1 /*- 2 * Copyright (c) 2013, 2025, David E. O'Brien <deo@NUXI.org> 3 * Copyright (c) 2013 The FreeBSD Foundation 4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org> 5 * All rights reserved. 6 * 7 * Portions of this software were developed by Konstantin Belousov 8 * under sponsorship from the FreeBSD Foundation. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer 15 * in this position and unchanged. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 * 31 */ 32 33 #include <sys/param.h> 34 #include <sys/kernel.h> 35 #include <sys/conf.h> 36 #include <sys/lock.h> 37 #include <sys/malloc.h> 38 #include <sys/module.h> 39 #include <sys/random.h> 40 #include <sys/sysctl.h> 41 #include <sys/systm.h> 42 43 #include <machine/md_var.h> 44 #include <machine/specialreg.h> 45 #include <x86/ifunc.h> 46 47 #include <dev/random/randomdev.h> 48 49 #define RETRY_COUNT 10 50 51 static u_int random_ivy_read(void *, u_int); 52 53 static const struct random_source random_ivy = { 54 .rs_ident = "Intel Secure Key RNG", 55 .rs_source = RANDOM_PURE_RDRAND, 56 .rs_read = random_ivy_read 57 }; 58 59 static bool acquire_independent_seed_samples = false; 60 61 static bool 62 x86_rdrand_store(u_long *buf) 63 { 64 u_long rndval, seed_iterations, i; 65 int retry; 66 67 /* Per [1], "§ 5.2.6 Generating Seeds from RDRAND," 68 * machines lacking RDSEED will guarantee RDRAND is reseeded every 8kB 69 * of generated output. 70 * 71 * [1]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide#inpage-nav-6-8 72 */ 73 if (acquire_independent_seed_samples) 74 seed_iterations = 8 * 1024 / sizeof(*buf); 75 else 76 seed_iterations = 1; 77 78 for (i = 0; i < seed_iterations; i++) { 79 retry = RETRY_COUNT; 80 __asm __volatile( 81 "1:\n\t" 82 "rdrand %1\n\t" /* read randomness into rndval */ 83 "jc 2f\n\t" /* CF is set on success, exit retry loop */ 84 "dec %0\n\t" /* otherwise, retry-- */ 85 "jne 1b\n\t" /* and loop if retries are not exhausted */ 86 "2:" 87 : "+r" (retry), "=r" (rndval) : : "cc"); 88 if (retry == 0) 89 return (false); 90 } 91 *buf = rndval; 92 return (true); 93 } 94 95 /* It is required that buf length is a multiple of sizeof(u_long). */ 96 static u_int 97 random_ivy_read(void *buf, u_int c) 98 { 99 u_long *b, rndval; 100 u_int count; 101 102 KASSERT(c % sizeof(*b) == 0, ("partial read %d", c)); 103 b = buf; 104 for (count = c; count > 0; count -= sizeof(*b)) { 105 if (!x86_rdrand_store(&rndval)) 106 break; 107 *b++ = rndval; 108 } 109 return (c - count); 110 } 111 112 static int 113 rdrand_modevent(module_t mod, int type, void *unused) 114 { 115 struct sysctl_ctx_list ctx; 116 struct sysctl_oid *o; 117 bool has_rdrand, has_rdseed; 118 int error = 0; 119 120 has_rdrand = (cpu_feature2 & CPUID2_RDRAND); 121 has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED); 122 123 switch (type) { 124 case MOD_LOAD: 125 if (has_rdrand && !has_rdseed) { 126 sysctl_ctx_init(&ctx); 127 o = SYSCTL_ADD_NODE(&ctx, SYSCTL_STATIC_CHILDREN(_kern_random), 128 OID_AUTO, "rdrand", CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 129 "rdrand (ivy) entropy source"); 130 SYSCTL_ADD_BOOL(&ctx, SYSCTL_CHILDREN(o), OID_AUTO, 131 "rdrand_independent_seed", CTLFLAG_RDTUN, 132 &acquire_independent_seed_samples, 0, 133 "If non-zero, use more expensive and slow, but safer, seeded samples " 134 "where RDSEED is not present."); 135 random_source_register(&random_ivy); 136 printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident); 137 } 138 break; 139 140 case MOD_UNLOAD: 141 if (has_rdrand && !has_rdseed) 142 random_source_deregister(&random_ivy); 143 break; 144 145 case MOD_SHUTDOWN: 146 break; 147 148 default: 149 error = EOPNOTSUPP; 150 break; 151 152 } 153 154 return (error); 155 } 156 157 static moduledata_t rdrand_mod = { 158 "rdrand", 159 rdrand_modevent, 160 0 161 }; 162 163 DECLARE_MODULE(rdrand, rdrand_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH); 164 MODULE_VERSION(rdrand, 1); 165 MODULE_DEPEND(rdrand, random_harvestq, 1, 1, 1); 166