153 lines
3.4 KiB
C
153 lines
3.4 KiB
C
/*
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* fs/kernfs/symlink.c - kernfs 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, 2013 Tejun Heo <tj@kernel.org>
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*
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* This file is released under the GPLv2.
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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/namei.h>
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#include "kernfs-internal.h"
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/**
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* kernfs_create_link - create a symlink
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* @parent: directory to create the symlink in
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* @name: name of the symlink
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* @target: target node for the symlink to point to
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*
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* Returns the created node on success, ERR_PTR() value on error.
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*/
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struct sysfs_dirent *kernfs_create_link(struct sysfs_dirent *parent,
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const char *name,
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struct sysfs_dirent *target)
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{
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struct sysfs_dirent *sd;
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struct sysfs_addrm_cxt acxt;
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int error;
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sd = sysfs_new_dirent(kernfs_root(parent), name, S_IFLNK|S_IRWXUGO,
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SYSFS_KOBJ_LINK);
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if (!sd)
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return ERR_PTR(-ENOMEM);
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if (kernfs_ns_enabled(parent))
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sd->s_ns = target->s_ns;
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sd->s_symlink.target_sd = target;
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kernfs_get(target); /* ref owned by symlink */
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sysfs_addrm_start(&acxt);
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error = sysfs_add_one(&acxt, sd, parent);
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sysfs_addrm_finish(&acxt);
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if (!error)
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return sd;
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kernfs_put(sd);
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return ERR_PTR(error);
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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,
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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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.removexattr = sysfs_removexattr,
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.getxattr = sysfs_getxattr,
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.listxattr = sysfs_listxattr,
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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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