1 files changed, 307 insertions, 0 deletions
diff --git a/src/runtime/debug_test.go b/src/runtime/debug_test.go
new file mode 100644
index 0000000..1c00d2f
--- /dev/null
+++ b/src/runtime/debug_test.go
@@ -0,0 +1,307 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TODO: This test could be implemented on all (most?) UNIXes if we
+// added syscall.Tgkill more widely.
+
+// We skip all of these tests under race mode because our test thread
+// spends all of its time in the race runtime, which isn't a safe
+// point.
+
+//go:build (amd64 || arm64 || ppc64le) && linux && !race
+
+package runtime_test
+
+import (
+	"fmt"
+	"internal/abi"
+	"math"
+	"os"
+	"regexp"
+	"runtime"
+	"runtime/debug"
+	"sync/atomic"
+	"syscall"
+	"testing"
+)
+
+func startDebugCallWorker(t *testing.T) (g *runtime.G, after func()) {
+	// This can deadlock if run under a debugger because it
+	// depends on catching SIGTRAP, which is usually swallowed by
+	// a debugger.
+	skipUnderDebugger(t)
+
+	// This can deadlock if there aren't enough threads or if a GC
+	// tries to interrupt an atomic loop (see issue #10958). Execute
+	// an extra GC to ensure even the sweep phase is done (out of
+	// caution to prevent #49370 from happening).
+	// TODO(mknyszek): This extra GC cycle is likely unnecessary
+	// because preemption (which may happen during the sweep phase)
+	// isn't much of an issue anymore thanks to asynchronous preemption.
+	// The biggest risk is having a write barrier in the debug call
+	// injection test code fire, because it runs in a signal handler
+	// and may not have a P.
+	//
+	// We use 8 Ps so there's room for the debug call worker,
+	// something that's trying to preempt the call worker, and the
+	// goroutine that's trying to stop the call worker.
+	ogomaxprocs := runtime.GOMAXPROCS(8)
+	ogcpercent := debug.SetGCPercent(-1)
+	runtime.GC()
+
+	// ready is a buffered channel so debugCallWorker won't block
+	// on sending to it. This makes it less likely we'll catch
+	// debugCallWorker while it's in the runtime.
+	ready := make(chan *runtime.G, 1)
+	var stop uint32
+	done := make(chan error)
+	go debugCallWorker(ready, &stop, done)
+	g = <-ready
+	return g, func() {
+		atomic.StoreUint32(&stop, 1)
+		err := <-done
+		if err != nil {
+			t.Fatal(err)
+		}
+		runtime.GOMAXPROCS(ogomaxprocs)
+		debug.SetGCPercent(ogcpercent)
+	}
+}
+
+func debugCallWorker(ready chan<- *runtime.G, stop *uint32, done chan<- error) {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	ready <- runtime.Getg()
+
+	x := 2
+	debugCallWorker2(stop, &x)
+	if x != 1 {
+		done <- fmt.Errorf("want x = 2, got %d; register pointer not adjusted?", x)
+	}
+	close(done)
+}
+
+// Don't inline this function, since we want to test adjusting
+// pointers in the arguments.
+//
+//go:noinline
+func debugCallWorker2(stop *uint32, x *int) {
+	for atomic.LoadUint32(stop) == 0 {
+		// Strongly encourage x to live in a register so we
+		// can test pointer register adjustment.
+		*x++
+	}
+	*x = 1
+}
+
+func debugCallTKill(tid int) error {
+	return syscall.Tgkill(syscall.Getpid(), tid, syscall.SIGTRAP)
+}
+
+// skipUnderDebugger skips the current test when running under a
+// debugger (specifically if this process has a tracer). This is
+// Linux-specific.
+func skipUnderDebugger(t *testing.T) {
+	pid := syscall.Getpid()
+	status, err := os.ReadFile(fmt.Sprintf("/proc/%d/status", pid))
+	if err != nil {
+		t.Logf("couldn't get proc tracer: %s", err)
+		return
+	}
+	re := regexp.MustCompile(`TracerPid:\s+([0-9]+)`)
+	sub := re.FindSubmatch(status)
+	if sub == nil {
+		t.Logf("couldn't find proc tracer PID")
+		return
+	}
+	if string(sub[1]) == "0" {
+		return
+	}
+	t.Skip("test will deadlock under a debugger")
+}
+
+func TestDebugCall(t *testing.T) {
+	g, after := startDebugCallWorker(t)
+	defer after()
+
+	type stackArgs struct {
+		x0    int
+		x1    float64
+		y0Ret int
+		y1Ret float64
+	}
+
+	// Inject a call into the debugCallWorker goroutine and test
+	// basic argument and result passing.
+	fn := func(x int, y float64) (y0Ret int, y1Ret float64) {
+		return x + 1, y + 1.0
+	}
+	var args *stackArgs
+	var regs abi.RegArgs
+	intRegs := regs.Ints[:]
+	floatRegs := regs.Floats[:]
+	fval := float64(42.0)
+	if len(intRegs) > 0 {
+		intRegs[0] = 42
+		floatRegs[0] = math.Float64bits(fval)
+	} else {
+		args = &stackArgs{
+			x0: 42,
+			x1: 42.0,
+		}
+	}
+
+	if _, err := runtime.InjectDebugCall(g, fn, &regs, args, debugCallTKill, false); err != nil {
+		t.Fatal(err)
+	}
+	var result0 int
+	var result1 float64
+	if len(intRegs) > 0 {
+		result0 = int(intRegs[0])
+		result1 = math.Float64frombits(floatRegs[0])
+	} else {
+		result0 = args.y0Ret
+		result1 = args.y1Ret
+	}
+	if result0 != 43 {
+		t.Errorf("want 43, got %d", result0)
+	}
+	if result1 != fval+1 {
+		t.Errorf("want 43, got %f", result1)
+	}
+}
+
+func TestDebugCallLarge(t *testing.T) {
+	g, after := startDebugCallWorker(t)
+	defer after()
+
+	// Inject a call with a large call frame.
+	const N = 128
+	var args struct {
+		in  [N]int
+		out [N]int
+	}
+	fn := func(in [N]int) (out [N]int) {
+		for i := range in {
+			out[i] = in[i] + 1
+		}
+		return
+	}
+	var want [N]int
+	for i := range args.in {
+		args.in[i] = i
+		want[i] = i + 1
+	}
+	if _, err := runtime.InjectDebugCall(g, fn, nil, &args, debugCallTKill, false); err != nil {
+		t.Fatal(err)
+	}
+	if want != args.out {
+		t.Fatalf("want %v, got %v", want, args.out)
+	}
+}
+
+func TestDebugCallGC(t *testing.T) {
+	g, after := startDebugCallWorker(t)
+	defer after()
+
+	// Inject a call that performs a GC.
+	if _, err := runtime.InjectDebugCall(g, runtime.GC, nil, nil, debugCallTKill, false); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestDebugCallGrowStack(t *testing.T) {
+	g, after := startDebugCallWorker(t)
+	defer after()
+
+	// Inject a call that grows the stack. debugCallWorker checks
+	// for stack pointer breakage.
+	if _, err := runtime.InjectDebugCall(g, func() { growStack(nil) }, nil, nil, debugCallTKill, false); err != nil {
+		t.Fatal(err)
+	}
+}
+
+//go:nosplit
+func debugCallUnsafePointWorker(gpp **runtime.G, ready, stop *uint32) {
+	// The nosplit causes this function to not contain safe-points
+	// except at calls.
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	*gpp = runtime.Getg()
+
+	for atomic.LoadUint32(stop) == 0 {
+		atomic.StoreUint32(ready, 1)
+	}
+}
+
+func TestDebugCallUnsafePoint(t *testing.T) {
+	skipUnderDebugger(t)
+
+	// This can deadlock if there aren't enough threads or if a GC
+	// tries to interrupt an atomic loop (see issue #10958).
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(8))
+
+	// InjectDebugCall cannot be executed while a GC is actively in
+	// progress. Wait until the current GC is done, and turn it off.
+	//
+	// See #49370.
+	runtime.GC()
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+
+	// Test that the runtime refuses call injection at unsafe points.
+	var g *runtime.G
+	var ready, stop uint32
+	defer atomic.StoreUint32(&stop, 1)
+	go debugCallUnsafePointWorker(&g, &ready, &stop)
+	for atomic.LoadUint32(&ready) == 0 {
+		runtime.Gosched()
+	}
+
+	_, err := runtime.InjectDebugCall(g, func() {}, nil, nil, debugCallTKill, true)
+	if msg := "call not at safe point"; err == nil || err.Error() != msg {
+		t.Fatalf("want %q, got %s", msg, err)
+	}
+}
+
+func TestDebugCallPanic(t *testing.T) {
+	skipUnderDebugger(t)
+
+	// This can deadlock if there aren't enough threads.
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(8))
+
+	// InjectDebugCall cannot be executed while a GC is actively in
+	// progress. Wait until the current GC is done, and turn it off.
+	//
+	// See #10958 and #49370.
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	// TODO(mknyszek): This extra GC cycle is likely unnecessary
+	// because preemption (which may happen during the sweep phase)
+	// isn't much of an issue anymore thanks to asynchronous preemption.
+	// The biggest risk is having a write barrier in the debug call
+	// injection test code fire, because it runs in a signal handler
+	// and may not have a P.
+	runtime.GC()
+
+	ready := make(chan *runtime.G)
+	var stop uint32
+	defer atomic.StoreUint32(&stop, 1)
+	go func() {
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		ready <- runtime.Getg()
+		for atomic.LoadUint32(&stop) == 0 {
+		}
+	}()
+	g := <-ready
+
+	p, err := runtime.InjectDebugCall(g, func() { panic("test") }, nil, nil, debugCallTKill, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if ps, ok := p.(string); !ok || ps != "test" {
+		t.Fatalf("wanted panic %v, got %v", "test", p)
+	}
+}