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/err.h>
  16 #include <linux/slab.h>
  17
  18 static struct uts_namespace *create_uts_ns(void)
  19 {
  20         struct uts_namespace *uts_ns;
  21
  22         uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  23         if (uts_ns)
  24                 kref_init(&uts_ns->kref);
  25         return uts_ns;
  26 }
  27
  28 /*
  29  * Clone a new ns copying an original utsname, setting refcount to 1
  30  * @old_ns: namespace to clone
  31  * Return NULL on error (failure to kmalloc), new ns otherwise
  32  */
  33 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  34 {
  35         struct uts_namespace *ns;
  36
  37         ns = create_uts_ns();
  38         if (!ns)
  39                 return ERR_PTR(-ENOMEM);
  40
  41         down_read(&uts_sem);
  42         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  43         up_read(&uts_sem);
  44         return ns;
  45 }
  46
  47 /*
  48  * Copy task tsk's utsname namespace, or clone it if flags
  49  * specifies CLONE_NEWUTS.  In latter case, changes to the
  50  * utsname of this process won't be seen by parent, and vice
  51  * versa.
  52  */
  53 struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)
  54 {
  55         struct uts_namespace *new_ns;
  56
  57         BUG_ON(!old_ns);
  58         get_uts_ns(old_ns);
  59
  60         if (!(flags & CLONE_NEWUTS))
  61                 return old_ns;
  62
  63         new_ns = clone_uts_ns(old_ns);
  64
  65         put_uts_ns(old_ns);
  66         return new_ns;
  67 }
  68
  69 void free_uts_ns(struct kref *kref)
  70 {
  71         struct uts_namespace *ns;
  72
  73         ns = container_of(kref, struct uts_namespace, kref);
  74         kfree(ns);
  75 }