runtime: make framepointer mode safe for Windows

A few other architectures have already defined a NOFRAME flag.
Use it to disable frame pointer code on a few very low-level functions
that must behave like Windows code.

Makes the failing os/signal test pass on a Windows gomote.

Change-Id: I982365f2c59a0aa302b4428c970846c61027cf3e
Reviewed-on: https://go-review.googlesource.com/23456Reviewed-by: Austin Clements <austin@google.com>

src/cmd/internal/obj/x86/obj6.go

@@ -610,12 +610,11 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	}
 
 	var bpsize int
-	if p.Mode == 64 && obj.Framepointer_enabled != 0 && autoffset > 0 {
+	if p.Mode == 64 && obj.Framepointer_enabled != 0 && autoffset > 0 && p.From3.Offset&obj.NOFRAME == 0 {
 		// Make room for to save a base pointer. If autoffset == 0,
 		// this might do something special like a tail jump to
 		// another function, so in that case we omit this.
 		bpsize = ctxt.Arch.PtrSize
-
 		autoffset += int32(bpsize)
 		p.To.Offset += int64(bpsize)
 	} else {

src/runtime/sys_windows_amd64.s

@@ -11,7 +11,7 @@
 #define maxargs 16
 
 // void runtime·asmstdcall(void *c);
-TEXT runtime·asmstdcall(SB),NOSPLIT,$0
+TEXT runtime·asmstdcall(SB),NOSPLIT|NOFRAME,$0
 	// asmcgocall will put first argument into CX.
 	PUSHQ	CX			// save for later
 	MOVQ	libcall_fn(CX), AX
@@ -62,7 +62,7 @@ loadregs:
 
 	RET
 
-TEXT runtime·badsignal2(SB),NOSPLIT,$48
+TEXT runtime·badsignal2(SB),NOSPLIT|NOFRAME,$48
 	// stderr
 	MOVQ	$-12, CX // stderr
 	MOVQ	CX, 0(SP)
@@ -102,7 +102,7 @@ TEXT runtime·setlasterror(SB),NOSPLIT,$0
 // exception record and context pointers.
 // Handler function is stored in AX.
 // Return 0 for 'not handled', -1 for handled.
-TEXT runtime·sigtramp(SB),NOSPLIT,$0-0
+TEXT runtime·sigtramp(SB),NOSPLIT|NOFRAME,$0-0
 	// CX: PEXCEPTION_POINTERS ExceptionInfo
 
 	// DI SI BP BX R12 R13 R14 R15 registers and DF flag are preserved
@@ -190,32 +190,32 @@ done:
 
 	RET
 
-TEXT runtime·exceptiontramp(SB),NOSPLIT,$0
+TEXT runtime·exceptiontramp(SB),NOSPLIT|NOFRAME,$0
 	MOVQ	$runtime·exceptionhandler(SB), AX
 	JMP	runtime·sigtramp(SB)
 
-TEXT runtime·firstcontinuetramp(SB),NOSPLIT,$0-0
+TEXT runtime·firstcontinuetramp(SB),NOSPLIT|NOFRAME,$0-0
 	MOVQ	$runtime·firstcontinuehandler(SB), AX
 	JMP	runtime·sigtramp(SB)
 
-TEXT runtime·lastcontinuetramp(SB),NOSPLIT,$0-0
+TEXT runtime·lastcontinuetramp(SB),NOSPLIT|NOFRAME,$0-0
 	MOVQ	$runtime·lastcontinuehandler(SB), AX
 	JMP	runtime·sigtramp(SB)
 
-TEXT runtime·ctrlhandler(SB),NOSPLIT,$8
+TEXT runtime·ctrlhandler(SB),NOSPLIT|NOFRAME,$8
 	MOVQ	CX, 16(SP)		// spill
 	MOVQ	$runtime·ctrlhandler1(SB), CX
 	MOVQ	CX, 0(SP)
 	CALL	runtime·externalthreadhandler(SB)
 	RET
 
-TEXT runtime·profileloop(SB),NOSPLIT,$8
+TEXT runtime·profileloop(SB),NOSPLIT|NOFRAME,$8
 	MOVQ	$runtime·profileloop1(SB), CX
 	MOVQ	CX, 0(SP)
 	CALL	runtime·externalthreadhandler(SB)
 	RET
 
-TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
+TEXT runtime·externalthreadhandler(SB),NOSPLIT|NOFRAME,$0
 	PUSHQ	BP
 	MOVQ	SP, BP
 	PUSHQ	BX
@@ -228,7 +228,7 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
 	SUBQ	$m__size, SP		// space for M
 	MOVQ	SP, 0(SP)
 	MOVQ	$m__size, 8(SP)
-	CALL	runtime·memclr(SB)	// smashes AX,BX,CX
+	CALL	runtime·memclr(SB)	// smashes AX,BX,CX, maybe BP
 
 	LEAQ	m_tls(SP), CX
 	MOVQ	CX, 0x28(GS)
@@ -239,7 +239,7 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
 
 	MOVQ	SP, 0(SP)
 	MOVQ	$g__size, 8(SP)
-	CALL	runtime·memclr(SB)	// smashes AX,BX,CX
+	CALL	runtime·memclr(SB)	// smashes AX,BX,CX, maybe BP
 	LEAQ	g__size(SP), BX
 	MOVQ	BX, g_m(SP)
 
@@ -430,7 +430,7 @@ ret:
 // Runs on OS stack. duration (in 100ns units) is in BX.
 // The function leaves room for 4 syscall parameters
 // (as per windows amd64 calling convention).
-TEXT runtime·usleep2(SB),NOSPLIT,$48
+TEXT runtime·usleep2(SB),NOSPLIT|NOFRAME,$48
 	MOVQ	SP, AX
 	ANDQ	$~15, SP	// alignment as per Windows requirement
 	MOVQ	AX, 40(SP)
@@ -446,7 +446,7 @@ TEXT runtime·usleep2(SB),NOSPLIT,$48
 	RET
 
 // Runs on OS stack.
-TEXT runtime·switchtothread(SB),NOSPLIT,$0
+TEXT runtime·switchtothread(SB),NOSPLIT|NOFRAME,$0
 	MOVQ	SP, AX
 	ANDQ	$~15, SP	// alignment as per Windows requirement
 	SUBQ	$(48), SP	// room for SP and 4 args as per Windows requirement