src/runtime/debug_test.go - go - Git at Google

 // 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.

 // +build amd64
 // +build linux
 // +build !race

 package runtime_test

 import (
 	"fmt"
 	"io/ioutil"
 	"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). 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)

 	// 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 := ioutil.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()

 	// Inject a call into the debugCallWorker goroutine and test
 	// basic argument and result passing.
 	var args struct {
 		x    int
 		yRet int
 	}
 	fn := func(x int) (yRet int) {
 		return x + 1
 	}
 	args.x = 42
 	if _, err := runtime.InjectDebugCall(g, fn, &args, debugCallTKill); err != nil {
 		t.Fatal(err)
 	}
 	if args.yRet != 43 {
 		t.Fatalf("want 43, got %d", args.yRet)
 	}
 }

 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, &args, debugCallTKill); 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, debugCallTKill); 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, debugCallTKill); 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))
 	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, debugCallTKill)
 	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))

 	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, debugCallTKill)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if ps, ok := p.(string); !ok || ps != "test" {
 		t.Fatalf("wanted panic %v, got %v", "test", p)
 	}
 }
	// 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.

	// +build amd64
	// +build linux
	// +build !race

	package runtime_test

	import (
	"fmt"
	"io/ioutil"
	"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). 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)

	// 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 := ioutil.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()

	// Inject a call into the debugCallWorker goroutine and test
	// basic argument and result passing.
	var args struct {
	x int
	yRet int
	}
	fn := func(x int) (yRet int) {
	return x + 1
	}
	args.x = 42
	if _, err := runtime.InjectDebugCall(g, fn, &args, debugCallTKill); err != nil {
	t.Fatal(err)
	}
	if args.yRet != 43 {
	t.Fatalf("want 43, got %d", args.yRet)
	}
	}

	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, &args, debugCallTKill); 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, debugCallTKill); 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, debugCallTKill); 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))
	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, debugCallTKill)
	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))

	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, debugCallTKill)
	if err != nil {
	t.Fatal(err)
	}
	if ps, ok := p.(string); !ok \|\| ps != "test" {
	t.Fatalf("wanted panic %v, got %v", "test", p)
	}
	}