linux/kernel/utsname_sysctl.c
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   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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