LXR linux/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 */
  23static 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 */
  44struct 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
  60void 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}
  67