xref: /freebsd/sys/dev/random/nehemiah.c (revision da5432eda807c4b7232d030d5157d5b417ea4f52)
1 /*-
2  * Copyright (c) 2013-2015 Mark R V Murray
3  * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer
11  *    in this position and unchanged.
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 ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  *
27  */
28 
29 #include <sys/cdefs.h>
30 #include <sys/param.h>
31 #include <sys/kernel.h>
32 #include <sys/conf.h>
33 #include <sys/lock.h>
34 #include <sys/malloc.h>
35 #include <sys/module.h>
36 #include <sys/random.h>
37 #include <sys/systm.h>
38 
39 #include <machine/segments.h>
40 #include <machine/pcb.h>
41 #include <machine/md_var.h>
42 #include <machine/specialreg.h>
43 
44 #include <dev/random/randomdev.h>
45 
46 static void random_nehemiah_init(void);
47 static void random_nehemiah_deinit(void);
48 static u_int random_nehemiah_read(void *, u_int);
49 
50 static struct random_source random_nehemiah = {
51 	.rs_ident = "VIA Nehemiah Padlock RNG",
52 	.rs_source = RANDOM_PURE_NEHEMIAH,
53 	.rs_read = random_nehemiah_read
54 };
55 
56 static struct fpu_kern_ctx *fpu_ctx_save;
57 
58 /* This H/W source never stores more than 8 bytes in one go */
59 /* ARGSUSED */
60 static __inline size_t
61 VIA_RNG_store(void *buf)
62 {
63 	uint32_t retval = 0;
64 	uint32_t rate = 0;
65 
66 	__asm __volatile(
67 		"movl	$0,%%edx\n\t"
68 		".byte 0x0f, 0xa7, 0xc0"
69 			: "=a" (retval), "+d" (rate), "+D" (buf)
70 			:
71 			: "memory"
72 	);
73 	if (rate == 0)
74 		return (retval&0x1f);
75 	return (0);
76 }
77 
78 static void
79 random_nehemiah_init(void)
80 {
81 
82 	fpu_ctx_save = fpu_kern_alloc_ctx(FPU_KERN_NORMAL);
83 }
84 
85 static void
86 random_nehemiah_deinit(void)
87 {
88 
89 	fpu_kern_free_ctx(fpu_ctx_save);
90 }
91 
92 /* It is specifically allowed that buf is a multiple of sizeof(long) */
93 static u_int
94 random_nehemiah_read(void *buf, u_int c)
95 {
96 	uint8_t *b;
97 	size_t count, ret;
98 	uint64_t tmp;
99 
100 	fpu_kern_enter(curthread, fpu_ctx_save, FPU_KERN_NORMAL);
101 	b = buf;
102 	for (count = c; count > 0; count -= ret) {
103 		ret = MIN(VIA_RNG_store(&tmp), count);
104 		memcpy(b, &tmp, ret);
105 		b += ret;
106 	}
107 	fpu_kern_leave(curthread, fpu_ctx_save);
108 
109 	return (c);
110 }
111 
112 static int
113 nehemiah_modevent(module_t mod, int type, void *unused)
114 {
115 	int error = 0;
116 
117 	switch (type) {
118 	case MOD_LOAD:
119 		if (via_feature_rng & VIA_HAS_RNG) {
120 			random_source_register(&random_nehemiah);
121 			printf("random: fast provider: \"%s\"\n", random_nehemiah.rs_ident);
122 			random_nehemiah_init();
123 		}
124 		break;
125 
126 	case MOD_UNLOAD:
127 		if (via_feature_rng & VIA_HAS_RNG) {
128 			random_nehemiah_deinit();
129 			random_source_deregister(&random_nehemiah);
130 		}
131 		break;
132 
133 	case MOD_SHUTDOWN:
134 		break;
135 
136 	default:
137 		error = EOPNOTSUPP;
138 		break;
139 
140 	}
141 
142 	return (error);
143 }
144 
145 static moduledata_t nehemiah_mod = {
146 	"nehemiah",
147 	nehemiah_modevent,
148 	0
149 };
150 
151 DECLARE_MODULE(nehemiah, nehemiah_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
152 MODULE_VERSION(nehemiah, 1);
153 MODULE_DEPEND(nehemiah, random_harvestq, 1, 1, 1);
154