148 lines
3.3 KiB
C
148 lines
3.3 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 kernfs_node *kernfs_create_link(struct kernfs_node *parent,
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const char *name,
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struct kernfs_node *target)
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{
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struct kernfs_node *kn;
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int error;
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kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK);
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if (!kn)
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return ERR_PTR(-ENOMEM);
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if (kernfs_ns_enabled(parent))
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kn->ns = target->ns;
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kn->symlink.target_kn = target;
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kernfs_get(target); /* ref owned by symlink */
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error = kernfs_add_one(kn);
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if (!error)
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return kn;
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kernfs_put(kn);
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return ERR_PTR(error);
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}
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static int kernfs_get_target_path(struct kernfs_node *parent,
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struct kernfs_node *target, char *path)
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{
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struct kernfs_node *base, *kn;
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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;
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while (base->parent) {
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kn = target->parent;
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while (kn->parent && base != kn)
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kn = kn->parent;
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if (base == kn)
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break;
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strcpy(s, "../");
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s += 3;
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base = base->parent;
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}
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/* determine end of target string for reverse fillup */
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kn = target;
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while (kn->parent && kn != base) {
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len += strlen(kn->name) + 1;
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kn = kn->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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kn = target;
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while (kn->parent && kn != base) {
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int slen = strlen(kn->name);
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len -= slen;
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strncpy(s + len, kn->name, slen);
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if (len)
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s[--len] = '/';
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kn = kn->parent;
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}
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return 0;
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}
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static int kernfs_getlink(struct dentry *dentry, char *path)
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{
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struct kernfs_node *kn = dentry->d_fsdata;
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struct kernfs_node *parent = kn->parent;
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struct kernfs_node *target = kn->symlink.target_kn;
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int error;
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mutex_lock(&kernfs_mutex);
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error = kernfs_get_target_path(parent, target, path);
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mutex_unlock(&kernfs_mutex);
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return error;
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}
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static void *kernfs_iop_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 = kernfs_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 kernfs_iop_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 kernfs_symlink_iops = {
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.setxattr = kernfs_iop_setxattr,
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.removexattr = kernfs_iop_removexattr,
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.getxattr = kernfs_iop_getxattr,
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.listxattr = kernfs_iop_listxattr,
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.readlink = generic_readlink,
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.follow_link = kernfs_iop_follow_link,
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.put_link = kernfs_iop_put_link,
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.setattr = kernfs_iop_setattr,
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.getattr = kernfs_iop_getattr,
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.permission = kernfs_iop_permission,
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};
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