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