From 0e56c31b85264c35869b3f5c0884beb9e2517110 Mon Sep 17 00:00:00 2001
From: Mikael Urankar <mikael@FreeBSD.org>
Date: Mon, 19 Sep 2022 18:46:36 +0200
Subject: [PATCH] runtime: Add vdso on freebsd/riscv64

Use rdtime to retrieve the timecounter, same as the FreeBSD libc.

Updates #53466

Change-Id: I48816e9100036f1ef483e4d3afcf10db0d3b85f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/443036
Reviewed-by: Meng Zhuo <mzh@golangcn.org>
Reviewed-by: Dmitri Goutnik <dgoutnik@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Yuval Pavel Zholkover <paulzhol@gmail.com>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
---
 src/runtime/sys_freebsd_riscv64.s   |  6 ++++++
 src/runtime/vdso_freebsd_riscv64.go | 13 ++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/runtime/sys_freebsd_riscv64.s b/src/runtime/sys_freebsd_riscv64.s
index 4b8699e2bf..30deed2573 100644
--- a/src/runtime/sys_freebsd_riscv64.s
+++ b/src/runtime/sys_freebsd_riscv64.s
@@ -428,3 +428,9 @@ TEXT runtime·closeonexec(SB),NOSPLIT|NOFRAME,$0
 	MOV	$SYS_fcntl, T0
 	ECALL
 	RET
+
+// func getCntxct() uint32
+TEXT runtime·getCntxct(SB),NOSPLIT|NOFRAME,$0
+	RDTIME	A0
+	MOVW	A0, ret+0(FP)
+	RET
diff --git a/src/runtime/vdso_freebsd_riscv64.go b/src/runtime/vdso_freebsd_riscv64.go
index ce2dd9c439..a4fff4b1db 100644
--- a/src/runtime/vdso_freebsd_riscv64.go
+++ b/src/runtime/vdso_freebsd_riscv64.go
@@ -4,7 +4,18 @@
 
 package runtime
 
+const (
+	_VDSO_TH_ALGO_RISCV_RDTIME = 1
+)
+
+func getCntxct() uint32
+
 //go:nosplit
 func (th *vdsoTimehands) getTimecounter() (uint32, bool) {
-	return 0, false
+	switch th.algo {
+	case _VDSO_TH_ALGO_RISCV_RDTIME:
+		return getCntxct(), true
+	default:
+		return 0, false
+	}
 }
-- 
2.50.0