windows: do not return invalid error for psuedo-handle functions

GetCurrentProcess and GetCurrentThread return -1 and -2 respectively. We
could arguably hard code those values, but MSDN cautions not to; I'm
sure this advice is old now, given that the psuedo handles for tokens
(not processes/threads) are now implemented with inline functions in the
headers for Windows 8, but anyway, we'll follow Microsoft's advice.
However, regardless of that, these functions never ever return an error.
MSDN doesn't indicate that they do, reverse engineering the functions
doesn't indicate that they do, and checking against 0 is just plain
wrong, considering 0!=INVALID_HANDLE_VALUE; however
INVALID_HANDLE_VALUE==-1, so that's not correct either. In fact,
checking any value and returning any error does not make sense.
Incidently having to check code for the pseudo handle is more verbose
too.

In order to make this function do the correct thing and meet the spec,
remove the error value from the return.

Change-Id: If03c9dab001be3bf5a04999aef20dbfcf8a4f405
Reviewed-on: https://go-review.googlesource.com/c/sys/+/196798
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

windows/security_windows.go

@@ -652,17 +652,9 @@ type Token Handle
 // associated with current process. It is a real
 // token that needs to be closed, unlike
 // GetCurrentProcessToken.
-func OpenCurrentProcessToken() (Token, error) {
-	p, e := GetCurrentProcess()
-	if e != nil {
-		return 0, e
-	}
-	var t Token
-	e = OpenProcessToken(p, TOKEN_QUERY|TOKEN_DUPLICATE, &t)
-	if e != nil {
-		return 0, e
-	}
-	return t, nil
+func OpenCurrentProcessToken() (token Token, err error) {
+	err = OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY|TOKEN_DUPLICATE, &token)
+	return
 }
 
 // GetCurrentProcessToken returns the access token associated with

windows/syscall_windows.go

@@ -178,8 +178,8 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	TerminateProcess(handle Handle, exitcode uint32) (err error)
 //sys	GetExitCodeProcess(handle Handle, exitcode *uint32) (err error)
 //sys	GetStartupInfo(startupInfo *StartupInfo) (err error) = GetStartupInfoW
-//sys	GetCurrentProcess() (pseudoHandle Handle, err error)
-//sys	GetCurrentThread() (pseudoHandle Handle, err error)
+//sys	GetCurrentProcess() (pseudoHandle Handle)
+//sys	GetCurrentThread() (pseudoHandle Handle)
 //sys	GetProcessTimes(handle Handle, creationTime *Filetime, exitTime *Filetime, kernelTime *Filetime, userTime *Filetime) (err error)
 //sys	DuplicateHandle(hSourceProcessHandle Handle, hSourceHandle Handle, hTargetProcessHandle Handle, lpTargetHandle *Handle, dwDesiredAccess uint32, bInheritHandle bool, dwOptions uint32) (err error)
 //sys	WaitForSingleObject(handle Handle, waitMilliseconds uint32) (event uint32, err error) [failretval==0xffffffff]

windows/syscall_windows_test.go

@@ -250,8 +250,7 @@ func TestGetNamedSecurityInfo(t *testing.T) {
 }
 
 func TestGetSecurityInfo(t *testing.T) {
-	process, _ := windows.GetCurrentProcess()
-	sd, err := windows.GetSecurityInfo(process, windows.SE_KERNEL_OBJECT, windows.DACL_SECURITY_INFORMATION)
+	sd, err := windows.GetSecurityInfo(windows.GetCurrentProcess(), windows.SE_KERNEL_OBJECT, windows.DACL_SECURITY_INFORMATION)
 	if err != nil {
 		t.Fatal(err)
 	}

windows/zsyscall_windows.go

@@ -1209,29 +1209,15 @@ func GetStartupInfo(startupInfo *StartupInfo) (err error) {
 	return
 }
 
-func GetCurrentProcess() (pseudoHandle Handle, err error) {
-	r0, _, e1 := syscall.Syscall(procGetCurrentProcess.Addr(), 0, 0, 0, 0)
+func GetCurrentProcess() (pseudoHandle Handle) {
+	r0, _, _ := syscall.Syscall(procGetCurrentProcess.Addr(), 0, 0, 0, 0)
 	pseudoHandle = Handle(r0)
-	if pseudoHandle == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
-	}
 	return
 }
 
-func GetCurrentThread() (pseudoHandle Handle, err error) {
-	r0, _, e1 := syscall.Syscall(procGetCurrentThread.Addr(), 0, 0, 0, 0)
+func GetCurrentThread() (pseudoHandle Handle) {
+	r0, _, _ := syscall.Syscall(procGetCurrentThread.Addr(), 0, 0, 0, 0)
 	pseudoHandle = Handle(r0)
-	if pseudoHandle == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
-	}
 	return
 }