runtime: convert a few traceback-related functions from proc.c to traceback.go

They were in proc.c mainly because there was no portable
traceback source file. As part of converting them to Go,
move to traceback.go.

In order to get access to the PC of _rt0_go,
rename to runtime.rt0_go.

LGTM=r
R=golang-codereviews, r
CC=dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/139110043

src/cmd/api/goapi.go

@@ -405,7 +405,17 @@ func (w *Walker) parseFile(dir, file string) (*ast.File, error) {
 			" wincallbackcontext struct{};" +
 			" _select struct{}; " +
 			"); " +
-			"const ( cb_max = 2000 )"
+			"const (" +
+			" cb_max = 2000;" +
+			" _Gidle = 1;" +
+			" _Grunnable = 2;" +
+			" _Grunning = 3;" +
+			" _Gsyscall = 4;" +
+			" _Gwaiting = 5;" +
+			" _Gdead = 6;" +
+			" _Genqueue = 7;" +
+			" _Gcopystack = 8;" +
+			")"
 		f, err = parser.ParseFile(fset, filename, src, 0)
 		if err != nil {
 			log.Fatalf("incorrect generated file: %s", err)

src/pkg/runtime/asm_386.s

@@ -6,7 +6,7 @@
 #include "funcdata.h"
 #include "../../cmd/ld/textflag.h"
 
-TEXT _rt0_go(SB),NOSPLIT,$0
+TEXT runtime·rt0_go(SB),NOSPLIT,$0
 	// copy arguments forward on an even stack
 	MOVL	argc+0(FP), AX
 	MOVL	argv+4(FP), BX

src/pkg/runtime/asm_amd64.s

@@ -6,7 +6,7 @@
 #include "funcdata.h"
 #include "../../cmd/ld/textflag.h"
 
-TEXT _rt0_go(SB),NOSPLIT,$0
+TEXT runtime·rt0_go(SB),NOSPLIT,$0
 	// copy arguments forward on an even stack
 	MOVQ	DI, AX		// argc
 	MOVQ	SI, BX		// argv

src/pkg/runtime/asm_amd64p32.s

@@ -6,7 +6,7 @@
 #include "funcdata.h"
 #include "../../cmd/ld/textflag.h"
 
-TEXT _rt0_go(SB),NOSPLIT,$0
+TEXT runtime·rt0_go(SB),NOSPLIT,$0
 	// copy arguments forward on an even stack
 	MOVL	argc+0(FP), AX
 	MOVL	argv+4(FP), BX

src/pkg/runtime/asm_arm.s

@@ -7,7 +7,7 @@
 #include "../../cmd/ld/textflag.h"
 
 // using frame size $-4 means do not save LR on stack.
-TEXT _rt0_go(SB),NOSPLIT,$-4
+TEXT runtime·rt0_go(SB),NOSPLIT,$-4
 	MOVW	$0xcafebabe, R12
 
 	// copy arguments forward on an even stack

src/pkg/runtime/proc.c

@@ -185,8 +185,6 @@ runtime·schedinit(void)
 	if(p != nil && !runtime·strcmp(p, (byte*)"0"))
 		runtime·copystack = false;
 
-	mstats.enablegc = 1;
-
 	if(runtime·buildVersion.str == nil) {
 		// Condition should never trigger.  This code just serves
 		// to ensure runtime·buildVersion is kept in the resulting binary.
@@ -244,7 +242,10 @@ runtime·main(void)
 
 	if(g->m != &runtime·m0)
 		runtime·throw("runtime·main not on m0");
+
 	runtime·init();
+	mstats.enablegc = 1; // now that runtime is initialized, GC is okay
+
 	main·init();
 
 	if(g->defer != &d || d.fn != &initDone)
@@ -268,118 +269,12 @@ runtime·main(void)
 		*(int32*)runtime·main = 0;
 }
 
-void
-runtime·goroutineheader(G *gp)
-{
-	String status;
-	int64 waitfor;
-	uint32 gpstatus;
-
-	gpstatus = runtime·readgstatus(gp);
-	switch(gpstatus) {
-	case Gidle:
-		status = runtime·gostringnocopy((byte*)"idle");
-		break;
-	case Grunnable:
-		status = runtime·gostringnocopy((byte*)"runnable");
-		break;
-	case Grunning:
-		status = runtime·gostringnocopy((byte*)"running");
-		break;
-	case Gsyscall:
-		status = runtime·gostringnocopy((byte*)"syscall");
-		break;
-	case Gwaiting:
-		if(gp->waitreason.str != nil)
-			status = gp->waitreason;
-		else
-			status = runtime·gostringnocopy((byte*)"waiting");
-		break;
-	case Gscan:
-		status = runtime·gostringnocopy((byte*)"scan");
-		break;
-	case Gscanrunnable:
-		status =  runtime·gostringnocopy((byte*)"scanrunnable");
-		break;
-	case Gscanrunning:
-		status = runtime·gostringnocopy((byte*)"scanrunning");
-		break;
-	case Gscansyscall:
-		status = runtime·gostringnocopy((byte*)"scansyscall");
-		break;
-	case Gscanenqueue:
-		status = runtime·gostringnocopy((byte*)"scanenqueue");
-		break;
-	case Gscanwaiting:
-		if(gp->waitreason.str != nil)
-			status = gp->waitreason;
-		else
-			status = runtime·gostringnocopy((byte*)"scanwaiting");
-		break;
-	case Gcopystack:
-		status = runtime·gostringnocopy((byte*)"copystack");
-		break;
-	default:
-		status = runtime·gostringnocopy((byte*)"???");
-		break;
-	}
-
-	// approx time the G is blocked, in minutes
-	waitfor = 0;
-	gpstatus = gpstatus&~Gscan; // drop the scan bit
-	if((gpstatus == Gwaiting || gpstatus == Gsyscall) && gp->waitsince != 0)
-		waitfor = (runtime·nanotime() - gp->waitsince) / (60LL*1000*1000*1000);
-
-	runtime·printf("goroutine %D [%S", gp->goid, status);
-	if(waitfor >= 1)
-		runtime·printf(", %D minutes", waitfor);
-	if(gp->lockedm != nil)
-		runtime·printf(", locked to thread");
-	runtime·printf("]:\n");
-}
-
 static void
 dumpgstatus(G* gp)
 {
 	runtime·printf("runtime: gp=%p, goid=%D, gp->atomicstatus=%d\n", gp, gp->goid, runtime·readgstatus(gp));
 }
 
-void
-runtime·tracebackothers(G *me)
-{
-	G *gp;
-	int32 traceback;
-	uintptr i;
-	uint32 status;
-
-	traceback = runtime·gotraceback(nil);
-	
-	// Show the current goroutine first, if we haven't already.
-	if((gp = g->m->curg) != nil && gp != me) {
-		runtime·printf("\n");
-		runtime·goroutineheader(gp);
-		runtime·traceback(~(uintptr)0, ~(uintptr)0, 0, gp);
-	}
-
-	runtime·lock(&allglock);
-	for(i = 0; i < runtime·allglen; i++) {
-		gp = runtime·allg[i];
-		if(gp == me || gp == g->m->curg || runtime·readgstatus(gp) == Gdead)
-			continue;
-		if(gp->issystem && traceback < 2)
-			continue;
-		runtime·printf("\n");
-		runtime·goroutineheader(gp);
-		status = runtime·readgstatus(gp);
-		if((status&~Gscan) == Grunning){
-			runtime·printf("\tgoroutine running on other thread; stack unavailable\n");
-			runtime·printcreatedby(gp);
-		} else
-			runtime·traceback(~(uintptr)0, ~(uintptr)0, 0, gp);
-	}
-	runtime·unlock(&allglock);
-}
-
 static void
 checkmcount(void)
 {
@@ -3373,23 +3268,6 @@ runtime·testSchedLocalQueueSteal(void)
 	}
 }
 
-extern void runtime·morestack(void);
-uintptr runtime·externalthreadhandlerp;
-
-// Does f mark the top of a goroutine stack?
-bool
-runtime·topofstack(Func *f)
-{
-	return f->entry == (uintptr)runtime·goexit ||
-		f->entry == (uintptr)runtime·mstart ||
-		f->entry == (uintptr)runtime·mcall ||
-		f->entry == (uintptr)runtime·onM ||
-		f->entry == (uintptr)runtime·morestack ||
-		f->entry == (uintptr)runtime·lessstack ||
-		f->entry == (uintptr)_rt0_go ||
-		(runtime·externalthreadhandlerp != 0 && f->entry == runtime·externalthreadhandlerp);
-}
-
 void
 runtime·setmaxthreads_m(void)
 {

src/pkg/runtime/rt0_darwin_386.s

@@ -13,4 +13,4 @@ TEXT _rt0_386_darwin(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_darwin_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_darwin(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_dragonfly_386.s

@@ -13,4 +13,4 @@ TEXT _rt0_386_dragonfly(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_dragonfly_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_dragonfly(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_freebsd_386.s

@@ -13,4 +13,4 @@ TEXT _rt0_386_freebsd(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_freebsd_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_freebsd(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_freebsd_arm.s

@@ -10,9 +10,9 @@ TEXT _rt0_arm_freebsd(SB),NOSPLIT,$-4
 	MOVW	(R13), R0	// argc
 	MOVW	$4(R13), R1		// argv
 	MOVM.DB.W [R0-R1], (R13)
-	B	_rt0_go(SB)
+	B	runtime·rt0_go(SB)
 
 TEXT main(SB),NOSPLIT,$-4
 	MOVM.DB.W [R0-R1], (R13)
-	MOVW	$_rt0_go(SB), R4
+	MOVW	$runtime·rt0_go(SB), R4
 	B		(R4)

src/pkg/runtime/rt0_linux_386.s

@@ -14,7 +14,7 @@ TEXT _rt0_386_linux(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)
 
 TEXT _fallback_vdso(SB),NOSPLIT,$0
 	INT	$0x80

src/pkg/runtime/rt0_linux_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_linux(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_linux_arm.s

@@ -56,7 +56,7 @@ TEXT _rt0_arm_linux1(SB),NOSPLIT,$-4
 	SUB	$4, R13 // fake a stack frame for runtime·setup_auxv
 	BL	runtime·setup_auxv(SB)
 	ADD	$4, R13
-	B	_rt0_go(SB)
+	B	runtime·rt0_go(SB)
 
 TEXT bad_abi<>(SB),NOSPLIT,$-4
 	// give diagnosis and exit

src/pkg/runtime/rt0_nacl_386.s

@@ -19,4 +19,4 @@ TEXT _rt0_386_nacl(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_nacl_amd64p32.s

@@ -27,4 +27,4 @@ TEXT main(SB),NOSPLIT,$0
 	// Uncomment for fake time like on Go Playground.
 	//MOVQ	$1257894000000000000, AX
 	//MOVQ	AX, runtime·timens(SB)
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_nacl_arm.s

@@ -17,4 +17,4 @@ TEXT _rt0_arm_nacl(SB),NOSPLIT,$-4
 	B	main(SB)
 
 TEXT main(SB),NOSPLIT,$0
-	B	_rt0_go(SB)
+	B	runtime·rt0_go(SB)

src/pkg/runtime/rt0_netbsd_386.s

@@ -13,4 +13,4 @@ TEXT _rt0_386_netbsd(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_netbsd_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_netbsd(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_netbsd_arm.s

@@ -10,4 +10,4 @@ TEXT _rt0_arm_netbsd(SB),NOSPLIT,$-4
 	MOVW	(R13), R0	// argc
 	MOVW	$4(R13), R1		// argv
 	MOVM.DB.W [R0-R1], (R13)
-	B _rt0_go(SB)
+	B runtime·rt0_go(SB)

src/pkg/runtime/rt0_openbsd_386.s

@@ -13,4 +13,4 @@ TEXT _rt0_386_openbsd(SB),NOSPLIT,$8
 	INT	$3
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)

src/pkg/runtime/rt0_openbsd_amd64.s

@@ -11,5 +11,5 @@ TEXT _rt0_amd64_openbsd(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX

src/pkg/runtime/rt0_plan9_386.s

@@ -14,7 +14,7 @@ TEXT _rt0_386_plan9(SB),NOSPLIT,$12
 	MOVL	AX, 0(SP)
 	LEAL	inargv+0(FP), AX
 	MOVL	AX, 4(SP)
-	CALL	_rt0_go(SB)
+	CALL	runtime·rt0_go(SB)
 
 DATA  runtime·isplan9(SB)/4, $1
 GLOBL runtime·isplan9(SB), $4

src/pkg/runtime/rt0_plan9_amd64.s

@@ -11,7 +11,7 @@ TEXT _rt0_amd64_plan9(SB),NOSPLIT,$24
 	MOVL	$1, _nprivates(SB)
 	MOVL	inargc-8(FP), DI
 	LEAQ	inargv+0(FP), SI
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
 
 DATA runtime·isplan9(SB)/4, $1

src/pkg/runtime/rt0_solaris_amd64.s

@@ -11,7 +11,7 @@ TEXT _rt0_amd64_solaris(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
 
 DATA runtime·issolaris(SB)/4, $1

src/pkg/runtime/rt0_windows_386.s

@@ -13,7 +13,7 @@ TEXT _rt0_386_windows(SB),NOSPLIT,$12
 	JMP	main(SB)
 
 TEXT main(SB),NOSPLIT,$0
-	JMP	_rt0_go(SB)
+	JMP	runtime·rt0_go(SB)
 
 
 DATA  runtime·iswindows(SB)/4, $1

src/pkg/runtime/rt0_windows_amd64.s

@@ -12,7 +12,7 @@ TEXT _rt0_amd64_windows(SB),NOSPLIT,$-8
 	JMP	AX
 
 TEXT main(SB),NOSPLIT,$-8
-	MOVQ	$_rt0_go(SB), AX
+	MOVQ	$runtime·rt0_go(SB), AX
 	JMP	AX
 
 DATA  runtime·iswindows(SB)/4, $1

src/pkg/runtime/runtime.h

@@ -882,7 +882,6 @@ void	runtime·netpolllock(PollDesc*);
 void	runtime·netpollunlock(PollDesc*);
 void	runtime·crash(void);
 void	runtime·parsedebugvars(void);
-void	_rt0_go(void);
 void*	runtime·funcdata(Func*, int32);
 void	runtime·setmaxthreads_m(void);
 G*	runtime·timejump(void);

src/pkg/runtime/stubs.go

@@ -138,9 +138,6 @@ func entersyscall()
 func entersyscallblock()
 func exitsyscall()
 
-func goroutineheader(gp *g)
-func tracebackothers(gp *g)
-
 func cgocallback(fn, frame unsafe.Pointer, framesize uintptr)
 func gogo(buf *gobuf)
 func gosave(buf *gobuf)
@@ -260,4 +257,3 @@ var newproc, deferproc, lessstack struct{} // C/assembly functions
 func funcspdelta(*_func, uintptr) int32 // symtab.c
 func funcarglen(*_func, uintptr) int32  // symtab.c
 const _ArgsSizeUnknown = -0x80000000    // funcdata.h
-func topofstack(*_func) bool            // proc.c

src/pkg/runtime/traceback.go

@@ -32,12 +32,7 @@ const usesLR = GOARCH != "amd64" && GOARCH != "amd64p32" && GOARCH != "386"
 
 // jmpdeferPC is the PC at the beginning of the jmpdefer assembly function.
 // The traceback needs to recognize it on link register architectures.
-var jmpdeferPC uintptr
-
-func init() {
-	f := jmpdefer
-	jmpdeferPC = **(**uintptr)(unsafe.Pointer(&f))
-}
+var jmpdeferPC = funcPC(jmpdefer)
 
 // System-specific hook. See traceback_windows.go
 var systraceback func(*_func, *stkframe, *g, bool, func(*stkframe, unsafe.Pointer) bool, unsafe.Pointer) (changed, aborted bool)
@@ -502,3 +497,117 @@ func callers(skip int, pcbuf *uintptr, m int) int {
 func gcallers(gp *g, skip int, pcbuf *uintptr, m int) int {
 	return gentraceback(^uintptr(0), ^uintptr(0), 0, gp, skip, pcbuf, m, nil, nil, false)
 }
+
+var gStatusStrings = [...]string{
+	_Gidle:      "idle",
+	_Grunnable:  "runnable",
+	_Grunning:   "running",
+	_Gsyscall:   "syscall",
+	_Gwaiting:   "waiting",
+	_Gdead:      "dead",
+	_Genqueue:   "enqueue",
+	_Gcopystack: "copystack",
+}
+
+var gScanStatusStrings = [...]string{
+	0:          "scan",
+	_Grunnable: "scanrunnable",
+	_Grunning:  "scanrunning",
+	_Gsyscall:  "scansyscall",
+	_Gwaiting:  "scanwaiting",
+	_Gdead:     "scandead",
+	_Genqueue:  "scanenqueue",
+}
+
+func goroutineheader(gp *g) {
+	gpstatus := readgstatus(gp)
+
+	// Basic string status
+	var status string
+	if 0 <= gpstatus && gpstatus < uint32(len(gStatusStrings)) {
+		status = gStatusStrings[gpstatus]
+	} else if gpstatus&_Gscan != 0 && 0 <= gpstatus&^_Gscan && gpstatus&^_Gscan < uint32(len(gStatusStrings)) {
+		status = gStatusStrings[gpstatus&^_Gscan]
+	} else {
+		status = "???"
+	}
+
+	// Override.
+	if (gpstatus == _Gwaiting || gpstatus == _Gscanwaiting) && gp.waitreason != "" {
+		status = gp.waitreason
+	}
+
+	// approx time the G is blocked, in minutes
+	var waitfor int64
+	gpstatus &^= _Gscan // drop the scan bit
+	if (gpstatus == _Gwaiting || gpstatus == _Gsyscall) && gp.waitsince != 0 {
+		waitfor = (nanotime() - gp.waitsince) / 60e9
+	}
+	print("goroutine ", gp.goid, " [", status)
+	if waitfor >= 1 {
+		print(", ", waitfor, " minutes")
+	}
+	if gp.lockedm != nil {
+		print(", locked to thread")
+	}
+	print("]:\n")
+}
+
+func tracebackothers(me *g) {
+	level := gotraceback(nil)
+
+	// Show the current goroutine first, if we haven't already.
+	g := getg()
+	gp := g.m.curg
+	if gp != nil && gp != me {
+		print("\n")
+		goroutineheader(gp)
+		traceback(^uintptr(0), ^uintptr(0), 0, gp)
+	}
+
+	lock(&allglock)
+	for _, gp := range allgs {
+		if gp == me || gp == g.m.curg || readgstatus(gp) == _Gdead || gp.issystem && level < 2 {
+			continue
+		}
+		print("\n")
+		goroutineheader(gp)
+		if readgstatus(gp)&^_Gscan == _Grunning {
+			print("\tgoroutine running on other thread; stack unavailable\n")
+			printcreatedby(gp)
+		} else {
+			traceback(^uintptr(0), ^uintptr(0), 0, gp)
+		}
+	}
+	unlock(&allglock)
+}
+
+func goexit()
+func mstart()
+func morestack()
+func rt0_go()
+
+var (
+	goexitPC    = funcPC(goexit)
+	mstartPC    = funcPC(mstart)
+	mcallPC     = funcPC(mcall)
+	onMPC       = funcPC(onM)
+	morestackPC = funcPC(morestack)
+	lessstackPC = funcPC(lessstack)
+	rt0_goPC    = funcPC(rt0_go)
+
+	externalthreadhandlerp uintptr // initialized elsewhere
+)
+
+// Does f mark the top of a goroutine stack?
+func topofstack(f *_func) bool {
+	pc := f.entry
+	return pc == goexitPC ||
+		pc == mstartPC ||
+		pc == mcallPC ||
+		pc == onMPC ||
+		pc == morestackPC ||
+		pc == lessstackPC ||
+		pc == rt0_goPC ||
+		externalthreadhandlerp != 0 && pc == externalthreadhandlerp
+}

src/pkg/runtime/traceback_windows.go

@@ -13,8 +13,7 @@ var sigtrampPC uintptr
 var sigtramp struct{} // assembly function
 
 func init() {
-	f := sigtramp
-	sigtrampPC = **(**uintptr)(unsafe.Pointer(&f))
+	sigtrampPC = funcPC(sigtramp)
 	systraceback = traceback_windows
 }