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// SPDX-License-Identifier: BSD-2-Clause
/*
* Copyright (c) 2014, 2015 Linaro Limited
*/
#include <arm.h>
#include <crypto/crypto.h>
#include <kernel/misc.h>
#include <kernel/tee_time.h>
#include <kernel/time_source.h>
#include <mm/core_mmu.h>
#include <mpa.h>
#include <stdint.h>
#include <tee/tee_cryp_utl.h>
#include <trace.h>
#include <utee_defines.h>
static TEE_Result arm_cntpct_get_sys_time(TEE_Time *time)
{
uint64_t cntpct = read_cntpct();
uint32_t cntfrq = read_cntfrq();
time->seconds = cntpct / cntfrq;
time->millis = (cntpct % cntfrq) / (cntfrq / TEE_TIME_MILLIS_BASE);
return TEE_SUCCESS;
}
static const struct time_source arm_cntpct_time_source = {
.name = "arm cntpct",
.protection_level = 1000,
.get_sys_time = arm_cntpct_get_sys_time,
};
REGISTER_TIME_SOURCE(arm_cntpct_time_source)
/*
* We collect jitter using cntpct in 32- or 64-bit mode that is typically
* clocked at around 1MHz.
*
* The first time we are called, we add low 16 bits of the counter as entropy.
*
* Subsequently, accumulate 2 low bits each time by:
*
* - rotating the accumumlator by 2 bits
* - XORing it in 2-bit chunks with the whole CNTPCT contents
*
* and adding one byte of entropy when we reach 8 rotated bits.
*/
void plat_prng_add_jitter_entropy(enum crypto_rng_src sid, unsigned int *pnum)
{
uint64_t tsc = read_cntpct();
int bytes = 0, n;
static uint8_t first, bits;
static uint16_t acc;
if (!first) {
acc = tsc;
bytes = 2;
first = 1;
} else {
acc = (acc << 2) | ((acc >> 6) & 3);
for (n = 0; n < 64; n += 2)
acc ^= (tsc >> n) & 3;
bits += 2;
if (bits >= 8) {
bits = 0;
bytes = 1;
}
}
if (bytes) {
FMSG("%s: 0x%02X\n", __func__,
(int)acc & ((1 << (bytes * 8)) - 1));
crypto_rng_add_event(sid, pnum, (uint8_t *)&acc, bytes);
}
}
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