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/sysctl.h>
  16
  17 static void *get_uts(ctl_table *table, int write)
  18 {
  19         char *which = table->data;
  20         struct uts_namespace *uts_ns;
  21
  22         uts_ns = current->nsproxy->uts_ns;
  23         which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
  24
  25         if (!write)
  26                 down_read(&uts_sem);
  27         else
  28                 down_write(&uts_sem);
  29         return which;
  30 }
  31
  32 static void put_uts(ctl_table *table, int write, void *which)
  33 {
  34         if (!write)
  35                 up_read(&uts_sem);
  36         else
  37                 up_write(&uts_sem);
  38 }
  39
  40 #ifdef CONFIG_PROC_SYSCTL
  41 /*
  42  *      Special case of dostring for the UTS structure. This has locks
  43  *      to observe. Should this be in kernel/sys.c ????
  44  */
  45 static int proc_do_uts_string(ctl_table *table, int write,
  46                   void __user *buffer, size_t *lenp, loff_t *ppos)
  47 {
  48         struct ctl_table uts_table;
  49         int r;
  50         memcpy(&uts_table, table, sizeof(uts_table));
  51         uts_table.data = get_uts(table, write);
  52         r = proc_dostring(&uts_table,write,buffer,lenp, ppos);
  53         put_uts(table, write, uts_table.data);
  54         return r;
  55 }
  56 #else
  57 #define proc_do_uts_string NULL
  58 #endif
  59
  60
  61 #ifdef CONFIG_SYSCTL_SYSCALL
  62 /* The generic string strategy routine: */
  63 static int sysctl_uts_string(ctl_table *table,
  64                   void __user *oldval, size_t __user *oldlenp,
  65                   void __user *newval, size_t newlen)
  66 {
  67         struct ctl_table uts_table;
  68         int r, write;
  69         write = newval && newlen;
  70         memcpy(&uts_table, table, sizeof(uts_table));
  71         uts_table.data = get_uts(table, write);
  72         r = sysctl_string(&uts_table, oldval, oldlenp, newval, newlen);
  73         put_uts(table, write, uts_table.data);
  74         return r;
  75 }
  76 #else
  77 #define sysctl_uts_string NULL
  78 #endif
  79
  80 static struct ctl_table uts_kern_table[] = {
  81         {
  82                 .ctl_name       = KERN_OSTYPE,
  83                 .procname       = "ostype",
  84                 .data           = init_uts_ns.name.sysname,
  85                 .maxlen         = sizeof(init_uts_ns.name.sysname),
  86                 .mode           = 0444,
  87                 .proc_handler   = proc_do_uts_string,
  88                 .strategy       = sysctl_uts_string,
  89         },
  90         {
  91                 .ctl_name       = KERN_OSRELEASE,
  92                 .procname       = "osrelease",
  93                 .data           = init_uts_ns.name.release,
  94                 .maxlen         = sizeof(init_uts_ns.name.release),
  95                 .mode           = 0444,
  96                 .proc_handler   = proc_do_uts_string,
  97                 .strategy       = sysctl_uts_string,
  98         },
  99         {
 100                 .ctl_name       = KERN_VERSION,
 101                 .procname       = "version",
 102                 .data           = init_uts_ns.name.version,
 103                 .maxlen         = sizeof(init_uts_ns.name.version),
 104                 .mode           = 0444,
 105                 .proc_handler   = proc_do_uts_string,
 106                 .strategy       = sysctl_uts_string,
 107         },
 108         {
 109                 .ctl_name       = KERN_NODENAME,
 110                 .procname       = "hostname",
 111                 .data           = init_uts_ns.name.nodename,
 112                 .maxlen         = sizeof(init_uts_ns.name.nodename),
 113                 .mode           = 0644,
 114                 .proc_handler   = proc_do_uts_string,
 115                 .strategy       = sysctl_uts_string,
 116         },
 117         {
 118                 .ctl_name       = KERN_DOMAINNAME,
 119                 .procname       = "domainname",
 120                 .data           = init_uts_ns.name.domainname,
 121                 .maxlen         = sizeof(init_uts_ns.name.domainname),
 122                 .mode           = 0644,
 123                 .proc_handler   = proc_do_uts_string,
 124                 .strategy       = sysctl_uts_string,
 125         },
 126         {}
 127 };
 128
 129 static struct ctl_table uts_root_table[] = {
 130         {
 131                 .ctl_name       = CTL_KERN,
 132                 .procname       = "kernel",
 133                 .mode           = 0555,
 134                 .child          = uts_kern_table,
 135         },
 136         {}
 137 };
 138
 139 static int __init utsname_sysctl_init(void)
 140 {
 141         register_sysctl_table(uts_root_table);
 142         return 0;
 143 }
 144
 145 __initcall(utsname_sysctl_init);