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 #include <linux/slab.h>
  18
  19 /*
  20  * Clone a new ns copying an original utsname, setting refcount to 1
  21  * @old_ns: namespace to clone
  22  * Return NULL on error (failure to kmalloc), new ns otherwise
  23  */
  24 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  25 {
  26         struct uts_namespace *ns;
  27
  28         ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  29         if (!ns)
  30                 return ERR_PTR(-ENOMEM);
  31
  32         down_read(&uts_sem);
  33         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  34         up_read(&uts_sem);
  35         kref_init(&ns->kref);
  36         return ns;
  37 }
  38
  39 /*
  40  * Copy task tsk's utsname namespace, or clone it if flags
  41  * specifies CLONE_NEWUTS.  In latter case, changes to the
  42  * utsname of this process won't be seen by parent, and vice
  43  * versa.
  44  */
  45 struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)
  46 {
  47         struct uts_namespace *new_ns;
  48
  49         BUG_ON(!old_ns);
  50         get_uts_ns(old_ns);
  51
  52         if (!(flags & CLONE_NEWUTS))
  53                 return old_ns;
  54
  55         new_ns = clone_uts_ns(old_ns);
  56
  57         put_uts_ns(old_ns);
  58         return new_ns;
  59 }
  60
  61 void free_uts_ns(struct kref *kref)
  62 {
  63         struct uts_namespace *ns;
  64
  65         ns = container_of(kref, struct uts_namespace, kref);
  66         kfree(ns);
  67 }