1/*-
2 * Copyright (c) 2018 Justin Hibbits
3 * Copyright (c) 2013 The FreeBSD Foundation
4 * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
5 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
6 * All rights reserved.
7 *
8 * Portions of this software were developed by Konstantin Belousov
9 * under sponsorship from the FreeBSD Foundation.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer
16 *    in this position and unchanged.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 *
32 */
33
34#include <sys/cdefs.h>
35__FBSDID("$FreeBSD$");
36
37#include <sys/param.h>
38#include <sys/kernel.h>
39#include <sys/conf.h>
40#include <sys/lock.h>
41#include <sys/malloc.h>
42#include <sys/module.h>
43#include <sys/random.h>
44#include <sys/systm.h>
45
46#include <machine/cpu.h>
47#include <machine/md_var.h>
48
49#include <dev/random/randomdev.h>
50
51/*
52 * Power ISA 3.0 adds a "darn" instruction (Deliver A Random Number).  The RNG
53 * backing this instruction conforms to NIST SP800-90B and SP800-90C at the
54 * point of hardware design, and provides a minimum of 0.5 bits of entropy per
55 * bit.
56 */
57
58#define	RETRY_COUNT	10
59
60static u_int random_darn_read(void *, u_int);
61
62static struct random_source random_darn = {
63	.rs_ident = "PowerISA DARN random number generator",
64	.rs_source = RANDOM_PURE_DARN,
65	.rs_read = random_darn_read
66};
67
68static inline int
69darn_rng_store(u_long *buf)
70{
71	u_long rndval;
72	int retry;
73
74	for (retry = RETRY_COUNT; retry > 0; --retry) {
75		/* "DARN %rN, 1" instruction */
76		/*
77		 * Arguments for DARN: rN and "L", where "L" can be one of:
78		 * 0 - 32-bit conditional random number
79		 * 1 - Conditional random number (conditioned to remove bias)
80		 * 2 - Raw random number	 (unprocessed, may include bias)
81		 * 3 - Reserved
82		 */
83	    	__asm __volatile(".long 0x7c0105e6 | (%0 << 21)" :
84	    	    "+r"(rndval));
85		if (rndval != ~0)
86			break;
87	}
88
89	*buf = rndval;
90	return (retry);
91}
92
93/* It is required that buf length is a multiple of sizeof(u_long). */
94static u_int
95random_darn_read(void *buf, u_int c)
96{
97	u_long *b, rndval;
98	u_int count;
99
100	KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
101	b = buf;
102	for (count = c; count > 0; count -= sizeof(*b)) {
103		if (darn_rng_store(&rndval) == 0)
104			break;
105		*b++ = rndval;
106	}
107	return (c - count);
108}
109
110static int
111darn_modevent(module_t mod, int type, void *unused)
112{
113	int error = 0;
114
115	switch (type) {
116	case MOD_LOAD:
117		if (cpu_features2 & PPC_FEATURE2_DARN) {
118			random_source_register(&random_darn);
119			printf("random: fast provider: \"%s\"\n", random_darn.rs_ident);
120		}
121		break;
122
123	case MOD_UNLOAD:
124		if (cpu_features2 & PPC_FEATURE2_DARN)
125			random_source_deregister(&random_darn);
126		break;
127
128	case MOD_SHUTDOWN:
129		break;
130
131	default:
132		error = EOPNOTSUPP;
133		break;
134
135	}
136
137	return (error);
138}
139
140DEV_MODULE(darn, darn_modevent, NULL);
141MODULE_VERSION(darn, 1);
142MODULE_DEPEND(darn, random_device, 1, 1, 1);
143