windows/svc: add new package to help create and manage Windows services

Change-Id: I58bb446aaa387b31d8a9ff4217793a170b96a7e2
Reviewed-on: https://go-review.googlesource.com/9104
Reviewed-by: Rob Pike <r@golang.org>

windows/svc/sys_amd64.s

@@ -0,0 +1,41 @@
+// Copyright 2012 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.
+
+// +build windows
+
+// func servicemain(argc uint32, argv **uint16)
+TEXT ·servicemain(SB),7,$0
+	MOVL	CX, ·sArgc(SB)
+	MOVL	DX, ·sArgv(SB)
+
+	SUBQ	$32, SP		// stack for the first 4 syscall params
+
+	MOVQ	·sName(SB), CX
+	MOVQ	$·servicectlhandler(SB), DX
+	MOVQ	·cRegisterServiceCtrlHandlerW(SB), AX
+	CALL	AX
+	CMPQ	AX, $0
+	JE	exit
+	MOVQ	AX, ·ssHandle(SB)
+
+	MOVQ	·goWaitsH(SB), CX
+	MOVQ	·cSetEvent(SB), AX
+	CALL	AX
+
+	MOVQ	·cWaitsH(SB), CX
+	MOVQ	$4294967295, DX
+	MOVQ	·cWaitForSingleObject(SB), AX
+	CALL	AX
+
+exit:
+	ADDQ	$32, SP
+	RET
+
+// I do not know why, but this seems to be the only way to call
+// ctlHandlerProc on Windows 7.
+
+// func servicectlhandler(ctl uint32) uintptr
+TEXT ·servicectlhandler(SB),7,$0
+	MOVQ	·ctlHandlerProc(SB), AX
+	JMP	AX