1 /*-
2 * Copyright (c) 2018 Justin Hibbits
3 * Copyright (c) 2013 The FreeBSD Foundation
4 * Copyright (c) 2013 David E. O'Brien <[email protected]>
5 * Copyright (c) 2012 Konstantin Belousov <[email protected]>
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 #include <sys/param.h>
36 #include <sys/kernel.h>
37 #include <sys/conf.h>
38 #include <sys/lock.h>
39 #include <sys/malloc.h>
40 #include <sys/module.h>
41 #include <sys/random.h>
42 #include <sys/systm.h>
43
44 #include <machine/cpu.h>
45 #include <machine/md_var.h>
46
47 #include <dev/random/randomdev.h>
48
49 /*
50 * Power ISA 3.0 adds a "darn" instruction (Deliver A Random Number). The RNG
51 * backing this instruction conforms to NIST SP800-90B and SP800-90C at the
52 * point of hardware design, and provides a minimum of 0.5 bits of entropy per
53 * bit.
54 */
55
56 #define RETRY_COUNT 10
57
58 static u_int random_darn_read(void *, u_int);
59
60 static struct random_source random_darn = {
61 .rs_ident = "PowerISA DARN random number generator",
62 .rs_source = RANDOM_PURE_DARN,
63 .rs_read = random_darn_read
64 };
65
66 static inline int
darn_rng_store(u_long * buf)67 darn_rng_store(u_long *buf)
68 {
69 u_long rndval;
70 int retry;
71
72 for (retry = RETRY_COUNT; retry > 0; --retry) {
73 /* "DARN %rN, 1" instruction */
74 /*
75 * Arguments for DARN: rN and "L", where "L" can be one of:
76 * 0 - 32-bit conditional random number
77 * 1 - Conditional random number (conditioned to remove bias)
78 * 2 - Raw random number (unprocessed, may include bias)
79 * 3 - Reserved
80 */
81 __asm __volatile(".long 0x7c0105e6 | (%0 << 21)" :
82 "+r"(rndval));
83 if (rndval != ~0)
84 break;
85 }
86
87 *buf = rndval;
88 return (retry);
89 }
90
91 /* It is required that buf length is a multiple of sizeof(u_long). */
92 static u_int
random_darn_read(void * buf,u_int c)93 random_darn_read(void *buf, u_int c)
94 {
95 u_long *b, rndval;
96 u_int count;
97
98 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
99 b = buf;
100 for (count = c; count > 0; count -= sizeof(*b)) {
101 if (darn_rng_store(&rndval) == 0)
102 break;
103 *b++ = rndval;
104 }
105 return (c - count);
106 }
107
108 static int
darn_modevent(module_t mod,int type,void * unused)109 darn_modevent(module_t mod, int type, void *unused)
110 {
111 int error = 0;
112
113 switch (type) {
114 case MOD_LOAD:
115 if (cpu_features2 & PPC_FEATURE2_DARN) {
116 random_source_register(&random_darn);
117 printf("random: fast provider: \"%s\"\n", random_darn.rs_ident);
118 }
119 break;
120
121 case MOD_UNLOAD:
122 if (cpu_features2 & PPC_FEATURE2_DARN)
123 random_source_deregister(&random_darn);
124 break;
125
126 case MOD_SHUTDOWN:
127 break;
128
129 default:
130 error = EOPNOTSUPP;
131 break;
132
133 }
134
135 return (error);
136 }
137
138 static moduledata_t darn_mod = {
139 "darn",
140 darn_modevent,
141 0
142 };
143
144 DECLARE_MODULE(darn, darn_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
145 MODULE_VERSION(darn, 1);
146 MODULE_DEPEND(darn, random_harvestq, 1, 1, 1);
147