1/*-
2 * Copyright (c) 2013 The FreeBSD Foundation
3 * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Portions of this software were developed by Konstantin Belousov
8 * under sponsorship from the FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer
15 *    in this position and unchanged.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 *
31 */
32
33#include <sys/cdefs.h>
34__FBSDID("$FreeBSD$");
35
36#include <sys/param.h>
37#include <sys/kernel.h>
38#include <sys/conf.h>
39#include <sys/lock.h>
40#include <sys/malloc.h>
41#include <sys/module.h>
42#include <sys/random.h>
43#include <sys/systm.h>
44
45#include <machine/md_var.h>
46#include <machine/specialreg.h>
47
48#include <dev/random/randomdev.h>
49
50#define	RETRY_COUNT	10
51
52static u_int random_ivy_read(void *, u_int);
53
54static struct random_source random_ivy = {
55	.rs_ident = "Intel Secure Key RNG",
56	.rs_source = RANDOM_PURE_RDRAND,
57	.rs_read = random_ivy_read
58};
59
60static inline int
61ivy_rng_store(u_long *buf)
62{
63#ifdef __GNUCLIKE_ASM
64	u_long rndval;
65	int retry;
66
67	retry = RETRY_COUNT;
68	__asm __volatile(
69	    "1:\n\t"
70	    "rdrand	%1\n\t"	/* read randomness into rndval */
71	    "jc		2f\n\t" /* CF is set on success, exit retry loop */
72	    "dec	%0\n\t" /* otherwise, retry-- */
73	    "jne	1b\n\t" /* and loop if retries are not exhausted */
74	    "2:"
75	    : "+r" (retry), "=r" (rndval) : : "cc");
76	*buf = rndval;
77	return (retry);
78#else /* __GNUCLIKE_ASM */
79	return (0);
80#endif
81}
82
83/* It is required that buf length is a multiple of sizeof(u_long). */
84static u_int
85random_ivy_read(void *buf, u_int c)
86{
87	u_long *b, rndval;
88	u_int count;
89
90	KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
91	b = buf;
92	for (count = c; count > 0; count -= sizeof(*b)) {
93		if (ivy_rng_store(&rndval) == 0)
94			break;
95		*b++ = rndval;
96	}
97	return (c - count);
98}
99
100static int
101rdrand_modevent(module_t mod, int type, void *unused)
102{
103	int error = 0;
104
105	switch (type) {
106	case MOD_LOAD:
107		if (cpu_feature2 & CPUID2_RDRAND) {
108			random_source_register(&random_ivy);
109			printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident);
110		}
111		break;
112
113	case MOD_UNLOAD:
114		if (cpu_feature2 & CPUID2_RDRAND)
115			random_source_deregister(&random_ivy);
116		break;
117
118	case MOD_SHUTDOWN:
119		break;
120
121	default:
122		error = EOPNOTSUPP;
123		break;
124
125	}
126
127	return (error);
128}
129
130DEV_MODULE(rdrand, rdrand_modevent, NULL);
131MODULE_VERSION(rdrand, 1);
132MODULE_DEPEND(rdrand, random_device, 1, 1, 1);
133