root/kernel/utsname.c

DEFINITIONS

1. clone_uts_ns
2. copy_utsname
3. free_uts_ns

/*
 *  Copyright (C) 2004 IBM Corporation
 *
 *  Author: Serge Hallyn <serue@us.ibm.com>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation, version 2 of the
 *  License.
 */

#include <linux/module.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/err.h>
#include <linux/slab.h>

/*
 * Clone a new ns copying an original utsname, setting refcount to 1
 * @old_ns: namespace to clone
 * Return NULL on error (failure to kmalloc), new ns otherwise
 */
static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
{
        struct uts_namespace *ns;

        ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
        if (!ns)
                return ERR_PTR(-ENOMEM);

        down_read(&uts_sem);
        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
        up_read(&uts_sem);
        kref_init(&ns->kref);
        return ns;
}

/*
 * Copy task tsk's utsname namespace, or clone it if flags
 * specifies CLONE_NEWUTS.  In latter case, changes to the
 * utsname of this process won't be seen by parent, and vice
 * versa.
 */
struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns)
{
        struct uts_namespace *new_ns;

        BUG_ON(!old_ns);
        get_uts_ns(old_ns);

        if (!(flags & CLONE_NEWUTS))
                return old_ns;

        new_ns = clone_uts_ns(old_ns);

        put_uts_ns(old_ns);
        return new_ns;
}

void free_uts_ns(struct kref *kref)
{
        struct uts_namespace *ns;

        ns = container_of(kref, struct uts_namespace, kref);
        kfree(ns);
}