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/param.h>
35 #include <sys/kernel.h>
36 #include <sys/conf.h>
37 #include <sys/lock.h>
38 #include <sys/malloc.h>
39 #include <sys/module.h>
40 #include <sys/random.h>
41 #include <sys/systm.h>
42
43 #include <machine/cpu.h>
44 #include <machine/md_var.h>
45
46 #include <dev/random/randomdev.h>
47
48 /*
49 * Power ISA 3.0 adds a "darn" instruction (Deliver A Random Number). The RNG
50 * backing this instruction conforms to NIST SP800-90B and SP800-90C at the
51 * point of hardware design, and provides a minimum of 0.5 bits of entropy per
52 * bit.
53 */
54
55 #define RETRY_COUNT 10
56
57 static u_int random_darn_read(void *, u_int);
58
59 static struct random_source random_darn = {
60 .rs_ident = "PowerISA DARN random number generator",
61 .rs_source = RANDOM_PURE_DARN,
62 .rs_read = random_darn_read
63 };
64
65 static inline int
darn_rng_store(u_long * buf)66 darn_rng_store(u_long *buf)
67 {
68 u_long rndval;
69 int retry;
70
71 for (retry = RETRY_COUNT; retry > 0; --retry) {
72 /* "DARN %rN, 1" instruction */
73 /*
74 * Arguments for DARN: rN and "L", where "L" can be one of:
75 * 0 - 32-bit conditional random number
76 * 1 - Conditional random number (conditioned to remove bias)
77 * 2 - Raw random number (unprocessed, may include bias)
78 * 3 - Reserved
79 */
80 __asm __volatile(".long 0x7c0105e6 | (%0 << 21)" :
81 "+r"(rndval));
82 if (rndval != ~0)
83 break;
84 }
85
86 *buf = rndval;
87 return (retry);
88 }
89
90 /* It is required that buf length is a multiple of sizeof(u_long). */
91 static u_int
random_darn_read(void * buf,u_int c)92 random_darn_read(void *buf, u_int c)
93 {
94 u_long *b, rndval;
95 u_int count;
96
97 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
98 b = buf;
99 for (count = c; count > 0; count -= sizeof(*b)) {
100 if (darn_rng_store(&rndval) == 0)
101 break;
102 *b++ = rndval;
103 }
104 return (c - count);
105 }
106
107 static int
darn_modevent(module_t mod,int type,void * unused)108 darn_modevent(module_t mod, int type, void *unused)
109 {
110 int error = 0;
111
112 switch (type) {
113 case MOD_LOAD:
114 if (cpu_features2 & PPC_FEATURE2_DARN) {
115 random_source_register(&random_darn);
116 printf("random: fast provider: \"%s\"\n", random_darn.rs_ident);
117 }
118 break;
119
120 case MOD_UNLOAD:
121 if (cpu_features2 & PPC_FEATURE2_DARN)
122 random_source_deregister(&random_darn);
123 break;
124
125 case MOD_SHUTDOWN:
126 break;
127
128 default:
129 error = EOPNOTSUPP;
130 break;
131
132 }
133
134 return (error);
135 }
136
137 static moduledata_t darn_mod = {
138 "darn",
139 darn_modevent,
140 0
141 };
142
143 DECLARE_MODULE(darn, darn_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
144 MODULE_VERSION(darn, 1);
145 MODULE_DEPEND(darn, random_harvestq, 1, 1, 1);
146