windows: add definitions and functions for ProcThreadAttributeList

The bulk of the documentation for these is in:

https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-updateprocthreadattribute

This allows creating processes from scratch that use advanced options,
such as changing the process parent.

Fixes golang/go#44005.

Change-Id: Id5cc5400541e57710b9e888cd37ef4f925d510fe
Reviewed-on: https://go-review.googlesource.com/c/sys/+/288412
Trust: Jason A. Donenfeld <[email protected]>
Trust: Alex Brainman <[email protected]>
Run-TryBot: Jason A. Donenfeld <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Alex Brainman <[email protected]>

Author: zx2c4

windows/exec_windows.go

@@ -6,6 +6,11 @@
 
 package windows
 
+import (
+	errorspkg "errors"
+	"unsafe"
+)
+
 // EscapeArg rewrites command line argument s as prescribed
 // in http://msdn.microsoft.com/en-us/library/ms880421.
 // This function returns "" (2 double quotes) if s is empty.
@@ -95,3 +100,31 @@ func FullPath(name string) (path string, err error) {
 		}
 	}
 }
+
+// NewProcThreadAttributeList allocates a new ProcThreadAttributeList, with the requested maximum number of attributes.
+func NewProcThreadAttributeList(maxAttrCount uint32) (*ProcThreadAttributeList, error) {
+	var size uintptr
+	err := initializeProcThreadAttributeList(nil, maxAttrCount, 0, &size)
+	if err != ERROR_INSUFFICIENT_BUFFER {
+		if err == nil {
+			return nil, errorspkg.New("unable to query buffer size from InitializeProcThreadAttributeList")
+		}
+		return nil, err
+	}
+	al := (*ProcThreadAttributeList)(unsafe.Pointer(&make([]byte, size)[0]))
+	err = initializeProcThreadAttributeList(al, maxAttrCount, 0, &size)
+	if err != nil {
+		return nil, err
+	}
+	return al, err
+}
+
+// Update modifies the ProcThreadAttributeList using UpdateProcThreadAttribute.
+func (al *ProcThreadAttributeList) Update(attribute uintptr, flags uint32, value unsafe.Pointer, size uintptr, prevValue uintptr, returnedSize *uintptr) error {
+	return updateProcThreadAttribute(al, flags, attribute, uintptr(value), size, prevValue, returnedSize)
+}
+
+// Delete frees ProcThreadAttributeList's resources.
+func (al *ProcThreadAttributeList) Delete() {
+	deleteProcThreadAttributeList(al)
+}

windows/syscall_windows.go

@@ -214,6 +214,9 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	CancelIo(s Handle) (err error)
 //sys	CancelIoEx(s Handle, o *Overlapped) (err error)
 //sys	CreateProcess(appName *uint16, commandLine *uint16, procSecurity *SecurityAttributes, threadSecurity *SecurityAttributes, inheritHandles bool, creationFlags uint32, env *uint16, currentDir *uint16, startupInfo *StartupInfo, outProcInfo *ProcessInformation) (err error) = CreateProcessW
+//sys   initializeProcThreadAttributeList(attrlist *ProcThreadAttributeList, attrcount uint32, flags uint32, size *uintptr) (err error) = InitializeProcThreadAttributeList
+//sys   deleteProcThreadAttributeList(attrlist *ProcThreadAttributeList) = DeleteProcThreadAttributeList
+//sys   updateProcThreadAttribute(attrlist *ProcThreadAttributeList, flags uint32, attr uintptr, value uintptr, size uintptr, prevvalue uintptr, returnedsize *uintptr) (err error) = UpdateProcThreadAttribute
 //sys	OpenProcess(desiredAccess uint32, inheritHandle bool, processId uint32) (handle Handle, err error)
 //sys	ShellExecute(hwnd Handle, verb *uint16, file *uint16, args *uint16, cwd *uint16, showCmd int32) (err error) [failretval<=32] = shell32.ShellExecuteW
 //sys	GetWindowThreadProcessId(hwnd HWND, pid *uint32) (tid uint32, err error) = user32.GetWindowThreadProcessId

windows/types_windows.go

@@ -215,6 +215,18 @@ const (
 	INHERIT_PARENT_AFFINITY          = 0x00010000
 )
 
+const (
+	// attributes for ProcThreadAttributeList
+	PROC_THREAD_ATTRIBUTE_PARENT_PROCESS    = 0x00020000
+	PROC_THREAD_ATTRIBUTE_HANDLE_LIST       = 0x00020002
+	PROC_THREAD_ATTRIBUTE_GROUP_AFFINITY    = 0x00030003
+	PROC_THREAD_ATTRIBUTE_PREFERRED_NODE    = 0x00020004
+	PROC_THREAD_ATTRIBUTE_IDEAL_PROCESSOR   = 0x00030005
+	PROC_THREAD_ATTRIBUTE_MITIGATION_POLICY = 0x00020007
+	PROC_THREAD_ATTRIBUTE_UMS_THREAD        = 0x00030006
+	PROC_THREAD_ATTRIBUTE_PROTECTION_LEVEL  = 0x0002000b
+)
+
 const (
 	// flags for CreateToolhelp32Snapshot
 	TH32CS_SNAPHEAPLIST = 0x01
@@ -886,6 +898,19 @@ type StartupInfo struct {
 	StdErr        Handle
 }
 
+type StartupInfoEx struct {
+	StartupInfo
+	ProcThreadAttributeList *ProcThreadAttributeList
+}
+
+// ProcThreadAttributeList is a placeholder type to represent a PROC_THREAD_ATTRIBUTE_LIST.
+//
+// To create a *ProcThreadAttributeList, use NewProcThreadAttributeList, and
+// free its memory using ProcThreadAttributeList.Delete.
+type ProcThreadAttributeList struct {
+	_ [1]byte
+}
+
 type ProcessInformation struct {
 	Process   Handle
 	Thread    Handle