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