Introduce containerd-shim-runhcs-v1 on Windows

Implements the containerd-shim-runhcs-v1 shim on Windows for the runtime
v2 shim API.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

runtime/v2/shim/shim_windows.go

@@ -27,6 +27,7 @@ import (
 	"os"
 	"os/exec"
 	"sync"
+	"unsafe"
 
 	winio "github.com/Microsoft/go-winio"
 	"github.com/containerd/containerd/events"
@@ -35,6 +36,7 @@ import (
 	"github.com/containerd/typeurl"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/windows"
 )
 
 // setupSignals creates a new signal handler for all signals
@@ -51,8 +53,43 @@ func subreaper() error {
 	return nil
 }
 
+type fakeSignal struct {
+}
+
+func (fs *fakeSignal) String() string {
+	return ""
+}
+
+func (fs *fakeSignal) Signal() {
+}
+
 func setupDumpStacks(dump chan<- os.Signal) {
-	// TODO: JTERRY75: Make this based on events. signal.Notify(dump, syscall.SIGUSR1)
+	// Windows does not support signals like *nix systems. So instead of
+	// trapping on SIGUSR1 to dump stacks, we wait on a Win32 event to be
+	// signaled. ACL'd to builtin administrators and local system
+	event := "Global\\containerd-shim-runhcs-v1-" + fmt.Sprint(os.Getpid())
+	ev, _ := windows.UTF16PtrFromString(event)
+	sd, err := winio.SddlToSecurityDescriptor("D:P(A;;GA;;;BA)(A;;GA;;;SY)")
+	if err != nil {
+		logrus.Errorf("failed to get security descriptor for debug stackdump event %s: %s", event, err.Error())
+		return
+	}
+	var sa windows.SecurityAttributes
+	sa.Length = uint32(unsafe.Sizeof(sa))
+	sa.InheritHandle = 1
+	sa.SecurityDescriptor = uintptr(unsafe.Pointer(&sd[0]))
+	h, err := windows.CreateEvent(&sa, 0, 0, ev)
+	if h == 0 || err != nil {
+		logrus.Errorf("failed to create debug stackdump event %s: %s", event, err.Error())
+		return
+	}
+	go func() {
+		logrus.Debugf("Stackdump - waiting signal at %s", event)
+		for {
+			windows.WaitForSingleObject(h, windows.INFINITE)
+			dump <- new(fakeSignal)
+		}
+	}()
 }
 
 // serve serves the ttrpc API over a unix socket at the provided path