syscall: implement syscall.Getppid() on Windows

Also added a test to verify os.Getppid() works across all platforms

LGTM=alex.brainman
R=golang-codereviews, alex.brainman, shreveal, iant
CC=golang-codereviews
https://golang.org/cl/102320044

src/pkg/os/os_test.go

@@ -1293,6 +1293,32 @@ func TestKillStartProcess(t *testing.T) {
 	})
 }
 
+func TestGetppid(t *testing.T) {
+	if runtime.GOOS == "nacl" {
+		t.Skip("skipping on nacl")
+	}
+
+	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
+		fmt.Print(Getppid())
+		Exit(0)
+	}
+
+	cmd := osexec.Command(Args[0], "-test.run=TestGetppid")
+	cmd.Env = append(Environ(), "GO_WANT_HELPER_PROCESS=1")
+
+	// verify that Getppid() from the forked process reports our process id
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
+	}
+
+	childPpid := string(output)
+	ourPid := fmt.Sprintf("%d", Getpid())
+	if childPpid != ourPid {
+		t.Fatalf("Child process reports parent process id '%v', expected '%v'", childPpid, ourPid)
+	}
+}
+
 func TestKillFindProcess(t *testing.T) {
 	testKillProcess(t, func(p *Process) {
 		p2, err := FindProcess(p.Pid)

src/pkg/syscall/syscall_windows.go

@@ -204,6 +204,9 @@ func NewCallbackCDecl(fn interface{}) uintptr
 //sys	GetConsoleMode(console Handle, mode *uint32) (err error) = kernel32.GetConsoleMode
 //sys	WriteConsole(console Handle, buf *uint16, towrite uint32, written *uint32, reserved *byte) (err error) = kernel32.WriteConsoleW
 //sys	ReadConsole(console Handle, buf *uint16, toread uint32, read *uint32, inputControl *byte) (err error) = kernel32.ReadConsoleW
+//sys	CreateToolhelp32Snapshot(flags uint32, processId uint32) (handle Handle, err error) [failretval==InvalidHandle] = kernel32.CreateToolhelp32Snapshot
+//sys	Process32First(snapshot Handle, procEntry *ProcessEntry32) (err error) = kernel32.Process32FirstW
+//sys	Process32Next(snapshot Handle, procEntry *ProcessEntry32) (err error) = kernel32.Process32NextW
 
 // syscall interface implementation for other packages
 
@@ -902,9 +905,37 @@ func FindNextFile(handle Handle, data *Win32finddata) (err error) {
 	return
 }
 
-// TODO(brainman): fix all needed for os
-func Getppid() (ppid int) { return -1 }
+func getProcessEntry(pid int) (*ProcessEntry32, error) {
+	snapshot, err := CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer CloseHandle(snapshot)
+	var procEntry ProcessEntry32
+	procEntry.Size = uint32(unsafe.Sizeof(procEntry))
+	if err = Process32First(snapshot, &procEntry); err != nil {
+		return nil, err
+	}
+	for {
+		if procEntry.ProcessID == uint32(pid) {
+			return &procEntry, nil
+		}
+		err = Process32Next(snapshot, &procEntry)
+		if err != nil {
+			return nil, err
+		}
+	}
+}
+
+func Getppid() (ppid int) {
+	pe, err := getProcessEntry(Getpid())
+	if err != nil {
+		return -1
+	}
+	return int(pe.ParentProcessID)
+}
 
+// TODO(brainman): fix all needed for os
 func Fchdir(fd Handle) (err error)                        { return EWINDOWS }
 func Link(oldpath, newpath string) (err error)            { return EWINDOWS }
 func Symlink(path, link string) (err error)               { return EWINDOWS }

src/pkg/syscall/zsyscall_windows_386.go

@@ -108,6 +108,9 @@ var (
 	procGetConsoleMode                     = modkernel32.NewProc("GetConsoleMode")
 	procWriteConsoleW                      = modkernel32.NewProc("WriteConsoleW")
 	procReadConsoleW                       = modkernel32.NewProc("ReadConsoleW")
+	procCreateToolhelp32Snapshot           = modkernel32.NewProc("CreateToolhelp32Snapshot")
+	procProcess32FirstW                    = modkernel32.NewProc("Process32FirstW")
+	procProcess32NextW                     = modkernel32.NewProc("Process32NextW")
 	procWSAStartup                         = modws2_32.NewProc("WSAStartup")
 	procWSACleanup                         = modws2_32.NewProc("WSACleanup")
 	procWSAIoctl                           = modws2_32.NewProc("WSAIoctl")
@@ -1254,6 +1257,43 @@ func ReadConsole(console Handle, buf *uint16, toread uint32, read *uint32, input
 	return
 }
 
+func CreateToolhelp32Snapshot(flags uint32, processId uint32) (handle Handle, err error) {
+	r0, _, e1 := Syscall(procCreateToolhelp32Snapshot.Addr(), 2, uintptr(flags), uintptr(processId), 0)
+	handle = Handle(r0)
+	if handle == InvalidHandle {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
+func Process32First(snapshot Handle, procEntry *ProcessEntry32) (err error) {
+	r1, _, e1 := Syscall(procProcess32FirstW.Addr(), 2, uintptr(snapshot), uintptr(unsafe.Pointer(procEntry)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
+func Process32Next(snapshot Handle, procEntry *ProcessEntry32) (err error) {
+	r1, _, e1 := Syscall(procProcess32NextW.Addr(), 2, uintptr(snapshot), uintptr(unsafe.Pointer(procEntry)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
 func WSAStartup(verreq uint32, data *WSAData) (sockerr error) {
 	r0, _, _ := Syscall(procWSAStartup.Addr(), 2, uintptr(verreq), uintptr(unsafe.Pointer(data)), 0)
 	if r0 != 0 {

src/pkg/syscall/zsyscall_windows_amd64.go

@@ -108,6 +108,9 @@ var (
 	procGetConsoleMode                     = modkernel32.NewProc("GetConsoleMode")
 	procWriteConsoleW                      = modkernel32.NewProc("WriteConsoleW")
 	procReadConsoleW                       = modkernel32.NewProc("ReadConsoleW")
+	procCreateToolhelp32Snapshot           = modkernel32.NewProc("CreateToolhelp32Snapshot")
+	procProcess32FirstW                    = modkernel32.NewProc("Process32FirstW")
+	procProcess32NextW                     = modkernel32.NewProc("Process32NextW")
 	procWSAStartup                         = modws2_32.NewProc("WSAStartup")
 	procWSACleanup                         = modws2_32.NewProc("WSACleanup")
 	procWSAIoctl                           = modws2_32.NewProc("WSAIoctl")
@@ -1254,6 +1257,43 @@ func ReadConsole(console Handle, buf *uint16, toread uint32, read *uint32, input
 	return
 }
 
+func CreateToolhelp32Snapshot(flags uint32, processId uint32) (handle Handle, err error) {
+	r0, _, e1 := Syscall(procCreateToolhelp32Snapshot.Addr(), 2, uintptr(flags), uintptr(processId), 0)
+	handle = Handle(r0)
+	if handle == InvalidHandle {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
+func Process32First(snapshot Handle, procEntry *ProcessEntry32) (err error) {
+	r1, _, e1 := Syscall(procProcess32FirstW.Addr(), 2, uintptr(snapshot), uintptr(unsafe.Pointer(procEntry)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
+func Process32Next(snapshot Handle, procEntry *ProcessEntry32) (err error) {
+	r1, _, e1 := Syscall(procProcess32NextW.Addr(), 2, uintptr(snapshot), uintptr(unsafe.Pointer(procEntry)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = EINVAL
+		}
+	}
+	return
+}
+
 func WSAStartup(verreq uint32, data *WSAData) (sockerr error) {
 	r0, _, _ := Syscall(procWSAStartup.Addr(), 2, uintptr(verreq), uintptr(unsafe.Pointer(data)), 0)
 	if r0 != 0 {

src/pkg/syscall/ztypes_windows.go

@@ -175,6 +175,17 @@ const (
 	CTRL_BREAK_EVENT = 1
 )
 
+const (
+	// flags for CreateToolhelp32Snapshot
+	TH32CS_SNAPHEAPLIST = 0x01
+	TH32CS_SNAPPROCESS  = 0x02
+	TH32CS_SNAPTHREAD   = 0x04
+	TH32CS_SNAPMODULE   = 0x08
+	TH32CS_SNAPMODULE32 = 0x10
+	TH32CS_SNAPALL      = TH32CS_SNAPHEAPLIST | TH32CS_SNAPMODULE | TH32CS_SNAPPROCESS | TH32CS_SNAPTHREAD
+	TH32CS_INHERIT      = 0x80000000
+)
+
 const (
 	// do not reorder
 	FILE_NOTIFY_CHANGE_FILE_NAME = 1 << iota
@@ -462,6 +473,19 @@ type ProcessInformation struct {
 	ThreadId  uint32
 }
 
+type ProcessEntry32 struct {
+	Size            uint32
+	Usage           uint32
+	ProcessID       uint32
+	DefaultHeapID   uintptr
+	ModuleID        uint32
+	Threads         uint32
+	ParentProcessID uint32
+	PriClassBase    int32
+	Flags           uint32
+	ExeFile         [MAX_PATH]uint16
+}
+
 type Systemtime struct {
 	Year         uint16
 	Month        uint16