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