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
  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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