/*      $NetBSD: kern_ssp.c,v 1.7 2016/12/06 02:55:42 christos Exp $    */

/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_ssp.c,v 1.7 2016/12/06 02:55:42 christos Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/intr.h>
#include <sys/cprng.h>

#if defined(__SSP__) || defined(__SSP_ALL__)
# ifdef _RUMPKERNEL
__weak_alias(__stack_chk_guard, stack_chk_guard)
__weak_alias(__stack_chk_fail, stack_chk_fail)
# define SSP_STATIC static __used
# else
# define stack_chk_guard __stack_chk_guard
# define stack_chk_fail __stack_chk_fail
# define SSP_STATIC
#endif

SSP_STATIC long stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0,};
SSP_STATIC void stack_chk_fail(void);

SSP_STATIC void
stack_chk_fail(void)
{
       panic("stack overflow detected; terminated");
}

void
ssp_init(void)
{
       int s;

       aprint_debug("Initializing SSP: ");
       /*
        * We initialize ssp here carefully:
        *      1. after we got some entropy
        *      2. without calling a function
        */
       size_t i;
       long guard[__arraycount(stack_chk_guard)];

       cprng_fast(guard, sizeof(guard));
       s = splhigh();
       for (i = 0; i < __arraycount(guard); i++)
               stack_chk_guard[i] = guard[i];
       splx(s);
       for (i = 0; i < __arraycount(guard); i++)
               aprint_debug("%lx ", guard[i]);
       aprint_debug("\n");
}
#else
void
ssp_init(void)
{
}
#endif