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
18static void *get_uts(ctl_table *table, int write)
19{
20    char *which = table->data;
21    struct uts_namespace *uts_ns;
22
23    uts_ns = current->nsproxy->uts_ns;
24    which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
25
26    if (!write)
27        down_read(&uts_sem);
28    else
29        down_write(&uts_sem);
30    return which;
31}
32
33static void put_uts(ctl_table *table, int write, void *which)
34{
35    if (!write)
36        up_read(&uts_sem);
37    else
38        up_write(&uts_sem);
39}
40
41#ifdef CONFIG_PROC_SYSCTL
42/*
43 * Special case of dostring for the UTS structure. This has locks
44 * to observe. Should this be in kernel/sys.c ????
45 */
46static int proc_do_uts_string(ctl_table *table, int write,
47          void __user *buffer, size_t *lenp, loff_t *ppos)
48{
49    struct ctl_table uts_table;
50    int r;
51    memcpy(&uts_table, table, sizeof(uts_table));
52    uts_table.data = get_uts(table, write);
53    r = proc_dostring(&uts_table,write,buffer,lenp, ppos);
54    put_uts(table, write, uts_table.data);
55
56    if (write)
57        proc_sys_poll_notify(table->poll);
58
59    return r;
60}
61#else
62#define proc_do_uts_string NULL
63#endif
64
65static DEFINE_CTL_TABLE_POLL(hostname_poll);
66static DEFINE_CTL_TABLE_POLL(domainname_poll);
67
68static struct ctl_table uts_kern_table[] = {
69    {
70        .procname = "ostype",
71        .data = init_uts_ns.name.sysname,
72        .maxlen = sizeof(init_uts_ns.name.sysname),
73        .mode = 0444,
74        .proc_handler = proc_do_uts_string,
75    },
76    {
77        .procname = "osrelease",
78        .data = init_uts_ns.name.release,
79        .maxlen = sizeof(init_uts_ns.name.release),
80        .mode = 0444,
81        .proc_handler = proc_do_uts_string,
82    },
83    {
84        .procname = "version",
85        .data = init_uts_ns.name.version,
86        .maxlen = sizeof(init_uts_ns.name.version),
87        .mode = 0444,
88        .proc_handler = proc_do_uts_string,
89    },
90    {
91        .procname = "hostname",
92        .data = init_uts_ns.name.nodename,
93        .maxlen = sizeof(init_uts_ns.name.nodename),
94        .mode = 0644,
95        .proc_handler = proc_do_uts_string,
96        .poll = &hostname_poll,
97    },
98    {
99        .procname = "domainname",
100        .data = init_uts_ns.name.domainname,
101        .maxlen = sizeof(init_uts_ns.name.domainname),
102        .mode = 0644,
103        .proc_handler = proc_do_uts_string,
104        .poll = &domainname_poll,
105    },
106    {}
107};
108
109static struct ctl_table uts_root_table[] = {
110    {
111        .procname = "kernel",
112        .mode = 0555,
113        .child = uts_kern_table,
114    },
115    {}
116};
117
118#ifdef CONFIG_PROC_SYSCTL
119/*
120 * Notify userspace about a change in a certain entry of uts_kern_table,
121 * identified by the parameter proc.
122 */
123void uts_proc_notify(enum uts_proc proc)
124{
125    struct ctl_table *table = &uts_kern_table[proc];
126
127    proc_sys_poll_notify(table->poll);
128}
129#endif
130
131static int __init utsname_sysctl_init(void)
132{
133    register_sysctl_table(uts_root_table);
134    return 0;
135}
136
137__initcall(utsname_sysctl_init);
138

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