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 #ifdef CONFIG_PROC_SYSCTL
  19
  20 static void *get_uts(struct 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
  35 static void put_uts(struct 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  */
  47 static int proc_do_uts_string(struct 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
  66 static DEFINE_CTL_TABLE_POLL(hostname_poll);
  67 static DEFINE_CTL_TABLE_POLL(domainname_poll);
  68
  69 static 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
 110 static 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  */
 124 void 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
 132 static int __init utsname_sysctl_init(void)
 133 {
 134         register_sysctl_table(uts_root_table);
 135         return 0;
 136 }
 137
 138 device_initcall(utsname_sysctl_init);