup of target string from target to base */
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sd = target_sd;
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while (sd->s_parent && sd != base) {
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int slen = strlen(sd->s_name);
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len -= slen;
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strncpy(s + len, sd->s_name, slen);
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if (len)
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s[--len] = '/';
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sd = sd->s_parent;
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}
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return 0;
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}
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static int sysfs_getlink(struct dentry *dentry, char * path)
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{
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struct sysfs_dirent *sd = dentry->d_fsdata;
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struct sysfs_dirent *parent_sd = sd->s_parent;
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struct sysfs_dirent *target_sd = sd->s_symlink.target_sd;
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int error;
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mutex_lock(&sysfs_mutex);
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error = sysfs_get_target_path(parent_sd, target_sd, path);
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mutex_unlock(&sysfs_mutex);
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return error;
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}
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static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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int error = -ENOMEM;
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unsigned long page = get_zeroed_page(GFP_KERNEL);
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if (page) {
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error = sysfs_getlink(dentry, (char *) page);
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if (error < 0)
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free_page((unsigned long)page);
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}
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nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
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return NULL;
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}
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static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
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{
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char *page = nd_get_link(nd);
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if (!IS_ERR(page))
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free_page((unsigned long)page);
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}
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const struct inode_operations sysfs_symlink_inode_operations = {
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.setxattr = sysfs_setxattr,
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.readlink = generic_readlink,
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.follow_link = sysfs_follow_link,
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.put_link = sysfs_put_link,
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.setattr = sysfs_setattr,
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.getattr = sysfs_getattr,
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.permission = sysfs_permission,
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};
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EXPORT_SYMBOL_GPL(sysfs_create_link);
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EXPORT_SYMBOL_GPL(sysfs_remove_link);
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EXPORT_SYMBOL_GPL(sysfs_rename_link);
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