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/*-
* Copyright (c) 2013 The FreeBSD Foundation
* Copyright (c) 2013 David E. O'Brien <obrien@NUXI.org>
* Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
* All rights reserved.
*
* Portions of this software were developed by Konstantin Belousov
* under sponsorship from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer
* in this position and unchanged.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/random.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <x86/ifunc.h>
#include <dev/random/randomdev.h>
#define RETRY_COUNT 10
static bool has_rdrand, has_rdseed;
static u_int random_ivy_read(void *, u_int);
static struct random_source random_ivy = {
.rs_ident = "Intel Secure Key RNG",
.rs_source = RANDOM_PURE_RDRAND,
.rs_read = random_ivy_read
};
SYSCTL_NODE(_kern_random, OID_AUTO, rdrand, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"rdrand (ivy) entropy source");
static bool acquire_independent_seed_samples = false;
SYSCTL_BOOL(_kern_random_rdrand, OID_AUTO, rdrand_independent_seed,
CTLFLAG_RWTUN, &acquire_independent_seed_samples, 0,
"If non-zero, use more expensive and slow, but safer, seeded samples "
"where RDSEED is not present.");
static bool
x86_rdrand_store(u_long *buf)
{
u_long rndval, seed_iterations, i;
int retry;
/* Per [1], "§ 5.2.6 Generating Seeds from RDRAND,"
* machines lacking RDSEED will guarantee RDRAND is reseeded every 8kB
* of generated output.
*
* [1]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide#inpage-nav-6-8
*/
if (acquire_independent_seed_samples)
seed_iterations = 8 * 1024 / sizeof(*buf);
else
seed_iterations = 1;
for (i = 0; i < seed_iterations; i++) {
retry = RETRY_COUNT;
__asm __volatile(
"1:\n\t"
"rdrand %1\n\t" /* read randomness into rndval */
"jc 2f\n\t" /* CF is set on success, exit retry loop */
"dec %0\n\t" /* otherwise, retry-- */
"jne 1b\n\t" /* and loop if retries are not exhausted */
"2:"
: "+r" (retry), "=r" (rndval) : : "cc");
if (retry == 0)
return (false);
}
*buf = rndval;
return (true);
}
static bool
x86_rdseed_store(u_long *buf)
{
u_long rndval;
int retry;
retry = RETRY_COUNT;
__asm __volatile(
"1:\n\t"
"rdseed %1\n\t" /* read randomness into rndval */
"jc 2f\n\t" /* CF is set on success, exit retry loop */
"dec %0\n\t" /* otherwise, retry-- */
"jne 1b\n\t" /* and loop if retries are not exhausted */
"2:"
: "+r" (retry), "=r" (rndval) : : "cc");
*buf = rndval;
return (retry != 0);
}
static bool
x86_unimpl_store(u_long *buf __unused)
{
panic("%s called", __func__);
}
DEFINE_IFUNC(static, bool, x86_rng_store, (u_long *buf))
{
has_rdrand = (cpu_feature2 & CPUID2_RDRAND);
has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED);
if (has_rdseed)
return (x86_rdseed_store);
else if (has_rdrand)
return (x86_rdrand_store);
else
return (x86_unimpl_store);
}
/* It is required that buf length is a multiple of sizeof(u_long). */
static u_int
random_ivy_read(void *buf, u_int c)
{
u_long *b, rndval;
u_int count;
KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
b = buf;
for (count = c; count > 0; count -= sizeof(*b)) {
if (!x86_rng_store(&rndval))
break;
*b++ = rndval;
}
return (c - count);
}
static int
rdrand_modevent(module_t mod, int type, void *unused)
{
int error = 0;
switch (type) {
case MOD_LOAD:
if (has_rdrand || has_rdseed) {
random_source_register(&random_ivy);
printf("random: fast provider: \"%s\"\n", random_ivy.rs_ident);
}
break;
case MOD_UNLOAD:
if (has_rdrand || has_rdseed)
random_source_deregister(&random_ivy);
break;
case MOD_SHUTDOWN:
break;
default:
error = EOPNOTSUPP;
break;
}
return (error);
}
static moduledata_t rdrand_mod = {
"rdrand",
rdrand_modevent,
0
};
DECLARE_MODULE(rdrand, rdrand_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
MODULE_VERSION(rdrand, 1);
MODULE_DEPEND(rdrand, random_harvestq, 1, 1, 1);
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