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+/*
+ * Copyright (c) 2014, 2015 Linaro Limited
+ * All rights reserved.
+ *
+ * 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 COPYRIGHT HOLDERS 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 COPYRIGHT HOLDER 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.
+ */
+
+#include <kernel/misc.h>
+#include <kernel/tee_time.h>
+#include <trace.h>
+#include <kernel/time_source.h>
+#include <mm/core_mmu.h>
+#include <utee_defines.h>
+
+#include <tee/tee_cryp_utl.h>
+
+#include <stdint.h>
+#include <mpa.h>
+#include <arm.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(void)
+{
+ 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) {
+ DMSG("%s: 0x%02X\n", __func__,
+ (int)acc & ((1 << (bytes * 8)) - 1));
+ tee_prng_add_entropy((uint8_t *)&acc, bytes);
+ }
+}