linux-gen: random: implement true random number generation on aarch64

Implement true random data on aarch64 via RNDR register introduced as an
extension in Armv8.5-a ISA.

Signed-off-by: Malvika Gupta <Malvika.Gupta@arm.com>
Reviewed-by: Govindarajan <govindarajan.mohandoss@arm.com>
Reviewed-by: Jere Leppänen <jere.leppanen@nokia.com>
Reviewed-by: Matias Elo <matias.elo@nokia.com>
Reviewed-by: Petri Savolainen <petri.savolainen@nokia.com>

1 files changed, 166 insertions, 0 deletions

diff --git a/platform/linux-generic/arch/aarch64/odp_random.h b/platform/linux-generic/arch/aarch64/odp_random.h
new file mode 100644
index 000000000..023e6c455
--- /dev/null
+++ b/platform/linux-generic/arch/aarch64/odp_random.h
@@ -0,0 +1,166 @@
+/* Copyright (c) 2021, ARM Limited
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier:     BSD-3-Clause
+ */
+
+#ifndef ODP_AARCH64_RANDOM_H_
+#define ODP_AARCH64_RANDOM_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <odp/api/spec/random.h>
+#include <odp/autoheader_internal.h>
+
+#include <stdint.h>
+
+odp_random_kind_t _odp_random_max_kind_generic(void);
+int32_t _odp_random_true_data_generic(uint8_t *buf, uint32_t len);
+int32_t _odp_random_crypto_data_generic(uint8_t *buf, uint32_t len);
+
+#ifdef __ARM_FEATURE_RNG
+
+#if __ARM_FEATURE_UNALIGNED != 1
+#error This implementation requires unaligned access
+#endif
+
+static inline int _odp_random_max_kind(void)
+{
+	return ODP_RANDOM_TRUE;
+}
+
+static inline int _odp_rndr(uint64_t *v)
+{
+	int pass;
+
+	/* Return a 64-bit random number which is reseeded from the True Random
+	 * Number source. If the hardware returns a genuine random number,
+	 * PSTATE.NZCV is set to 0b0000. The NZCV condition flag is checked via
+	 * the CSET instruction. If the hardware cannot return a genuine random
+	 * number in a reasonable period of time, PSTATE.NZCV is set to 0b0100
+	 * and the data value returned is 0. */
+	__asm__ volatile("mrs   %0, s3_3_c2_c4_0\n\t"
+			 "cset  %w[pass], ne"
+			 : "=r" (*v), [pass] "=r" (pass)
+			 :
+			 : "cc");
+
+	return pass;
+}
+
+static inline int _odp_rndrrs(uint64_t *v)
+{
+	int pass;
+
+	/* Return a 64-bit random number which is reseeded from the True Random
+	 * Number source immediately before the read of the random number.
+	 * If the hardware returns a genuine random number, PSTATE.NZCV is
+	 * set to 0b0000. The NZCV condition flag is checked via the CSET
+	 * instruction. If the hardware cannot return a genuine random number
+	 * in a reasonable period of time, PSTATE.NZCV is set to 0b0100 and the
+	 * data value returned is 0. */
+	__asm__ volatile("mrs   %0, s3_3_c2_c4_1\n\t"
+			 "cset  %w[pass], ne"
+			 : "=r" (*v), [pass] "=r" (pass)
+			 :
+			 : "cc");
+
+	return pass;
+}
+
+static inline int32_t _odp_random_crypto_data(uint8_t *buf, uint32_t len)
+{
+	uint64_t temp;
+
+	for (uint32_t i = 0; i < len / 8; i++) {
+		while (!_odp_rndr(&temp))
+			;
+
+		*(uint64_t *)(uintptr_t)buf = temp;
+		buf += 8;
+	}
+
+	if (len & 7) {
+		while (!_odp_rndr(&temp))
+			;
+
+		if (len & 4) {
+			*(uint32_t *)(uintptr_t)buf = temp & 0xffffffff;
+			temp >>= 32;
+			buf += 4;
+		}
+
+		if (len & 2) {
+			*(uint16_t *)(uintptr_t)buf = temp & 0xffff;
+			temp >>= 16;
+			buf += 2;
+		}
+
+		if (len & 1)
+			*buf = temp & 0xff;
+	}
+
+	return len;
+}
+
+static inline int32_t _odp_random_true_data(uint8_t *buf, uint32_t len)
+{
+	uint64_t temp;
+
+	for (uint32_t i = 0; i < len / 8; i++) {
+		while (!_odp_rndrrs(&temp))
+			;
+
+		*(uint64_t *)(uintptr_t)buf = temp;
+		buf += 8;
+	}
+
+	if (len & 7) {
+		while (!_odp_rndrrs(&temp))
+			;
+
+		if (len & 4) {
+			*(uint32_t *)(uintptr_t)buf = temp & 0xffffffff;
+			temp >>= 32;
+			buf += 4;
+		}
+
+		if (len & 2) {
+			*(uint16_t *)(uintptr_t)buf = temp & 0xffff;
+			temp >>= 16;
+			buf += 2;
+		}
+
+		if (len & 1)
+			*buf = temp & 0xff;
+	}
+
+	return len;
+}
+
+#else
+
+static inline int _odp_random_max_kind(void)
+{
+	return _odp_random_max_kind_generic();
+}
+
+static inline int32_t _odp_random_crypto_data(uint8_t *buf, uint32_t len)
+{
+	return _odp_random_crypto_data_generic(buf, len);
+}
+
+static inline int32_t _odp_random_true_data(uint8_t *buf, uint32_t len)
+{
+	return _odp_random_true_data_generic(buf, len);
+}
+
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif