root/include/linux/user_namespace.h

INCLUDED FROM

DEFINITIONS

1. get_user_ns
2. put_user_ns
3. get_user_ns
4. copy_user_ns
5. put_user_ns

#ifndef _LINUX_USER_NAMESPACE_H
#define _LINUX_USER_NAMESPACE_H

#include <linux/kref.h>
#include <linux/nsproxy.h>
#include <linux/sched.h>
#include <linux/err.h>

#define UIDHASH_BITS    (CONFIG_BASE_SMALL ? 3 : 8)
#define UIDHASH_SZ      (1 << UIDHASH_BITS)

struct user_namespace {
        struct kref             kref;
        struct hlist_head       uidhash_table[UIDHASH_SZ];
        struct user_struct      *root_user;
};

extern struct user_namespace init_user_ns;

#ifdef CONFIG_USER_NS

static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
{
        if (ns)
                kref_get(&ns->kref);
        return ns;
}

extern struct user_namespace *copy_user_ns(int flags,
                                           struct user_namespace *old_ns);
extern void free_user_ns(struct kref *kref);

static inline void put_user_ns(struct user_namespace *ns)
{
        if (ns)
                kref_put(&ns->kref, free_user_ns);
}

#else

static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
{
        return &init_user_ns;
}

static inline struct user_namespace *copy_user_ns(int flags,
                                                  struct user_namespace *old_ns)
{
        if (flags & CLONE_NEWUSER)
                return ERR_PTR(-EINVAL);

        return old_ns;
}

static inline void put_user_ns(struct user_namespace *ns)
{
}

#endif

#endif /* _LINUX_USER_H */