Add Arm Assembly (aarch64) support for RNG

Include aarch64 asm instructions for random number generation using the
RNDR and RNDRRS instructions. Provide detection functions for RNDR and
RNDRRS getauxval.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15361)

1 files changed, 60 insertions, 0 deletions

diff --git a/crypto/arm64cpuid.pl b/crypto/arm64cpuid.pl
index 11f0e50279..a86fa6073a 100755
--- a/crypto/arm64cpuid.pl
+++ b/crypto/arm64cpuid.pl
@@ -161,7 +161,67 @@ CRYPTO_memcmp:
 	lsr	w0,w0,#31
 	ret
 .size	CRYPTO_memcmp,.-CRYPTO_memcmp
+
+.globl	_armv8_rng_probe
+.type	_armv8_rng_probe,%function
+_armv8_rng_probe:
+	mrs	x0, s3_3_c2_c4_0	// rndr
+	mrs	x0, s3_3_c2_c4_1	// rndrrs
+	ret
+.size	_armv8_rng_probe,.-_armv8_rng_probe
+___
+
+sub gen_random {
+my $rdop = shift;
+my $rand_reg = $rdop eq "rndr" ? "s3_3_c2_c4_0" : "s3_3_c2_c4_1";
+
+print<<___;
+// Fill buffer with Randomly Generated Bytes
+// inputs:  char * in x0 - Pointer to buffer
+//          size_t in x1 - Number of bytes to write to buffer
+// outputs: size_t in x0 - Number of bytes successfully written to buffer
+.globl	OPENSSL_${rdop}_asm
+.type	OPENSSL_${rdop}_asm,%function
+.align	4
+OPENSSL_${rdop}_asm:
+	mov	x2,xzr
+	mov	x3,xzr
+
+.align	4
+.Loop_${rdop}:
+	cmp	x1,#0
+	b.eq	.${rdop}_done
+	mov	x3,xzr
+	mrs	x3,$rand_reg
+	b.eq	.${rdop}_done
+
+	cmp	x1,#8
+	b.lt	.Loop_single_byte_${rdop}
+
+	str	x3,[x0]
+	add	x0,x0,#8
+	add	x2,x2,#8
+	subs	x1,x1,#8
+	b.ge	.Loop_${rdop}
+
+.align	4
+.Loop_single_byte_${rdop}:
+	strb	w3,[x0]
+	lsr	x3,x3,#8
+	add	x2,x2,#1
+	add	x0,x0,#1
+	subs	x1,x1,#1
+	b.gt	.Loop_single_byte_${rdop}
+
+.align	4
+.${rdop}_done:
+	mov	x0,x2
+	ret
+.size	OPENSSL_${rdop}_asm,.-OPENSSL_${rdop}_asm
 ___
+}
+gen_random("rndr");
+gen_random("rndrrs");
 
 print $code;
 close STDOUT or die "error closing STDOUT: $!";