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 #include <linux/err.h>
  17
  18 /*
  19  * Clone a new ns copying an original utsname, setting refcount to 1
  20  * @old_ns: namespace to clone
  21  * Return NULL on error (failure to kmalloc), new ns otherwise
  22  */
  23 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  24 {
  25         struct uts_namespace *ns;
  26
  27         ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  28         if (!ns)
  29                 return ERR_PTR(-ENOMEM);
  30
  31         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  32         kref_init(&ns->kref);
  33         return ns;
  34 }
  35
  36 /*
  37  * Copy task tsk's utsname namespace, or clone it if flags
  38  * specifies CLONE_NEWUTS.  In latter case, changes to the
  39  * utsname of this process won't be seen by parent, and vice
  40  * versa.
  41  */
  42 struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)
  43 {
  44         struct uts_namespace *new_ns;
  45
  46         BUG_ON(!old_ns);
  47         get_uts_ns(old_ns);
  48
  49         if (!(flags & CLONE_NEWUTS))
  50                 return old_ns;
  51
  52         new_ns = clone_uts_ns(old_ns);
  53
  54         put_uts_ns(old_ns);
  55         return new_ns;
  56 }
  57
  58 void free_uts_ns(struct kref *kref)
  59 {
  60         struct uts_namespace *ns;
  61
  62         ns = container_of(kref, struct uts_namespace, kref);
  63         kfree(ns);
  64 }