kernel/utsname.c

   1 /*
   2  *  Copyright (C) 2004 IBM Corporation
   3  *
   4  *  Author: Serge Hallyn <serue@us.ibm.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
  17 /*
  18  * Clone a new ns copying an original utsname, setting refcount to 1
  19  * @old_ns: namespace to clone
  20  * Return NULL on error (failure to kmalloc), new ns otherwise
  21  */
  22 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  23 {
  24         struct uts_namespace *ns;
  25
  26         ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  27         if (ns) {
  28                 memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  29                 kref_init(&ns->kref);
  30         }
  31         return ns;
  32 }
  33
  34 /*
  35  * Copy task tsk's utsname namespace, or clone it if flags
  36  * specifies CLONE_NEWUTS.  In latter case, changes to the
  37  * utsname of this process won't be seen by parent, and vice
  38  * versa.
  39  */
  40 struct uts_namespace *copy_utsname(int flags, struct uts_namespace *old_ns)
  41 {
  42         struct uts_namespace *new_ns;
  43
  44         BUG_ON(!old_ns);
  45         get_uts_ns(old_ns);
  46
  47         if (!(flags & CLONE_NEWUTS))
  48                 return old_ns;
  49
  50         new_ns = clone_uts_ns(old_ns);
  51
  52         put_uts_ns(old_ns);
  53         return new_ns;
  54 }
  55
  56 void free_uts_ns(struct kref *kref)
  57 {
  58         struct uts_namespace *ns;
  59
  60         ns = container_of(kref, struct uts_namespace, kref);
  61         kfree(ns);
  62 }