runtime: fix getcallerpc args

Change-Id: I6b14b8eecf125dd74bd40f4e7fff6b49de150e42
Reviewed-on: https://go-review.googlesource.com/19897
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/runtime/race/output_test.go

@@ -180,4 +180,21 @@ func TestFail(t *testing.T) {
 PASS
 Found 1 data race\(s\)
 FAIL`},
+
+	{"slicebytetostring_pc", "run", "atexit_sleep_ms=0", `
+package main
+func main() {
+	done := make(chan string)
+	data := make([]byte, 10)
+	go func() {
+		done <- string(data)
+	}()
+	data[0] = 1
+	<-done
+}
+`, `
+  runtime\.slicebytetostring\(\)
+      .*/runtime/string\.go:.*
+  main\.main\.func1\(\)
+      .*/main.go:7`},
 }

src/runtime/string.go

@@ -84,7 +84,7 @@ func slicebytetostring(buf *tmpBuf, b []byte) string {
 	if raceenabled && l > 0 {
 		racereadrangepc(unsafe.Pointer(&b[0]),
 			uintptr(l),
-			getcallerpc(unsafe.Pointer(&b)),
+			getcallerpc(unsafe.Pointer(&buf)),
 			funcPC(slicebytetostring))
 	}
 	if msanenabled && l > 0 {
@@ -189,7 +189,7 @@ func slicerunetostring(buf *tmpBuf, a []rune) string {
 	if raceenabled && len(a) > 0 {
 		racereadrangepc(unsafe.Pointer(&a[0]),
 			uintptr(len(a))*unsafe.Sizeof(a[0]),
-			getcallerpc(unsafe.Pointer(&a)),
+			getcallerpc(unsafe.Pointer(&buf)),
 			funcPC(slicerunetostring))
 	}
 	if msanenabled && len(a) > 0 {