1 files changed, 151 insertions, 0 deletions
diff --git a/src/VBox/Devices/BiosCommonCode/__U4D.asm b/src/VBox/Devices/BiosCommonCode/__U4D.asm
new file mode 100644
index 00000000..7fb3d58f
--- /dev/null
+++ b/src/VBox/Devices/BiosCommonCode/__U4D.asm
@@ -0,0 +1,151 @@
+; $Id: __U4D.asm $
+;; @file
+; Compiler support routines.
+;
+
+;
+; Copyright (C) 2012-2022 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
+;
+
+
+;*******************************************************************************
+;*  Exported Symbols                                                           *
+;*******************************************************************************
+public          __U4D
+
+; MASM (ML.EXE) is used for PXE and no longer understands the .8086 directive.
+; WASM is used for the BIOS and understands it just fine.
+ifdef __WASM__
+                .8086
+endif
+
+
+if VBOX_BIOS_CPU lt 80386
+extrn _DoUInt32Div:near
+endif
+
+
+_TEXT           segment public 'CODE' use16
+                assume cs:_TEXT
+
+
+;;
+; 32-bit unsigned division.
+;
+; @param    dx:ax   Dividend.
+; @param    cx:bx   Divisor.
+; @returns  dx:ax   Quotient.
+;           cx:bx   Remainder.
+;
+__U4D:
+                pushf
+if VBOX_BIOS_CPU ge 80386
+                .386
+                push    eax
+                push    edx
+                push    ecx
+
+                rol     eax, 16
+                mov     ax, dx
+                ror     eax, 16
+                xor     edx, edx
+
+                shr     ecx, 16
+                mov     cx, bx
+
+                div     ecx                 ; eax:edx / ecx -> eax=quotient, edx=remainder.
+
+                mov     bx, dx
+                pop     ecx
+                shr     edx, 16
+                mov     cx, dx
+
+                pop     edx
+                ror     eax, 16
+                mov     dx, ax
+                add     sp, 2
+                pop     ax
+                rol     eax, 16
+ifdef __WASM__
+                .8086
+endif
+else
+                ;
+                ; If the divisor is only 16-bit, use a fast path
+                ;
+                test    cx, cx
+                jnz     do_it_the_hard_way
+
+                div     bx              ; dx:ax / bx -> ax=quotient, dx=remainder
+
+                mov     bx, dx          ; remainder in cx:bx, and we know cx=0
+
+                xor     dx, dx          ; quotient in dx:ax, dx must be zero
+
+                popf
+                ret
+
+do_it_the_hard_way:
+                ; Call C function do this.
+                push    ds
+                push    es
+
+                ;
+                ; Convert to a C __cdecl call - not doing this in assembly.
+                ;
+
+                ; Set up a frame of sorts, allocating 4 bytes for the result buffer.
+                push    bp
+                sub     sp, 04h
+                mov     bp, sp
+
+                ; Pointer to the return buffer.
+                push    ss
+                push    bp
+                add     bp, 04h                 ; Correct bp.
+
+                ; The divisor.
+                push    cx
+                push    bx
+
+                ; The dividend.
+                push    dx
+                push    ax
+
+                call    _DoUInt32Div
+
+                ; Load the remainder.
+                mov     cx, [bp - 02h]
+                mov     bx, [bp - 04h]
+
+                ; The quotient is already in dx:ax
+
+                mov     sp, bp
+                pop     bp
+                pop     es
+                pop     ds
+endif
+                popf
+                ret
+
+_TEXT           ends
+                end
+