Can we call Native Windows API from Delphi?

Question

Is it possible to call the kernel Native APIs from within a Delphi application? Like nt and zw syscalls.

Answer 1

You can indeed call the native API from Delphi.

Delphi does not ship with header translations for the native API. So you need to provide your own, or use a pre-existing translation. For example. the JEDI translation of the NT API.

Answer 2

As David Heffernan says it's perfectly possible to use the Native API from usermode and thus Delphi. You will need the JwaNative unit from the Jedi Apilib.

Here is small example to enumerate processes using the Native API: (TProcessList is a descendant from TObjectList but the relevant part is the call to NtQuerySystemInformation)

function EnumProcesses: TProcessList;
var
  Current: PSystemProcesses;
  SystemProcesses : PSystemProcesses;
  dwSize: DWORD;
  nts: NTSTATUS;
begin
  Result := TProcessList.Create;

  dwSize := 200000;
  SystemProcesses := AllocMem(dwSize);

  nts := NtQuerySystemInformation(SystemProcessesAndThreadsInformation,
      SystemProcesses, dwSize, @dwSize);

  while nts = STATUS_INFO_LENGTH_MISMATCH do
  begin
    ReAllocMem(SystemProcesses, dwSize);
    nts := NtQuerySystemInformation(SystemProcessesAndThreadsInformation,
      SystemProcesses, dwSize, @dwSize);
  end;

  if nts = STATUS_SUCCESS then
  begin
    Current := SystemProcesses;
    while True do
    begin
      Result.Add(TProcess.Create(Current^));
      if Current^.NextEntryDelta = 0 then
        Break;

      Current := PSYSTEM_PROCESSES(DWORD_PTR(Current) + Current^.NextEntryDelta);
    end;
  end;

  FreeMem(SystemProcesses);
end;