NT4/private/ntos/boot/detect/i386/main.asm
2020-09-30 17:12:29 +02:00

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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 DetectionMain
DetectionMain:
;
; 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
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