/*      $OpenBSD: tcb.h,v 1.6 2017/10/13 05:14:02 guenther Exp $        */

/*
 * Copyright (c) 2011 Philip Guenther <guenther@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef _MACHINE_TCB_H_
#define _MACHINE_TCB_H_

#ifdef _KERNEL

void    *tcb_get(struct proc *_p);
void    tcb_set(struct proc *_p, void *_newtcb);

#define TCB_GET(p)              tcb_get(p)
#define TCB_SET(p, addr)        tcb_set(p, addr)

/* address must be in canonical form; requiring lower-half is okay */
#define TCB_INVALID(addr)       ((u_long)(addr) > 0x00007fffffffffff)

#else /* _KERNEL */

/* ELF TLS ABI calls for big TCB, with static TLS data at negative offsets */
#define TLS_VARIANT     2

/* Read a slot from the TCB */
static inline void *
__amd64_read_tcb(long offset)
{
        void    *val;
        __asm__ ("movq %%fs:(%1),%0" : "=r" (val) : "r" (offset));
        return val;
}

/* Get a pointer to the TCB itself */
#define TCB_GET()               __amd64_read_tcb(0)

/* Setting the TCB pointer can only be done via syscall, so no TCB_SET() */

#endif /* _KERNEL */
#endif /* _MACHINE_TCB_H_ */