1/*-
2 * Copyright (c) 2022 The FreeBSD Foundation
3 *
4 * This software was developed by Andrew Turner under sponsorship from
5 * the FreeBSD Foundation.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30
31#include <sys/param.h>
32#include <sys/systm.h>
33#include <sys/conf.h>
34#include <sys/kernel.h>
35#include <sys/lock.h>
36#include <sys/malloc.h>
37#include <sys/module.h>
38#include <sys/random.h>
39
40#include <machine/armreg.h>
41
42#include <dev/random/randomdev.h>
43
44static u_int random_rndr_read(void *, u_int);
45
46static bool has_rndr;
47static struct random_source random_armv8_rndr = {
48	.rs_ident = "Armv8 rndr RNG",
49	.rs_source = RANDOM_PURE_ARMV8,
50	.rs_read = random_rndr_read,
51};
52
53static inline int
54random_rndr_read_one(u_long *buf)
55{
56	u_long val;
57	int loop, ret;
58
59	loop = 10;
60	do {
61		__asm __volatile(
62		    /* Read the random number */
63		    "mrs	%0, " __XSTRING(RNDRRS_REG) "\n"
64		    /* 1 on success, 0 on failure */
65		    "cset	%w1, ne\n"
66		    : "=&r" (val), "=&r"(ret) :: "cc");
67	} while (ret != 0 && --loop > 0);
68
69	if (ret != 0)
70		*buf = val;
71
72	return (ret);
73}
74
75static u_int
76random_rndr_read(void *buf, u_int c)
77{
78	u_long *b;
79	u_int count;
80
81	b = buf;
82	for (count = 0; count < c; count += sizeof(*b)) {
83		if (!random_rndr_read_one(b))
84			break;
85
86		b++;
87	}
88
89	return (count);
90}
91
92static int
93rndr_modevent(module_t mod, int type, void *unused)
94{
95	uint64_t reg;
96	int error = 0;
97
98	switch (type) {
99	case MOD_LOAD:
100		has_rndr = false;
101		if (get_kernel_reg(ID_AA64ISAR0_EL1, &reg) &&
102		    ID_AA64ISAR0_RNDR_VAL(reg) != ID_AA64ISAR0_RNDR_NONE) {
103			has_rndr = true;
104			random_source_register(&random_armv8_rndr);
105			printf("random: fast provider: \"%s\"\n",
106			    random_armv8_rndr.rs_ident);
107		}
108		break;
109
110	case MOD_UNLOAD:
111		if (has_rndr)
112			random_source_deregister(&random_armv8_rndr);
113		break;
114
115	case MOD_SHUTDOWN:
116		break;
117
118	default:
119		error = EOPNOTSUPP;
120		break;
121
122	}
123
124	return (error);
125}
126
127static moduledata_t rndr_mod = {
128	"rndr",
129	rndr_modevent,
130	0
131};
132
133DECLARE_MODULE(rndr, rndr_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
134MODULE_VERSION(rndr, 1);
135MODULE_DEPEND(rndr, random_harvestq, 1, 1, 1);
136