/*-
 * Copyright (c) 2013-2015 Mark R V Murray
 * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
 * 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
 *    in this position and unchanged.
 * 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 AUTHOR ``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 AUTHOR 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/param.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/random.h>
#include <sys/systm.h>

#include <machine/segments.h>
#include <machine/pcb.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>

#include <dev/random/randomdev.h>

static u_int random_nehemiah_read(void *, u_int);

static const struct random_source random_nehemiah = {
        .rs_ident = "VIA Nehemiah Padlock RNG",
        .rs_source = RANDOM_PURE_NEHEMIAH,
        .rs_read = random_nehemiah_read
};

/* This H/W source never stores more than 8 bytes in one go */
/* ARGSUSED */
static __inline size_t
VIA_RNG_store(void *buf)
{
        uint32_t retval = 0;
        uint32_t rate = 0;

        __asm __volatile(
                "movl   $0,%%edx\n\t"
                ".byte 0x0f, 0xa7, 0xc0"
                        : "=a" (retval), "+d" (rate), "+D" (buf)
                        :
                        : "memory"
        );
        if (rate == 0)
                return (retval&0x1f);
        return (0);
}

/* It is specifically allowed that buf is a multiple of sizeof(long) */
static u_int
random_nehemiah_read(void *buf, u_int c)
{
        uint8_t *b;
        size_t count, ret;
        uint64_t tmp;

        fpu_kern_enter(curthread, NULL, FPU_KERN_NORMAL | FPU_KERN_NOCTX);
        b = buf;
        for (count = c; count > 0; count -= ret) {
                ret = MIN(VIA_RNG_store(&tmp), count);
                memcpy(b, &tmp, ret);
                b += ret;
        }
        fpu_kern_leave(curthread, NULL);

        return (c);
}

static int
nehemiah_modevent(module_t mod, int type, void *unused)
{
        int error = 0;

        switch (type) {
        case MOD_LOAD:
                if (via_feature_rng & VIA_HAS_RNG) {
                        random_source_register(&random_nehemiah);
                        printf("random: fast provider: \"%s\"\n", random_nehemiah.rs_ident);
                }
                break;

        case MOD_UNLOAD:
                if (via_feature_rng & VIA_HAS_RNG) {
                        random_source_deregister(&random_nehemiah);
                }
                break;

        case MOD_SHUTDOWN:
                break;

        default:
                error = EOPNOTSUPP;
                break;

        }

        return (error);
}

static moduledata_t nehemiah_mod = {
        "nehemiah",
        nehemiah_modevent,
        0
};

DECLARE_MODULE(nehemiah, nehemiah_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
MODULE_VERSION(nehemiah, 1);
MODULE_DEPEND(nehemiah, random_harvestq, 1, 1, 1);