LXR linux/kernel/utsname

   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
  21static void *get_uts(struct ctl_table *table)
  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        return which;
  30}
  31
  32/*
  33 *      Special case of dostring for the UTS structure. This has locks
  34 *      to observe. Should this be in kernel/sys.c ????
  35 */
  36static int proc_do_uts_string(struct ctl_table *table, int write,
  37                  void __user *buffer, size_t *lenp, loff_t *ppos)
  38{
  39        struct ctl_table uts_table;
  40        int r;
  41        char tmp_data[__NEW_UTS_LEN + 1];
  42
  43        memcpy(&uts_table, table, sizeof(uts_table));
  44        uts_table.data = tmp_data;
  45
  46        /*
  47         * Buffer the value in tmp_data so that proc_dostring() can be called
  48         * without holding any locks.
  49         * We also need to read the original value in the write==1 case to
  50         * support partial writes.
  51         */
  52        down_read(&uts_sem);
  53        memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
  54        up_read(&uts_sem);
  55        r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
  56
  57        if (write) {
  58                /*
  59                 * Write back the new value.
  60                 * Note that, since we dropped uts_sem, the result can
  61                 * theoretically be incorrect if there are two parallel writes
  62                 * at non-zero offsets to the same sysctl.
  63                 */
  64                down_write(&uts_sem);
  65                memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
  66                up_write(&uts_sem);
  67                proc_sys_poll_notify(table->poll);
  68        }
  69
  70        return r;
  71}
  72#else
  73#define proc_do_uts_string NULL
  74#endif
  75
  76static DEFINE_CTL_TABLE_POLL(hostname_poll);
  77static DEFINE_CTL_TABLE_POLL(domainname_poll);
  78
  79static struct ctl_table uts_kern_table[] = {
  80        {
  81                .procname       = "ostype",
  82                .data           = init_uts_ns.name.sysname,
  83                .maxlen         = sizeof(init_uts_ns.name.sysname),
  84                .mode           = 0444,
  85                .proc_handler   = proc_do_uts_string,
  86        },
  87        {
  88                .procname       = "osrelease",
  89                .data           = init_uts_ns.name.release,
  90                .maxlen         = sizeof(init_uts_ns.name.release),
  91                .mode           = 0444,
  92                .proc_handler   = proc_do_uts_string,
  93        },
  94        {
  95                .procname       = "version",
  96                .data           = init_uts_ns.name.version,
  97                .maxlen         = sizeof(init_uts_ns.name.version),
  98                .mode           = 0444,
  99                .proc_handler   = proc_do_uts_string,
 100        },
 101        {
 102                .procname       = "hostname",
 103                .data           = init_uts_ns.name.nodename,
 104                .maxlen         = sizeof(init_uts_ns.name.nodename),
 105                .mode           = 0644,
 106                .proc_handler   = proc_do_uts_string,
 107                .poll           = &hostname_poll,
 108        },
 109        {
 110                .procname       = "domainname",
 111                .data           = init_uts_ns.name.domainname,
 112                .maxlen         = sizeof(init_uts_ns.name.domainname),
 113                .mode           = 0644,
 114                .proc_handler   = proc_do_uts_string,
 115                .poll           = &domainname_poll,
 116        },
 117        {}
 118};
 119
 120static struct ctl_table uts_root_table[] = {
 121        {
 122                .procname       = "kernel",
 123                .mode           = 0555,
 124                .child          = uts_kern_table,
 125        },
 126        {}
 127};
 128
 129#ifdef CONFIG_PROC_SYSCTL
 130/*
 131 * Notify userspace about a change in a certain entry of uts_kern_table,
 132 * identified by the parameter proc.
 133 */
 134void uts_proc_notify(enum uts_proc proc)
 135{
 136        struct ctl_table *table = &uts_kern_table[proc];
 137
 138        proc_sys_poll_notify(table->poll);
 139}
 140#endif
 141
 142static int __init utsname_sysctl_init(void)
 143{
 144        register_sysctl_table(uts_root_table);
 145        return 0;
 146}
 147
 148device_initcall(utsname_sysctl_init);
 149