source: vbox/trunk/src/VBox/Devices/PC/BIOS/pcibio32.asm

; $Id: pcibio32.asm 98103 2023-01-17 14:15:46Z vboxsync $
;; @file
; BIOS32 service directory and 32-bit PCI BIOS entry point
;

;
; Copyright (C) 2006-2023 Oracle and/or its affiliates.
;
; This file is part of VirtualBox base platform packages, as
; available from https://www.virtualbox.org.
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation, in version 3 of the
; License.
;
; This program is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, see <https://www.gnu.org/licenses>.
;
; SPDX-License-Identifier: GPL-3.0-only
; --------------------------------------------------------------------


; Public symbols for debugging only
public          pcibios32_entry
public          bios32_service

; The BIOS32 service directory header must be located in the E0000h-FFFF0h
; range on a paragraph boundary. Note that the actual 32-bit code need not
; be located below 1MB at all.

_DATA           segment public 'DATA'

align   16
bios32_directory:
                db      '_32_'          ; ASCII signature
                dw      bios32_service  ; Entry point address...
                dw      000Fh           ; ...hardcoded to F000 segment
                db      0               ; Revision
                db      1               ; Length in paras - must be 1
                db      0               ; Checksum calculated later
                db      5 dup(0)        ; Unused, must be zero

_DATA           ends

.386

extrn   _pci32_function:near

BIOS32          segment public 'CODE' use32

;
; The BIOS32 Service Directory - must be less than 4K in size (easy!).
;
bios32_service  proc    far

                pushfd

                cmp     bl, 0                   ; Only function 0 supported
                jnz     b32_bad_func

                cmp     eax, 'ICP$'             ; "$PCI"
                mov     al, 80h                 ; Unknown service
                jnz     b32_done

                mov     ebx, 000f0000h          ; Base address (linear)
                mov     ecx, 0f000h             ; Length of service
                mov     edx, pcibios32_entry    ; Entry point offset from base
                xor     al, al                  ; Indicate success
b32_done:
                popfd
                retf

b32_bad_func:
                mov     al, 81h                 ; Unsupported function
                jmp     b32_done

bios32_service  endp

;
; The 32-bit PCI BIOS entry point - simply calls into C code.
;
pcibios32_entry proc    far

                pushfd                          ; Preserve flags
                cld                             ; Just in case...

                push    es                      ; Call into C implementation
                pushad
                call    _pci32_function
                popad
                pop     es

                popfd                           ; Restore flags and return
                retf

pcibios32_entry endp


BIOS32          ends

                end