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title "Processor type and stepping detection";++;; Copyright (c) 1989 Microsoft Corporation;; Module Name:;; main.asm;; Abstract:;; This file implements the main entry code for x86 hardware detection; module. This assembly file is required in order to link C modules; into a "/TINY" (single segment) memory module.;; Author:;; Shie-Lin Tzong (shielint) 15-Feb-1992.; The code is extracted from NTLDR su.asm.;; Environment:;; x86 Real Mode.;; Revision History:;;; Build Notes:; ~~~~~~~~~~~~; The microsoft C compiler will not produce "tiny" model programs. In the; tiny model, the entire program consists of only one segment. The small; model produced by our compilers consists of two segments: DGROUP and _TEXT.; If you convert a small model program into a tiny model program, DS (which; should point to DGROUP (bss,const,data) will always be wrong. For this reason; we need an assembly module to do a simple run-time fixup on SS and DS. To; guarantee that DS will point to DGROUP no matter where the detection module; is loaded, the paragraph (shifted right four bits) offset of DGROUP from; _TEXT must be added to the value in CS to compute DS and SS.;; We get the linker to fixup the offset of the beginning of the dgroup segment; relative to the beginning of the code segment and it's this value added; to the value in CS that allows us to build a "tiny" model program in C; without a lot of munging around in order to get the data reference offsets; in the code correct.;; If the _TEXT:DGROUP fixup appears in other files (which it does), the linker; will not compute the correct value unless the accumulated data pointer is; zero when it gets there. Therefore, no data should be placed in the data segment; until after all instances of _TEXT:DGROUP have been encountered by the linker.; The linker processes files from right to left on the command line.;;--
.386p
include main.inc
_DATA SEGMENT PARA USE16 PUBLIC 'DATA'
;; Define double wrod to save caller's (ntldr's) stack pointer;
NtldrStack df 0 ; saved area for ss:esp
dw 2048 dup (0)DetectionStack equ $
_DATA ends
_TEXT segment para use16 public 'CODE' ASSUME CS: _TEXT, DS: DGROUP, SS: DGROUP
;++;; VOID; DetectionMain (; ULONG HeapStart,; ULONG HeapSize,; ULONG ConfigurationTree,; ULONG HeapUsed,; ULONG LoadOptions,; ULONG LoadOptionsLength; );; Routine Description:;; This is the entry point of the detection module.; Memory from HeapStart to (HeapStart + HeapSize) is allocated for detection; module to store the hardware configuration tree.; Note that detection module loaded address will be resued by loader after; the control is passed back to ntldr.;; Arguments:;; HeapStart - supplies a 32 bit FLAT starting addr of the heap;; HeapSize - Supplies the size of the useable heap;; ConfigurationTree - Supplies a 32 bit FLAT address of the variable to; receive the configuration tree.;; HeapUsed - Supplies a 32 bit FLAT address of the variable to receive; the size of heap we acually used.;; LoadOptions - Supplies a 32 bit FLAT address of the load options string.;; LoadOptionsLength - Supplies the length of the LoadOptions string. Note,; this is for sanity check to make sure the LoadOptions string is valid.; (in case use usews Nt 1.0 ntldr with the new ntdetect.com.);; Return Value:;; None.;;--;
;; Run-time fixups for stack and data segment;
public DetectionMainDetectionMain:
;; Save all the registers we need to preserved on NTLDR's stack;
push ebp mov ebp, esp and ebp, 0ffffh push ds push es push ebx push esi push edi
;; Compute the paragraph needed for DS;
mov cx,offset _TEXT:DGROUP ; first calculate offset to data shr cx,4 ; must be para aligned
mov ax,cs ; get base of code add ax,cx ; add paragraph offset to data
;; Make DS point to the paragraph address of DGROUP;
mov ds,ax ; ds now points to beginning of DGROUP mov es,ax
;; Save old stack pointer and set up our own stack.;
mov ecx, esp mov dword ptr NtldrStack, ecx mov cx, ss mov word ptr NtldrStack + 4, cx
mov ebx, [bp + 8] ; [ebx] = Heap Start mov ecx, [bp + 12] ; [ecx] = Heap Size mov esi, [bp + 16] ; [esi] -> addr of ConfigurationTree mov edi, [bp + 20] ; [edi] -> Addr of HeapUsed variable mov edx, [bp + 24] ; [edx]-> Addr of LoadOptions string mov ebp, [bp + 28] ; [ebp] = length of LoadOptions
mov ss,ax mov esp,offset DGROUP:DetectionStack ; (ss:esp) = top of internal stack
;; Set up parameters and invoke real detection code to collect hardware; information.;
push ebp push edx push edi push esi push ecx push ebx xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx xor esi, esi xor edi, edi call _HardwareDetection
;; The hardware detection is done. We need to switch to ntldr's stack,; restore registers and return back to ntldr.;
lss esp, NtldrStack
pop edi ; retore registers pop esi pop ebx pop es pop ds pop ebp
retf
_TEXT ends
end DetectionMain
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