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
  18static 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 */
  33static 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 */
  53struct 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
  69void 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}
  76