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 static 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
  33 static 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  */
  46 static 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
  65 static DEFINE_CTL_TABLE_POLL(hostname_poll);
  66 static DEFINE_CTL_TABLE_POLL(domainname_poll);
  67
  68 static 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
 109 static 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  */
 123 void 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
 131 static int __init utsname_sysctl_init(void)
 132 {
 133         register_sysctl_table(uts_root_table);
 134         return 0;
 135 }
 136
 137 __initcall(utsname_sysctl_init);