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 /*
  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         down_read(&uts_sem);
  32         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  33         up_read(&uts_sem);
  34         kref_init(&ns->kref);
  35         return ns;
  36 }
  37
  38 /*
  39  * Copy task tsk's utsname namespace, or clone it if flags
  40  * specifies CLONE_NEWUTS.  In latter case, changes to the
  41  * utsname of this process won't be seen by parent, and vice
  42  * versa.
  43  */
  44 struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)
  45 {
  46         struct uts_namespace *new_ns;
  47
  48         BUG_ON(!old_ns);
  49         get_uts_ns(old_ns);
  50
  51         if (!(flags & CLONE_NEWUTS))
  52                 return old_ns;
  53
  54         new_ns = clone_uts_ns(old_ns);
  55
  56         put_uts_ns(old_ns);
  57         return new_ns;
  58 }
  59
  60 void free_uts_ns(struct kref *kref)
  61 {
  62         struct uts_namespace *ns;
  63
  64         ns = container_of(kref, struct uts_namespace, kref);
  65         kfree(ns);
  66 }