runtime: record goroutine creation pc and display in traceback

package main

func main() {
        go func() { *(*int)(nil) = 0 }()
        select{}
}

panic: runtime error: invalid memory address or nil pointer dereference

[signal 0xb code=0x1 addr=0x0 pc=0x1c96]

runtime.panic+0xac /Users/rsc/g/go/src/pkg/runtime/proc.c:1083
        runtime.panic(0x11bf0, 0xf8400011f0)
runtime.panicstring+0xa3 /Users/rsc/g/go/src/pkg/runtime/runtime.c:116
        runtime.panicstring(0x29a57, 0x0)
runtime.sigpanic+0x144 /Users/rsc/g/go/src/pkg/runtime/darwin/thread.c:470
        runtime.sigpanic()
main._func_001+0x16 /Users/rsc/g/go/src/pkg/runtime/x.go:188
        main._func_001()
runtime.goexit /Users/rsc/g/go/src/pkg/runtime/proc.c:150
        runtime.goexit()
----- goroutine created by -----
main.main+0x3d /Users/rsc/g/go/src/pkg/runtime/x.go:4

goroutine 1 [4]:
runtime.gosched+0x77 /Users/rsc/g/go/src/pkg/runtime/proc.c:598
        runtime.gosched()
runtime.block+0x27 /Users/rsc/g/go/src/pkg/runtime/chan.c:680
        runtime.block()
main.main+0x44 /Users/rsc/g/go/src/pkg/runtime/x.go:5
        main.main()
runtime.mainstart+0xf /Users/rsc/g/go/src/pkg/runtime/amd64/asm.s:77
        runtime.mainstart()
runtime.goexit /Users/rsc/g/go/src/pkg/runtime/proc.c:150
        runtime.goexit()
----- goroutine created by -----
_rt0_amd64+0x8e /Users/rsc/g/go/src/pkg/runtime/amd64/asm.s:64

Fixes #1563.

R=r
CC=golang-dev
https://golang.org/cl/4243046

src/pkg/runtime/amd64/traceback.c

@@ -182,6 +182,17 @@ gentraceback(byte *pc0, byte *sp, G *g, int32 skip, uintptr *pcbuf, int32 max)
 		sp = fp;
 		fp = nil;
 	}
+	
+	if(pcbuf == nil && (pc = g->gopc) != 0 && (f = runtime·findfunc(pc)) != nil) {
+		runtime·printf("----- goroutine created by -----\n%S", f->name);
+		if(pc > f->entry)
+			runtime·printf("+%p", (uintptr)(pc - f->entry));
+		tracepc = pc;	// back up to CALL instruction for funcline.
+		if(n > 0 && pc > f->entry)
+			tracepc--;
+		runtime·printf(" %S:%d\n", f->src, runtime·funcline(f, tracepc));
+	}
+		
 	return n;
 }
 

src/pkg/runtime/arm/traceback.c

@@ -175,6 +175,17 @@ gentraceback(byte *pc0, byte *sp, byte *lr0, G *g, int32 skip, uintptr *pcbuf, i
 		if(f->entry == (uintptr)runtime·deferproc || f->entry == (uintptr)runtime·newproc)
 			sp += 12;
 	}
+	
+	if(pcbuf == nil && (pc = g->gopc) != 0 && (f = runtime·findfunc(pc)) != nil) {
+		runtime·printf("----- goroutine created by -----\n%S", f->name);
+		if(pc > f->entry)
+			runtime·printf("+%p", (uintptr)(pc - f->entry));
+		tracepc = pc;	// back up to CALL instruction for funcline.
+		if(n > 0 && pc > f->entry)
+			tracepc -= sizeof(uintptr);
+		runtime·printf(" %S:%d\n", f->src, runtime·funcline(f, tracepc));
+	}
+
 	return n;		
 }
 

src/pkg/runtime/mgc0.c

@@ -585,7 +585,7 @@ runtime·gc(int32 force)
 	if(fp != nil) {
 		// kick off or wake up goroutine to run queued finalizers
 		if(fing == nil)
-			fing = runtime·newproc1((byte*)runfinq, nil, 0, 0);
+			fing = runtime·newproc1((byte*)runfinq, nil, 0, 0, runtime·gc);
 		else if(fingwait) {
 			fingwait = 0;
 			runtime·ready(fing);

src/pkg/runtime/proc.c

@@ -884,11 +884,11 @@ runtime·newproc(int32 siz, byte* fn, ...)
 		argp = (byte*)(&fn+2);  // skip caller's saved LR
 	else
 		argp = (byte*)(&fn+1);
-	runtime·newproc1(fn, argp, siz, 0);
+	runtime·newproc1(fn, argp, siz, 0, runtime·getcallerpc(&siz));
 }
 
 G*
-runtime·newproc1(byte *fn, byte *argp, int32 narg, int32 nret)
+runtime·newproc1(byte *fn, byte *argp, int32 narg, int32 nret, void *callerpc)
 {
 	byte *sp;
 	G *newg;
@@ -926,6 +926,7 @@ runtime·newproc1(byte *fn, byte *argp, int32 narg, int32 nret)
 	newg->sched.pc = (byte*)runtime·goexit;
 	newg->sched.g = newg;
 	newg->entry = fn;
+	newg->gopc = (uintptr)callerpc;
 
 	runtime·sched.gcount++;
 	runtime·goidgen++;

src/pkg/runtime/runtime.h

@@ -202,6 +202,7 @@ struct	G
 	uintptr	sigcode0;
 	uintptr	sigcode1;
 	uintptr	sigpc;
+	uintptr	gopc;	// pc of go statement that created this goroutine
 };
 struct	M
 {
@@ -452,7 +453,7 @@ void	runtime·entersyscall(void);
 void	runtime·exitsyscall(void);
 void	runtime·startcgocallback(G*);
 void	runtime·endcgocallback(G*);
-G*	runtime·newproc1(byte*, byte*, int32, int32);
+G*	runtime·newproc1(byte*, byte*, int32, int32, void*);
 void	runtime·siginit(void);
 bool	runtime·sigsend(int32 sig);
 void	runtime·gettime(int64*, int32*);