Fill in missing functions for plan9 port

Author: rafael2k

src/runtime/os_plan9.go

@@ -587,10 +587,3 @@ func nanotime1() int64 {
 	// fall back to unix time
 	return int64(frombe(t[0]))
 }
-
-//go:nosplit
-func walltime() (sec int64, nsec int32) {
-	var t [1]uint64
-	readtime(&t[0], 1, 1)
-	return timesplit(frombe(t[0]))
-}

src/runtime/os_plan9_386.go

@@ -0,0 +1,12 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+//go:nosplit
+func walltime() (sec int64, nsec int32) {
+	var t [1]uint64
+	readtime(&t[0], 1, 1)
+	return timesplit(frombe(t[0]))
+}

src/runtime/os_plan9_amd64.go

@@ -0,0 +1,12 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+//go:nosplit
+func walltime() (sec int64, nsec int32) {
+	var t [1]uint64
+	readtime(&t[0], 1, 1)
+	return timesplit(frombe(t[0]))
+}

src/runtime/os_plan9_arm.go

@@ -13,3 +13,10 @@ func cputicks() int64 {
 	// runtime·nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
 	return nanotime()
 }
+
+//go:nosplit
+func walltime() (sec int64, nsec int32) {
+	var t [1]uint64
+	readtime(&t[0], 1, 1)
+	return timesplit(frombe(t[0]))
+}

src/runtime/sys_plan9_arm64.s

@@ -101,6 +101,13 @@ TEXT runtime·closefd(SB),NOSPLIT,$0-12
 	MOVWU	R0, ret+8(FP)
 	RET
 
+//func dupfd(old, new int32) int32
+TEXT runtime·dupfd(SB),NOSPLIT,$0-12
+	MOVD	$SYS_DUP, R0
+	SVC	$0
+	MOVWU	R0, ret+8(FP)
+	RET
+
 //func exits(msg *byte)
 TEXT runtime·exits(SB),NOSPLIT,$0-8
 	MOVD    $SYS_EXITS, R0
@@ -135,6 +142,26 @@ TEXT runtime·plan9_tsemacquire(SB),NOSPLIT,$0-20
 	MOVWU	R0, ret+16(FP)
 	RET
 
+// func timesplit(u uint64) (sec int64, nsec int32)
+TEXT runtime·timesplit(SB),NOSPLIT,$0-16
+	// load u (nanoseconds)
+	MOVD	u+0(FP), R0
+
+	// compute sec = u / 1e9
+	MOVD	R0, R1
+	MOVD	$1000000000, R2
+	UDIV	R2, R1		// R1 = R1 / R2  -> seconds
+
+	// compute rem = u - sec * 1e9
+	MOVD	R1, R3
+	MUL	R3, R2		// R2 = sec * 1e9
+	SUB	R2, R0		// R0 = u - (sec*1e9) -> remainder (nsec)
+
+	// store results
+	MOVD	R1, sec+0(FP)
+	MOVWU	R0, nsec+8(FP)
+	RET
+
 //func nsec(*int64) int64
 TEXT runtime·nsec(SB),NOSPLIT|NOFRAME,$0-16
 	MOVD	$SYS_NSEC, R0