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/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2024 Arm Ltd
*
* 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.
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*/
/*
* A driver for the Arm True Random Number Generator Firmware Interface.
* This queries into the SMCCC firmware for random numbers using the
* interface documented in den0098 [1].
*
* [1] https://developer.arm.com/documentation/den0098/latest
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/random.h>
#include <dev/psci/psci.h>
#include <dev/psci/smccc.h>
#include <dev/random/randomdev.h>
#define TRNG_VERSION SMCCC_FUNC_ID(SMCCC_FAST_CALL, \
SMCCC_32BIT_CALL, SMCCC_STD_SECURE_SERVICE_CALLS, 0x50)
#define TRNG_VERSION_MIN 0x10000L
#define TRNG_RND64 SMCCC_FUNC_ID(SMCCC_FAST_CALL, \
SMCCC_64BIT_CALL, SMCCC_STD_SECURE_SERVICE_CALLS, 0x53)
static device_identify_t trng_identify;
static device_probe_t trng_probe;
static device_attach_t trng_attach;
static unsigned trng_read(void *, unsigned);
static const struct random_source random_trng = {
.rs_ident = "Arm SMCCC TRNG",
.rs_source = RANDOM_PURE_ARM_TRNG,
.rs_read = trng_read,
};
static void
trng_identify(driver_t *driver, device_t parent)
{
int32_t version;
/* Check if TRNG is supported */
if (smccc_arch_features(TRNG_VERSION) != SMCCC_RET_SUCCESS)
return;
/* Check we have TRNG 1.0 or later */
version = psci_call(TRNG_VERSION, 0, 0, 0);
if (version < TRNG_VERSION_MIN)
return;
if (BUS_ADD_CHILD(parent, 0, "trng", DEVICE_UNIT_ANY) == NULL)
device_printf(parent, "add TRNG child failed\n");
}
static int
trng_probe(device_t dev)
{
device_set_desc(dev, "Arm SMCCC TRNG");
return (BUS_PROBE_NOWILDCARD);
}
static int
trng_attach(device_t dev)
{
struct arm_smccc_res res;
int32_t ret;
ret = arm_smccc_invoke(TRNG_RND64, 192, &res);
if (ret < 0) {
device_printf(dev, "Failed to read fron TRNG\n");
} else {
random_source_register(&random_trng);
}
return (0);
}
static unsigned
trng_read(void *buf, unsigned usz)
{
struct arm_smccc_res res;
register_t len;
int32_t ret;
len = usz;
if (len > sizeof(uint64_t))
len = sizeof(uint64_t);
if (len == 0)
return (0);
ret = arm_smccc_invoke(TRNG_RND64, len * 8, &res);
if (ret < 0)
return (0);
memcpy(buf, &res.a3, len);
return (len);
}
static device_method_t trng_methods[] = {
DEVMETHOD(device_identify, trng_identify),
DEVMETHOD(device_probe, trng_probe),
DEVMETHOD(device_attach, trng_attach),
DEVMETHOD_END
};
static driver_t trng_driver = {
"trng",
trng_methods,
0
};
DRIVER_MODULE(trng, smccc, trng_driver, 0, 0);
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