1#include <linux/sched.h>
 2#include <linux/slab.h>
 3#include <linux/pid_namespace.h>
 4#include "internal.h"
 5
 6/*
 7 * /proc/self:
 8 */
 9static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
10			      int buflen)
11{
12	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
13	pid_t tgid = task_tgid_nr_ns(current, ns);
14	char tmp[PROC_NUMBUF];
15	if (!tgid)
16		return -ENOENT;
17	sprintf(tmp, "%d", tgid);
18	return readlink_copy(buffer, buflen, tmp);
19}
20
21static const char *proc_self_get_link(struct dentry *dentry,
22				      struct inode *inode,
23				      struct delayed_call *done)
24{
25	struct pid_namespace *ns = inode->i_sb->s_fs_info;
26	pid_t tgid = task_tgid_nr_ns(current, ns);
27	char *name;
28
29	if (!tgid)
30		return ERR_PTR(-ENOENT);
31	/* 11 for max length of signed int in decimal + NULL term */
32	name = kmalloc(12, dentry ? GFP_KERNEL : GFP_ATOMIC);
33	if (unlikely(!name))
34		return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
35	sprintf(name, "%d", tgid);
36	set_delayed_call(done, kfree_link, name);
37	return name;
38}
39
40static const struct inode_operations proc_self_inode_operations = {
41	.readlink	= proc_self_readlink,
42	.get_link	= proc_self_get_link,
43};
44
45static unsigned self_inum;
46
47int proc_setup_self(struct super_block *s)
48{
49	struct inode *root_inode = d_inode(s->s_root);
50	struct pid_namespace *ns = s->s_fs_info;
51	struct dentry *self;
52	
53	inode_lock(root_inode);
54	self = d_alloc_name(s->s_root, "self");
55	if (self) {
56		struct inode *inode = new_inode_pseudo(s);
57		if (inode) {
58			inode->i_ino = self_inum;
59			inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
60			inode->i_mode = S_IFLNK | S_IRWXUGO;
61			inode->i_uid = GLOBAL_ROOT_UID;
62			inode->i_gid = GLOBAL_ROOT_GID;
63			inode->i_op = &proc_self_inode_operations;
64			d_add(self, inode);
65		} else {
66			dput(self);
67			self = ERR_PTR(-ENOMEM);
68		}
69	} else {
70		self = ERR_PTR(-ENOMEM);
71	}
72	inode_unlock(root_inode);
73	if (IS_ERR(self)) {
74		pr_err("proc_fill_super: can't allocate /proc/self\n");
75		return PTR_ERR(self);
76	}
77	ns->proc_self = self;
78	return 0;
79}
80
81void __init proc_self_init(void)
82{
83	proc_alloc_inum(&self_inum);
84}