1#include <linux/sched.h>
2#include <linux/namei.h>
3#include <linux/slab.h>
4#include <linux/pid_namespace.h>
5#include "internal.h"
6
7/*
8 * /proc/thread_self:
9 */
10static int proc_thread_self_readlink(struct dentry *dentry, char __user *buffer,
11			      int buflen)
12{
13	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
14	pid_t tgid = task_tgid_nr_ns(current, ns);
15	pid_t pid = task_pid_nr_ns(current, ns);
16	char tmp[PROC_NUMBUF + 6 + PROC_NUMBUF];
17	if (!pid)
18		return -ENOENT;
19	sprintf(tmp, "%d/task/%d", tgid, pid);
20	return readlink_copy(buffer, buflen, tmp);
21}
22
23static void *proc_thread_self_follow_link(struct dentry *dentry, struct nameidata *nd)
24{
25	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
26	pid_t tgid = task_tgid_nr_ns(current, ns);
27	pid_t pid = task_pid_nr_ns(current, ns);
28	char *name = ERR_PTR(-ENOENT);
29	if (pid) {
30		name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF, GFP_KERNEL);
31		if (!name)
32			name = ERR_PTR(-ENOMEM);
33		else
34			sprintf(name, "%d/task/%d", tgid, pid);
35	}
36	nd_set_link(nd, name);
37	return NULL;
38}
39
40static const struct inode_operations proc_thread_self_inode_operations = {
41	.readlink	= proc_thread_self_readlink,
42	.follow_link	= proc_thread_self_follow_link,
43	.put_link	= kfree_put_link,
44};
45
46static unsigned thread_self_inum;
47
48int proc_setup_thread_self(struct super_block *s)
49{
50	struct inode *root_inode = d_inode(s->s_root);
51	struct pid_namespace *ns = s->s_fs_info;
52	struct dentry *thread_self;
53
54	mutex_lock(&root_inode->i_mutex);
55	thread_self = d_alloc_name(s->s_root, "thread-self");
56	if (thread_self) {
57		struct inode *inode = new_inode_pseudo(s);
58		if (inode) {
59			inode->i_ino = thread_self_inum;
60			inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
61			inode->i_mode = S_IFLNK | S_IRWXUGO;
62			inode->i_uid = GLOBAL_ROOT_UID;
63			inode->i_gid = GLOBAL_ROOT_GID;
64			inode->i_op = &proc_thread_self_inode_operations;
65			d_add(thread_self, inode);
66		} else {
67			dput(thread_self);
68			thread_self = ERR_PTR(-ENOMEM);
69		}
70	} else {
71		thread_self = ERR_PTR(-ENOMEM);
72	}
73	mutex_unlock(&root_inode->i_mutex);
74	if (IS_ERR(thread_self)) {
75		pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
76		return PTR_ERR(thread_self);
77	}
78	ns->proc_thread_self = thread_self;
79	return 0;
80}
81
82void __init proc_thread_self_init(void)
83{
84	proc_alloc_inum(&thread_self_inum);
85}
86