Add an Armv8 rndr random number provider

Armv8.5 adds an optional random number generator. This is implemented
as two special registers one to read a random number, the other to
re-seed the entropy pool before reading a random number. Both registers
will set the condition flags to tell the caller they can't produce a
random number in a reasonable amount of time.

Without a signal to reseed the entropy pool use the latter register
to provide random numbers to the kernel pool. If at a later time we
had a way to tell the provider if it needs to reseed or not we could
use the former.

On an Amazon AWS Graviton3 VM this never failed, however this may not
be the case on low end CPUs so retry reading the random number 10 times
before returning an error.

Reviewed by:	imp, delphij (csprng)
Sponsored by:	The FreeBSD Foundation
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D35411

2 files changed, 136 insertions, 0 deletions

diff --git a/sys/dev/random/armv8rng.c b/sys/dev/random/armv8rng.c
new file mode 100644
index 000000000000..3cca42a5bbf3
--- /dev/null
+++ b/sys/dev/random/armv8rng.c
@@ -0,0 +1,135 @@
+/*-
+ * Copyright (c) 2022 The FreeBSD Foundation
+ *
+ * This software was developed by Andrew Turner 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.
+ * 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.
+ */
+
+#include <sys/cdefs.h>
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/conf.h>
+#include <sys/kernel.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/module.h>
+#include <sys/random.h>
+
+#include <machine/armreg.h>
+
+#include <dev/random/randomdev.h>
+
+static u_int random_rndr_read(void *, u_int);
+
+static bool has_rndr;
+static struct random_source random_armv8_rndr = {
+	.rs_ident = "Armv8 rndr RNG",
+	.rs_source = RANDOM_PURE_ARMV8,
+	.rs_read = random_rndr_read,
+};
+
+static inline int
+random_rndr_read_one(u_long *buf)
+{
+	u_long val;
+	int loop, ret;
+
+	loop = 10;
+	do {
+		__asm __volatile(
+		    ".arch_extension rng   \n"
+		    "mrs	%0, rndrrs \n" /* Read the random number */
+		    "cset	%w1, ne    \n" /* 1 on success, 0 on failure */
+		    ".arch_extension norng \n"
+		    : "=&r" (val), "=&r"(ret) :: "cc");
+	} while (ret != 0 && --loop > 0);
+
+	if (ret != 0)
+		*buf = val;
+
+	return (ret);
+}
+
+static u_int
+random_rndr_read(void *buf, u_int c)
+{
+	u_long *b;
+	u_int count;
+
+	b = buf;
+	for (count = 0; count < c; count += sizeof(*b)) {
+		if (!random_rndr_read_one(b))
+			break;
+
+		b++;
+	}
+
+	return (count);
+}
+
+static int
+rndr_modevent(module_t mod, int type, void *unused)
+{
+	uint64_t reg;
+	int error = 0;
+
+	switch (type) {
+	case MOD_LOAD:
+		has_rndr = false;
+		if (get_kernel_reg(ID_AA64ISAR0_EL1, &reg) &&
+		    ID_AA64ISAR0_RNDR_VAL(reg) != ID_AA64ISAR0_RNDR_NONE) {
+			has_rndr = true;
+			random_source_register(&random_armv8_rndr);
+			printf("random: fast provider: \"%s\"\n",
+			    random_armv8_rndr.rs_ident);
+		}
+		break;
+
+	case MOD_UNLOAD:
+		if (has_rndr)
+			random_source_deregister(&random_armv8_rndr);
+		break;
+
+	case MOD_SHUTDOWN:
+		break;
+
+	default:
+		error = EOPNOTSUPP;
+		break;
+
+	}
+
+	return (error);
+}
+
+static moduledata_t rndr_mod = {
+	"rndr",
+	rndr_modevent,
+	0
+};
+
+DECLARE_MODULE(rndr, rndr_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
+MODULE_VERSION(rndr, 1);
+MODULE_DEPEND(rndr, random_harvestq, 1, 1, 1);
diff --git a/sys/dev/random/random_harvestq.c b/sys/dev/random/random_harvestq.c
index 09b81950281b..dce0878513db 100644
--- a/sys/dev/random/random_harvestq.c
+++ b/sys/dev/random/random_harvestq.c
@@ -385,6 +385,7 @@ static const char *random_source_descr[ENTROPYSOURCE] = {
 	[RANDOM_PURE_TPM] = "PURE_TPM",
 	[RANDOM_PURE_VMGENID] = "PURE_VMGENID",
 	[RANDOM_PURE_QUALCOMM] = "PURE_QUALCOMM",
+	[RANDOM_PURE_ARMV8] = "PURE_ARMV8",
 	/* "ENTROPYSOURCE" */
 };