xref: /freebsd/sys/dev/random/armv8rng.c (revision 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c)
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 
44 static u_int random_rndr_read(void *, u_int);
45 
46 static bool has_rndr;
47 static 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 
53 static inline int
54 random_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 
75 static u_int
76 random_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 
92 static int
93 rndr_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 
127 static moduledata_t rndr_mod = {
128 	"rndr",
129 	rndr_modevent,
130 	0
131 };
132 
133 DECLARE_MODULE(rndr, rndr_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
134 MODULE_VERSION(rndr, 1);
135 MODULE_DEPEND(rndr, random_harvestq, 1, 1, 1);
136