Root/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

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