;@echo off
;goto make

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
;
; Global Descriptor Table Dumper.
;
; Written by Four-F (four-f@mail.ru)
;
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

.386
.model flat, stdcall
option casemap:none

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;                                  I N C L U D E   F I L E S                                        
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

include \masm32\include\w2k\ntstatus.inc
include \masm32\include\w2k\ntddk.inc

include \masm32\include\w2k\ntoskrnl.inc

includelib \masm32\lib\w2k\ntoskrnl.lib

include \masm32\Macros\Strings.mac

include ..\common.inc
;include seh0.inc


XDT STRUC
	Limit	WORD	?
	Base	DWORD	?
XDT ENDS
  
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
;                                     C O N S T A N T S                                             
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

.const
CCOUNTED_UNICODE_STRING	"\\Device\\GdtDump", g_usDeviceName, 4
CCOUNTED_UNICODE_STRING	"\\DosDevices\\GdtDump", g_usSymbolicLinkName, 4

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
;                            N O N D I S C A R D A B L E   C O D E                                  
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

.code

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
;                                   DispatchCreateClose                                             
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

DispatchCreateClose proc pDeviceObject:PDEVICE_OBJECT, pIrp:PIRP

	mov eax, pIrp
	mov (_IRP PTR [eax]).IoStatus.Status, STATUS_SUCCESS
	and (_IRP PTR [eax]).IoStatus.Information, 0

	fastcall IofCompleteRequest, pIrp, IO_NO_INCREMENT

	mov eax, STATUS_SUCCESS
	ret

DispatchCreateClose endp

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
;                                     DispatchControl                                               
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

DispatchControl proc uses esi edi pDeviceObject:PDEVICE_OBJECT, pIrp:PIRP

local dwContext:DWORD
local gdt:XDT
local padding:WORD		; padding for next local if any

	mov esi, pIrp
	assume esi:ptr _IRP

	mov [esi].IoStatus.Status, STATUS_UNSUCCESSFUL
	and [esi].IoStatus.Information, 0

	IoGetCurrentIrpStackLocation esi
	mov edi, eax
	assume edi:ptr IO_STACK_LOCATION

	.if [edi].Parameters.DeviceIoControl.IoControlCode == IOCTL_DUMP_GDT
		.if [edi].Parameters.DeviceIoControl.OutputBufferLength >= BUFFER_SIZE

			sgdt gdt
			movzx eax, gdt.Limit
			; first two DWORD will be Gdt.Base and Gdt.Limit
			.if eax <= BUFFER_SIZE - sizeof DWORD * 2

				mov ecx, [esi].AssociatedIrp.SystemBuffer

				mov eax, gdt.Base
				mov [ecx], eax

				movzx eax, gdt.Limit
				mov [ecx][4], eax

				add ecx, sizeof DWORD * 2
				invoke memcpy, ecx, gdt.Base, eax

				movzx eax, gdt.Limit
				; The GDT limit is always be one less than an integral multiple of eight (that is, 8N