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/module.h>
  13 #include <linux/uts.h>
  14 #include <linux/utsname.h>
  15 #include <linux/version.h>
  16 #include <linux/sysctl.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_FS
  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, struct file *filp,
  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,filp,buffer,lenp, ppos);
  54         put_uts(table, write, uts_table.data);
  55         return r;
  56 }
  57 #else
  58 #define proc_do_uts_string NULL
  59 #endif
  60
  61
  62 #ifdef CONFIG_SYSCTL_SYSCALL
  63 /* The generic string strategy routine: */
  64 static int sysctl_uts_string(ctl_table *table, int __user *name, int nlen,
  65                   void __user *oldval, size_t __user *oldlenp,
  66                   void __user *newval, size_t newlen)
  67 {
  68         struct ctl_table uts_table;
  69         int r, write;
  70         write = newval && newlen;
  71         memcpy(&uts_table, table, sizeof(uts_table));
  72         uts_table.data = get_uts(table, write);
  73         r = sysctl_string(&uts_table, name, nlen,
  74                 oldval, oldlenp, newval, newlen);
  75         put_uts(table, write, uts_table.data);
  76         return r;
  77 }
  78 #else
  79 #define sysctl_uts_string NULL
  80 #endif
  81
  82 static struct ctl_table uts_kern_table[] = {
  83         {
  84                 .ctl_name       = KERN_OSTYPE,
  85                 .procname       = "ostype",
  86                 .data           = init_uts_ns.name.sysname,
  87                 .maxlen         = sizeof(init_uts_ns.name.sysname),
  88                 .mode           = 0444,
  89                 .proc_handler   = proc_do_uts_string,
  90                 .strategy       = sysctl_uts_string,
  91         },
  92         {
  93                 .ctl_name       = KERN_OSRELEASE,
  94                 .procname       = "osrelease",
  95                 .data           = init_uts_ns.name.release,
  96                 .maxlen         = sizeof(init_uts_ns.name.release),
  97                 .mode           = 0444,
  98                 .proc_handler   = proc_do_uts_string,
  99                 .strategy       = sysctl_uts_string,
 100         },
 101         {
 102                 .ctl_name       = KERN_VERSION,
 103                 .procname       = "version",
 104                 .data           = init_uts_ns.name.version,
 105                 .maxlen         = sizeof(init_uts_ns.name.version),
 106                 .mode           = 0444,
 107                 .proc_handler   = proc_do_uts_string,
 108                 .strategy       = sysctl_uts_string,
 109         },
 110         {
 111                 .ctl_name       = KERN_NODENAME,
 112                 .procname       = "hostname",
 113                 .data           = init_uts_ns.name.nodename,
 114                 .maxlen         = sizeof(init_uts_ns.name.nodename),
 115                 .mode           = 0644,
 116                 .proc_handler   = proc_do_uts_string,
 117                 .strategy       = sysctl_uts_string,
 118         },
 119         {
 120                 .ctl_name       = KERN_DOMAINNAME,
 121                 .procname       = "domainname",
 122                 .data           = init_uts_ns.name.domainname,
 123                 .maxlen         = sizeof(init_uts_ns.name.domainname),
 124                 .mode           = 0644,
 125                 .proc_handler   = proc_do_uts_string,
 126                 .strategy       = sysctl_uts_string,
 127         },
 128         {}
 129 };
 130
 131 static struct ctl_table uts_root_table[] = {
 132         {
 133                 .ctl_name       = CTL_KERN,
 134                 .procname       = "kernel",
 135                 .mode           = 0555,
 136                 .child          = uts_kern_table,
 137         },
 138         {}
 139 };
 140
 141 static int __init utsname_sysctl_init(void)
 142 {
 143         register_sysctl_table(uts_root_table);
 144         return 0;
 145 }
 146
 147 __initcall(utsname_sysctl_init);