freebsd/sys/dev/random/ivy.c

/*-
 * Copyright (c) 2013 The FreeBSD Foundation
 * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
 * All rights reserved.
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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/cdefs.h>
__FBSDID("$FreeBSD$");

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

#include <dev/random/randomdev.h>

#define	RETRY_COUNT	10

static u_int random_ivy_read(void *, u_int);

static struct random_source random_ivy = {
	.rs_ident = "Intel Secure Key RNG",
	.rs_source = RANDOM_PURE_RDRAND,
	.rs_read = random_ivy_read
};

static inline int
ivy_rng_store(u_long *buf)
{
#ifdef __GNUCLIKE_ASM
	u_long rndval;
	int retry;

	retry = RETRY_COUNT;
	__asm __volatile(
	    "1:\n\t"
	    "rdrand	%1\n\t"	/* read randomness into rndval */
	    "jc		2f\n\t" /* CF is set on success, exit retry loop */
	    "dec	%0\n\t" /* otherwise, retry-- */
	    "jne	1b\n\t" /* and loop if retries are not exhausted */
	    "2:"
	    : "+r" (retry), "=r" (rndval) : : "cc");
	*buf = rndval;
	return (retry);
#else /* __GNUCLIKE_ASM */
	return (0);
#endif
}

/* It is required that buf length is a multiple of sizeof(u_long). */
static u_int
random_ivy_read(void *buf, u_int c)
{
	u_long *b, rndval;
	u_int count;

	KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
	b = buf;
	for (count = c; count > 0; count -= sizeof(*b)) {
		if (ivy_rng_store(&rndval) == 0)
			break;
		*b++ = rndval;
	}
	return (c - count);
}

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

	switch (type) {
	case MOD_LOAD:
		if (cpu_feature2 & CPUID2_RDRAND) {
			random_source_register(&random_ivy);
			printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident);
		}
		break;

	case MOD_UNLOAD:
		if (cpu_feature2 & CPUID2_RDRAND)
			random_source_deregister(&random_ivy);
		break;

	case MOD_SHUTDOWN:
		break;

	default:
		error = EOPNOTSUPP;
		break;

	}

	return (error);
}

DEV_MODULE(rdrand, rdrand_modevent, NULL);
MODULE_VERSION(rdrand, 1);
MODULE_DEPEND(rdrand, randomdev, 1, 1, 1);