path: root/kernel/utsname_sysctl.c (plain)
blob: d2b3b2973456e82a91635f718f98e41157b510ee

1	/*
2	* Copyright (C) 2007
3	*
4	* Author: Eric Biederman <ebiederm@xmision.com>
5	*
6	* This program is free software; you can redistribute it and/or
7	* modify it under the terms of the GNU General Public License as
8	* published by the Free Software Foundation, version 2 of the
9	* License.
10	*/
11
12	#include <linux/export.h>
13	#include <linux/uts.h>
14	#include <linux/utsname.h>
15	#include <linux/sysctl.h>
16	#include <linux/wait.h>
17
18	#ifdef CONFIG_PROC_SYSCTL
19
20	static void *get_uts(struct ctl_table *table)
21	{
22	char *which = table->data;
23	struct uts_namespace *uts_ns;
24
25	uts_ns = current->nsproxy->uts_ns;
26	which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
27
28	return which;
29	}
30
31	/*
32	* Special case of dostring for the UTS structure. This has locks
33	* to observe. Should this be in kernel/sys.c ????
34	*/
35	static int proc_do_uts_string(struct ctl_table *table, int write,
36	void __user *buffer, size_t *lenp, loff_t *ppos)
37	{
38	struct ctl_table uts_table;
39	int r;
40	char tmp_data[__NEW_UTS_LEN + 1];
41
42	memcpy(&uts_table, table, sizeof(uts_table));
43	uts_table.data = tmp_data;
44
45	/*
46	* Buffer the value in tmp_data so that proc_dostring() can be called
47	* without holding any locks.
48	* We also need to read the original value in the write==1 case to
49	* support partial writes.
50	*/
51	down_read(&uts_sem);
52	memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
53	up_read(&uts_sem);
54	r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
55
56	if (write) {
57	/*
58	* Write back the new value.
59	* Note that, since we dropped uts_sem, the result can
60	* theoretically be incorrect if there are two parallel writes
61	* at non-zero offsets to the same sysctl.
62	*/
63	down_write(&uts_sem);
64	memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
65	up_write(&uts_sem);
66	proc_sys_poll_notify(table->poll);
67	}
68
69	return r;
70	}
71	#else
72	#define proc_do_uts_string NULL
73	#endif
74
75	static DEFINE_CTL_TABLE_POLL(hostname_poll);
76	static DEFINE_CTL_TABLE_POLL(domainname_poll);
77
78	static struct ctl_table uts_kern_table[] = {
79	{
80	.procname = "ostype",
81	.data = init_uts_ns.name.sysname,
82	.maxlen = sizeof(init_uts_ns.name.sysname),
83	.mode = 0444,
84	.proc_handler = proc_do_uts_string,
85	},
86	{
87	.procname = "osrelease",
88	.data = init_uts_ns.name.release,
89	.maxlen = sizeof(init_uts_ns.name.release),
90	.mode = 0444,
91	.proc_handler = proc_do_uts_string,
92	},
93	{
94	.procname = "version",
95	.data = init_uts_ns.name.version,
96	.maxlen = sizeof(init_uts_ns.name.version),
97	.mode = 0444,
98	.proc_handler = proc_do_uts_string,
99	},
100	{
101	.procname = "hostname",
102	.data = init_uts_ns.name.nodename,
103	.maxlen = sizeof(init_uts_ns.name.nodename),
104	.mode = 0644,
105	.proc_handler = proc_do_uts_string,
106	.poll = &hostname_poll,
107	},
108	{
109	.procname = "domainname",
110	.data = init_uts_ns.name.domainname,
111	.maxlen = sizeof(init_uts_ns.name.domainname),
112	.mode = 0644,
113	.proc_handler = proc_do_uts_string,
114	.poll = &domainname_poll,
115	},
116	{}
117	};
118
119	static struct ctl_table uts_root_table[] = {
120	{
121	.procname = "kernel",
122	.mode = 0555,
123	.child = uts_kern_table,
124	},
125	{}
126	};
127
128	#ifdef CONFIG_PROC_SYSCTL
129	/*
130	* Notify userspace about a change in a certain entry of uts_kern_table,
131	* identified by the parameter proc.
132	*/
133	void uts_proc_notify(enum uts_proc proc)
134	{
135	struct ctl_table *table = &uts_kern_table[proc];
136
137	proc_sys_poll_notify(table->poll);
138	}
139	#endif
140
141	static int __init utsname_sysctl_init(void)
142	{
143	register_sysctl_table(uts_root_table);
144	return 0;
145	}
146
147	device_initcall(utsname_sysctl_init);
148