| /* |
| * fs/kernfs/symlink.c - kernfs symlink implementation |
| * |
| * Copyright (c) 2001-3 Patrick Mochel |
| * Copyright (c) 2007 SUSE Linux Products GmbH |
| * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> |
| * |
| * This file is released under the GPLv2. |
| */ |
| |
| #include <linux/fs.h> |
| #include <linux/gfp.h> |
| #include <linux/namei.h> |
| |
| #include "kernfs-internal.h" |
| |
| /** |
| * kernfs_create_link - create a symlink |
| * @parent: directory to create the symlink in |
| * @name: name of the symlink |
| * @target: target node for the symlink to point to |
| * |
| * Returns the created node on success, ERR_PTR() value on error. |
| */ |
| struct kernfs_node *kernfs_create_link(struct kernfs_node *parent, |
| const char *name, |
| struct kernfs_node *target) |
| { |
| struct kernfs_node *kn; |
| int error; |
| |
| kn = kernfs_new_node(parent, name, S_IFLNK|S_IRWXUGO, KERNFS_LINK); |
| if (!kn) |
| return ERR_PTR(-ENOMEM); |
| |
| if (kernfs_ns_enabled(parent)) |
| kn->ns = target->ns; |
| kn->symlink.target_kn = target; |
| kernfs_get(target); /* ref owned by symlink */ |
| |
| error = kernfs_add_one(kn); |
| if (!error) |
| return kn; |
| |
| kernfs_put(kn); |
| return ERR_PTR(error); |
| } |
| |
| static int kernfs_get_target_path(struct kernfs_node *parent, |
| struct kernfs_node *target, char *path) |
| { |
| struct kernfs_node *base, *kn; |
| char *s = path; |
| int len = 0; |
| |
| /* go up to the root, stop at the base */ |
| base = parent; |
| while (base->parent) { |
| kn = target->parent; |
| while (kn->parent && base != kn) |
| kn = kn->parent; |
| |
| if (base == kn) |
| break; |
| |
| strcpy(s, "../"); |
| s += 3; |
| base = base->parent; |
| } |
| |
| /* determine end of target string for reverse fillup */ |
| kn = target; |
| while (kn->parent && kn != base) { |
| len += strlen(kn->name) + 1; |
| kn = kn->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 */ |
| kn = target; |
| while (kn->parent && kn != base) { |
| int slen = strlen(kn->name); |
| |
| len -= slen; |
| memcpy(s + len, kn->name, slen); |
| if (len) |
| s[--len] = '/'; |
| |
| kn = kn->parent; |
| } |
| |
| return 0; |
| } |
| |
| static int kernfs_getlink(struct inode *inode, char *path) |
| { |
| struct kernfs_node *kn = inode->i_private; |
| struct kernfs_node *parent = kn->parent; |
| struct kernfs_node *target = kn->symlink.target_kn; |
| int error; |
| |
| mutex_lock(&kernfs_mutex); |
| error = kernfs_get_target_path(parent, target, path); |
| mutex_unlock(&kernfs_mutex); |
| |
| return error; |
| } |
| |
| static const char *kernfs_iop_get_link(struct dentry *dentry, |
| struct inode *inode, |
| struct delayed_call *done) |
| { |
| char *body; |
| int error; |
| |
| if (!dentry) |
| return ERR_PTR(-ECHILD); |
| body = kzalloc(PAGE_SIZE, GFP_KERNEL); |
| if (!body) |
| return ERR_PTR(-ENOMEM); |
| error = kernfs_getlink(inode, body); |
| if (unlikely(error < 0)) { |
| kfree(body); |
| return ERR_PTR(error); |
| } |
| set_delayed_call(done, kfree_link, body); |
| return body; |
| } |
| |
| const struct inode_operations kernfs_symlink_iops = { |
| .listxattr = kernfs_iop_listxattr, |
| .get_link = kernfs_iop_get_link, |
| .setattr = kernfs_iop_setattr, |
| .getattr = kernfs_iop_getattr, |
| .permission = kernfs_iop_permission, |
| }; |