runtime: handle morestack/lessstack in stack trace

If we start a garbage collection on g0 during a
stack split or unsplit, we'll see morestack or lessstack
at the top of the stack. Record an argument frame size
for those, and record that they terminate the stack.

R=golang-dev, dvyukov
CC=golang-dev
https://golang.org/cl/11533043

src/pkg/runtime/asm_386.s

@@ -195,7 +195,12 @@ TEXT runtime·mcall(SB), 7, $0-4
  */
 
 // Called during function prolog when more stack is needed.
-TEXT runtime·morestack(SB),7,$0
+//
+// The traceback routines see morestack on a g0 as being
+// the top of a stack (for example, morestack calling newstack
+// calling the scheduler calling newm calling gc), so we must
+// record an argument size. For that purpose, it has no arguments.
+TEXT runtime·morestack(SB),7,$0-0
 	// Cannot grow scheduler stack (m->g0).
 	get_tls(CX)
 	MOVL	m(CX), BX
@@ -288,7 +293,10 @@ TEXT reflect·call(SB), 7, $0-12
 
 
 // Return point when leaving stack.
-TEXT runtime·lessstack(SB), 7, $0
+//
+// Lessstack can appear in stack traces for the same reason
+// as morestack; in that context, it has 0 arguments.
+TEXT runtime·lessstack(SB), 7, $0-0
 	// Save return value in m->cret
 	get_tls(CX)
 	MOVL	m(CX), BX

src/pkg/runtime/asm_amd64.s

@@ -186,7 +186,12 @@ TEXT runtime·mcall(SB), 7, $0-8
 
 // Called during function prolog when more stack is needed.
 // Caller has already done get_tls(CX); MOVQ m(CX), BX.
-TEXT runtime·morestack(SB),7,$0
+//
+// The traceback routines see morestack on a g0 as being
+// the top of a stack (for example, morestack calling newstack
+// calling the scheduler calling newm calling gc), so we must
+// record an argument size. For that purpose, it has no arguments.
+TEXT runtime·morestack(SB),7,$0-0
 	// Cannot grow scheduler stack (m->g0).
 	MOVQ	m_g0(BX), SI
 	CMPQ	g(CX), SI
@@ -268,7 +273,10 @@ TEXT reflect·call(SB), 7, $0-20
 	RET
 
 // Return point when leaving stack.
-TEXT runtime·lessstack(SB), 7, $0
+//
+// Lessstack can appear in stack traces for the same reason
+// as morestack; in that context, it has 0 arguments.
+TEXT runtime·lessstack(SB), 7, $0-0
 	// Save return value in m->cret
 	get_tls(CX)
 	MOVQ	m(CX), BX

src/pkg/runtime/asm_arm.s

@@ -170,7 +170,12 @@ TEXT runtime·mcall(SB), 7, $-4-4
 // NB. we do not save R0 because we've forced 5c to pass all arguments
 // on the stack.
 // using frame size $-4 means do not save LR on stack.
-TEXT runtime·morestack(SB),7,$-4
+//
+// The traceback routines see morestack on a g0 as being
+// the top of a stack (for example, morestack calling newstack
+// calling the scheduler calling newm calling gc), so we must
+// record an argument size. For that purpose, it has no arguments.
+TEXT runtime·morestack(SB),7,$-4-0
 	// Cannot grow scheduler stack (m->g0).
 	MOVW	m_g0(m), R4
 	CMP	g, R4
@@ -197,7 +202,7 @@ TEXT runtime·morestack(SB),7,$-4
 	// Call newstack on m->g0's stack.
 	MOVW	m_g0(m), g
 	MOVW	(g_sched+gobuf_sp)(g), SP
-	B	runtime·newstack(SB)
+	BL	runtime·newstack(SB)
 
 // Called from reflection library.  Mimics morestack,
 // reuses stack growth code to create a frame
@@ -241,14 +246,17 @@ TEXT reflect·call(SB), 7, $-4-12
 
 // Return point when leaving stack.
 // using frame size $-4 means do not save LR on stack.
-TEXT runtime·lessstack(SB), 7, $-4
+//
+// Lessstack can appear in stack traces for the same reason
+// as morestack; in that context, it has 0 arguments.
+TEXT runtime·lessstack(SB), 7, $-4-0
 	// Save return value in m->cret
 	MOVW	R0, m_cret(m)
 
 	// Call oldstack on m->g0's stack.
 	MOVW	m_g0(m), g
 	MOVW	(g_sched+gobuf_sp)(g), SP
-	B	runtime·oldstack(SB)
+	BL	runtime·oldstack(SB)
 
 // void jmpdefer(fn, sp);
 // called from deferreturn.

src/pkg/runtime/proc.c

@@ -2499,17 +2499,6 @@ runtime·testSchedLocalQueueSteal(void)
 
 extern void runtime·morestack(void);
 
-bool
-runtime·haszeroargs(uintptr pc)
-{
-	return pc == (uintptr)runtime·goexit ||
-		pc == (uintptr)runtime·mcall ||
-		pc == (uintptr)runtime·mstart ||
-		pc == (uintptr)runtime·lessstack ||
-		pc == (uintptr)runtime·morestack ||
-		pc == (uintptr)_rt0_go;
-}
-
 // Does f mark the top of a goroutine stack?
 bool
 runtime·topofstack(Func *f)
@@ -2517,5 +2506,7 @@ runtime·topofstack(Func *f)
 	return f->entry == (uintptr)runtime·goexit ||
 		f->entry == (uintptr)runtime·mstart ||
 		f->entry == (uintptr)runtime·mcall ||
+		f->entry == (uintptr)runtime·morestack ||
+		f->entry == (uintptr)runtime·lessstack ||
 		f->entry == (uintptr)_rt0_go;
 }

src/pkg/runtime/traceback_arm.c

@@ -69,7 +69,8 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 			f = runtime·findfunc(frame.pc);
 			if(f == nil) {
 				runtime·printf("runtime: unknown pc %p after stack split\n", frame.pc);
-				runtime·throw("unknown pc");
+				if(callback != nil)
+					runtime·throw("unknown pc");
 			}
 			frame.fn = f;
 			continue;
@@ -89,7 +90,8 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 			flr = runtime·findfunc(frame.lr);
 			if(flr == nil) {
 				runtime·printf("runtime: unexpected return pc for %s called from %p\n", runtime·funcname(f), frame.lr);
-				runtime·throw("unknown caller pc");
+				if(callback != nil)
+					runtime·throw("unknown caller pc");
 			}
 		}
 			
@@ -112,7 +114,7 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 			else {
 				runtime·printf("runtime: unknown argument frame size for %s called from %p [%s]\n",
 					runtime·funcname(f), frame.lr, flr ? runtime·funcname(flr) : "?");
-				if(!printing)
+				if(callback != nil)
 					runtime·throw("invalid stack");
 				frame.arglen = 0;
 			}
@@ -131,7 +133,8 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 		} else {
 			if(f->locals > frame.fp - frame.sp) {
 				runtime·printf("runtime: inconsistent locals=%p frame=%p fp=%p sp=%p for %s\n", (uintptr)f->locals, (uintptr)f->frame, frame.fp, frame.sp, runtime·funcname(f));
-				runtime·throw("invalid stack");
+				if(callback != nil)
+					runtime·throw("invalid stack");
 			}
 			frame.varp = (byte*)frame.fp - f->locals;
 			frame.varlen = f->locals;

src/pkg/runtime/traceback_x86.c

@@ -83,7 +83,8 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 			f = runtime·findfunc(frame.pc);
 			if(f == nil) {
 				runtime·printf("runtime: unknown pc %p after stack split\n", frame.pc);
-				runtime·throw("unknown pc");
+				if(callback != nil)
+					runtime·throw("unknown pc");
 			}
 			frame.fn = f;
 			continue;
@@ -104,8 +105,9 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 				frame.lr = ((uintptr*)frame.fp)[-1];
 			flr = runtime·findfunc(frame.lr);
 			if(flr == nil) {
-				runtime·printf("runtime: unexpected return pc for %s called from %p", runtime·funcname(f), frame.lr);
-				runtime·throw("unknown caller pc");
+				runtime·printf("runtime: unexpected return pc for %s called from %p\n", runtime·funcname(f), frame.lr);
+				if(callback != nil)
+					runtime·throw("unknown caller pc");
 			}
 		}
 
@@ -128,7 +130,7 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 			else {
 				runtime·printf("runtime: unknown argument frame size for %s called from %p [%s]\n",
 					runtime·funcname(f), frame.lr, flr ? runtime·funcname(flr) : "?");
-				if(!printing)
+				if(callback != nil)
 					runtime·throw("invalid stack");
 				frame.arglen = 0;
 			}
@@ -147,7 +149,8 @@ runtime·gentraceback(uintptr pc0, uintptr sp0, uintptr lr0, G *gp, int32 skip,
 		} else {
 			if(f->locals > frame.fp - sizeof(uintptr) - frame.sp) {
 				runtime·printf("runtime: inconsistent locals=%p frame=%p fp=%p sp=%p for %s\n", (uintptr)f->locals, (uintptr)f->frame, frame.fp, frame.sp, runtime·funcname(f));
-				runtime·throw("invalid stack");
+				if(callback != nil)
+					runtime·throw("invalid stack");
 			}
 			frame.varp = (byte*)frame.fp - sizeof(uintptr) - f->locals;
 			frame.varlen = f->locals;