pkg/system: rewrite IsWindowsClient() using golang.org/x/sys/windows

Looks like we should be able to use the implementation from x/sys/windows.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/system/syscall_windows.go

@@ -1,10 +1,6 @@
 package system // import "github.com/docker/docker/pkg/system"
 
-import (
-	"unsafe"
-
-	"github.com/sirupsen/logrus"
-)
+import "golang.org/x/sys/windows"
 
 const (
 	// Deprecated: use github.com/docker/pkg/idtools.SeTakeOwnershipPrivilege
@@ -15,35 +11,13 @@ const (
 	ContainerUserSidString = "S-1-5-93-2-2"
 )
 
-var procGetVersionExW = modkernel32.NewProc("GetVersionExW")
-
-// https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-osversioninfoexa
-// TODO: use golang.org/x/sys/windows.OsVersionInfoEx (needs OSVersionInfoSize to be exported)
-type osVersionInfoEx struct {
-	OSVersionInfoSize uint32
-	MajorVersion      uint32
-	MinorVersion      uint32
-	BuildNumber       uint32
-	PlatformID        uint32
-	CSDVersion        [128]uint16
-	ServicePackMajor  uint16
-	ServicePackMinor  uint16
-	SuiteMask         uint16
-	ProductType       byte
-	Reserve           byte
-}
+// VER_NT_WORKSTATION, see https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-osversioninfoexa
+const verNTWorkstation = 0x00000001 // VER_NT_WORKSTATION
 
 // IsWindowsClient returns true if the SKU is client. It returns false on
 // Windows server, or if an error occurred when making the GetVersionExW
 // syscall.
 func IsWindowsClient() bool {
-	osviex := &osVersionInfoEx{OSVersionInfoSize: 284}
-	r1, _, err := procGetVersionExW.Call(uintptr(unsafe.Pointer(osviex)))
-	if r1 == 0 {
-		logrus.WithError(err).Warn("GetVersionExW failed - assuming server SKU")
-		return false
-	}
-	// VER_NT_WORKSTATION, see https://docs.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-osversioninfoexa
-	const verNTWorkstation = 0x00000001 // VER_NT_WORKSTATION
-	return osviex.ProductType == verNTWorkstation
+	ver := windows.RtlGetVersion()
+	return ver != nil && ver.ProductType == verNTWorkstation
 }