Root/kernel/utsname_sysctl.c

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
20static void *get_uts(ctl_table *table, int write)
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    if (!write)
29        down_read(&uts_sem);
30    else
31        down_write(&uts_sem);
32    return which;
33}
34
35static void put_uts(ctl_table *table, int write, void *which)
36{
37    if (!write)
38        up_read(&uts_sem);
39    else
40        up_write(&uts_sem);
41}
42
43/*
44 * Special case of dostring for the UTS structure. This has locks
45 * to observe. Should this be in kernel/sys.c ????
46 */
47static int proc_do_uts_string(ctl_table *table, int write,
48          void __user *buffer, size_t *lenp, loff_t *ppos)
49{
50    struct ctl_table uts_table;
51    int r;
52    memcpy(&uts_table, table, sizeof(uts_table));
53    uts_table.data = get_uts(table, write);
54    r = proc_dostring(&uts_table,write,buffer,lenp, ppos);
55    put_uts(table, write, uts_table.data);
56
57    if (write)
58        proc_sys_poll_notify(table->poll);
59
60    return r;
61}
62#else
63#define proc_do_uts_string NULL
64#endif
65
66static DEFINE_CTL_TABLE_POLL(hostname_poll);
67static DEFINE_CTL_TABLE_POLL(domainname_poll);
68
69static struct ctl_table uts_kern_table[] = {
70    {
71        .procname = "ostype",
72        .data = init_uts_ns.name.sysname,
73        .maxlen = sizeof(init_uts_ns.name.sysname),
74        .mode = 0444,
75        .proc_handler = proc_do_uts_string,
76    },
77    {
78        .procname = "osrelease",
79        .data = init_uts_ns.name.release,
80        .maxlen = sizeof(init_uts_ns.name.release),
81        .mode = 0444,
82        .proc_handler = proc_do_uts_string,
83    },
84    {
85        .procname = "version",
86        .data = init_uts_ns.name.version,
87        .maxlen = sizeof(init_uts_ns.name.version),
88        .mode = 0444,
89        .proc_handler = proc_do_uts_string,
90    },
91    {
92        .procname = "hostname",
93        .data = init_uts_ns.name.nodename,
94        .maxlen = sizeof(init_uts_ns.name.nodename),
95        .mode = 0644,
96        .proc_handler = proc_do_uts_string,
97        .poll = &hostname_poll,
98    },
99    {
100        .procname = "domainname",
101        .data = init_uts_ns.name.domainname,
102        .maxlen = sizeof(init_uts_ns.name.domainname),
103        .mode = 0644,
104        .proc_handler = proc_do_uts_string,
105        .poll = &domainname_poll,
106    },
107    {}
108};
109
110static struct ctl_table uts_root_table[] = {
111    {
112        .procname = "kernel",
113        .mode = 0555,
114        .child = uts_kern_table,
115    },
116    {}
117};
118
119#ifdef CONFIG_PROC_SYSCTL
120/*
121 * Notify userspace about a change in a certain entry of uts_kern_table,
122 * identified by the parameter proc.
123 */
124void uts_proc_notify(enum uts_proc proc)
125{
126    struct ctl_table *table = &uts_kern_table[proc];
127
128    proc_sys_poll_notify(table->poll);
129}
130#endif
131
132static int __init utsname_sysctl_init(void)
133{
134    register_sysctl_table(uts_root_table);
135    return 0;
136}
137
138__initcall(utsname_sysctl_init);
139

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