diff --git a/src/run.bash b/src/run.bash
index 3c9430c87e..9a0e1cb0f2 100755
--- a/src/run.bash
+++ b/src/run.bash
@@ -70,9 +70,10 @@ case "$GOHOSTOS-$GOOS-$GOARCH-$CGO_ENABLED" in
 linux-linux-amd64-1 | freebsd-freebsd-amd64-1 | darwin-darwin-amd64-1)
 	echo
 	echo '# Testing race detector.'
-	go test -race -i runtime/race flag
+	go test -race -i runtime/race flag os/exec
 	go test -race -run=Output runtime/race
-	go test -race -short flag
+	go test -race -short flag os/exec
+	go test -race -short -ldflags=-linkmode=external flag os/exec
 esac
 
 xcd() {
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 8cf1c3d342..1170449440 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -490,6 +490,8 @@ func GC() {
 
 // linker-provided
 var noptrdata struct{}
+var enoptrdata struct{}
+var noptrbss struct{}
 var enoptrbss struct{}
 
 // SetFinalizer sets the finalizer associated with x to f.
@@ -566,8 +568,13 @@ func SetFinalizer(obj interface{}, finalizer interface{}) {
 		//	func main() {
 		//		runtime.SetFinalizer(Foo, nil)
 		//	}
-		// The segments are, in order: text, rodata, noptrdata, data, bss, noptrbss.
-		if uintptr(unsafe.Pointer(&noptrdata)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrbss)) {
+		// The relevant segments are: noptrdata, data, bss, noptrbss.
+		// We cannot assume they are in any order or even contiguous,
+		// due to external linking.
+		if uintptr(unsafe.Pointer(&noptrdata)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrdata)) ||
+			uintptr(unsafe.Pointer(&data)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&edata)) ||
+			uintptr(unsafe.Pointer(&bss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&ebss)) ||
+			uintptr(unsafe.Pointer(&noptrbss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrbss)) {
 			return
 		}
 		gothrow("runtime.SetFinalizer: pointer not in allocated block")
diff --git a/src/runtime/race.c b/src/runtime/race.c
index 9ac73fbccf..e400c8d102 100644
--- a/src/runtime/race.c
+++ b/src/runtime/race.c
@@ -63,8 +63,14 @@ void __tsan_go_ignore_sync_end(void);
 #pragma cgo_import_static __tsan_go_atomic64_compare_exchange
 
 extern byte runtime·noptrdata[];
+extern byte runtime·enoptrdata[];
+extern byte runtime·data[];
+extern byte runtime·edata[];
+extern byte runtime·bss[];
+extern byte runtime·ebss[];
+extern byte runtime·noptrbss[];
 extern byte runtime·enoptrbss[];
-  
+
 // start/end of heap for race_amd64.s
 uintptr runtime·racearenastart;
 uintptr runtime·racearenaend;
@@ -86,7 +92,13 @@ isvalidaddr(uintptr addr)
 {
 	if(addr >= runtime·racearenastart && addr < runtime·racearenaend)
 		return true;
-	if(addr >= (uintptr)runtime·noptrdata && addr < (uintptr)runtime·enoptrbss)
+	if(addr >= (uintptr)runtime·noptrdata && addr < (uintptr)runtime·enoptrdata)
+		return true;
+	if(addr >= (uintptr)runtime·data && addr < (uintptr)runtime·edata)
+		return true;
+	if(addr >= (uintptr)runtime·bss && addr < (uintptr)runtime·ebss)
+		return true;
+	if(addr >= (uintptr)runtime·noptrbss && addr < (uintptr)runtime·enoptrbss)
 		return true;
 	return false;
 }
@@ -95,15 +107,37 @@ isvalidaddr(uintptr addr)
 uintptr
 runtime·raceinit(void)
 {
-	uintptr racectx, start, size;
+	uintptr racectx, start, end, size;
 
 	// cgo is required to initialize libc, which is used by race runtime
 	if(!runtime·iscgo)
 		runtime·throw("raceinit: race build must use cgo");
 	runtime·racecall(__tsan_init, &racectx, runtime·racesymbolizethunk);
 	// Round data segment to page boundaries, because it's used in mmap().
-	start = (uintptr)runtime·noptrdata & ~(PageSize-1);
-	size = ROUND((uintptr)runtime·enoptrbss - start, PageSize);
+	// The relevant sections are noptrdata, data, bss, noptrbss.
+	// In external linking mode, there may be other non-Go data mixed in,
+	// and the sections may even occur out of order.
+	// Work out a conservative range of addresses.
+	start = ~(uintptr)0;
+	end = 0;
+	if(start > (uintptr)runtime·noptrdata)
+		start = (uintptr)runtime·noptrdata;
+	if(start > (uintptr)runtime·data)
+		start = (uintptr)runtime·data;
+	if(start > (uintptr)runtime·noptrbss)
+		start = (uintptr)runtime·noptrbss;
+	if(start > (uintptr)runtime·bss)
+		start = (uintptr)runtime·bss;
+	if(end < (uintptr)runtime·enoptrdata)
+		end = (uintptr)runtime·enoptrdata;
+	if(end < (uintptr)runtime·edata)
+		end = (uintptr)runtime·edata;
+	if(end < (uintptr)runtime·enoptrbss)
+		end = (uintptr)runtime·enoptrbss;
+	if(end < (uintptr)runtime·ebss)
+		end = (uintptr)runtime·ebss;
+	start = start & ~(PageSize-1);
+	size = ROUND(end - start, PageSize);
 	runtime·racecall(__tsan_map_shadow, start, size);
 	return racectx;
 }