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/* $Id$ */
/** @file
* BS3Kit - Documentation.
*/
/*
* Copyright (C) 2007-2022 Oracle Corporation
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* you can redistribute it and/or modify it under the terms of the GNU
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*
* The contents of this file may alternatively be used under the terms
* of the Common Development and Distribution License Version 1.0
* (CDDL) only, as it comes in the "COPYING.CDDL" file of the
* VirtualBox OSE distribution, in which case the provisions of the
* CDDL are applicable instead of those of the GPL.
*
* You may elect to license modified versions of this file under the
* terms and conditions of either the GPL or the CDDL or both.
*/
/** @page pg_bs3kit BS3Kit - Boot Sector Kit \#3
*
* The BS3Kit is a framework for bare metal floppy/usb image tests.
*
* The 3rd iteration of the framework includes support for 16-bit and 32-bit
* C/C++ code, with provisions for 64-bit C code to possibly be added later.
* The C code have to do without a runtime library, otherwhat what we can share
* possibly with IPRT.
*
* This iteration also adds a real linker into the picture, which is an
* improvment over early when all had to done in a single assembler run with
* lots of includes and macros controlling what we needed. The functions are no
* in separate files and compiled/assembled into libraries, so the linker will
* only include exactly what is needed. The current linker is the OpenWatcom
* one, wlink, that we're already using when building the BIOSes. If it wasn't
* for the segment/selector fixups in 16-bit code (mostly), maybe we could
* convince the ELF linker from GNU binutils to do the job too (with help from
* the ).
*
*
* @sa grp_bs3kit, grp_bs3kit_tmpl, grp_bs3kit_cmn, grp_bs3kit_mode,
* grp_bs3kit_system
*
* @section sec_calling_convention Calling convention
*
* Because we're not mixing with C code, we will use __cdecl for 16-bit and
* 32-bit code, where as 64-bit code will use the microsoft calling AMD64
* convention. To avoid unnecessary %ifdef'ing in assembly code, we will use a
* macro to load the RCX, RDX, R8 and R9 registers off the stack in 64-bit
* assembly code.
*
* Register treatment in 16-bit __cdecl, 32-bit __cdecl and 64-bit msabi:
*
* | Register | 16-bit | 32-bit | 64-bit | ASM template |
* | ------------ | ----------- | ---------- | --------------- | ------------ |
* | EAX, RAX | volatile | volatile | volatile | volatile |
* | EBX, RBX | volatile | preserved | preserved | both |
* | ECX, RCX | volatile | volatile | volatile, arg 0 | volatile |
* | EDX, RDX | volatile | volatile | volatile, arg 1 | volatile |
* | ESP, RSP | preserved | preserved | preserved | preserved |
* | EBP, RBP | preserved | preserved | preserved | preserved |
* | EDI, RDI | preserved | preserved | preserved | preserved |
* | ESI, RSI | preserved | preserved | preserved | preserved |
* | R8 | volatile | volatile | volatile, arg 2 | volatile |
* | R9 | volatile | volatile | volatile, arg 3 | volatile |
* | R10 | volatile | volatile | volatile | volatile |
* | R11 | volatile | volatile | volatile | volatile |
* | R12 | volatile | volatile | preserved | preserved(*) |
* | R13 | volatile | volatile | preserved | preserved(*) |
* | R14 | volatile | volatile | preserved | preserved(*) |
* | R15 | volatile | volatile | preserved | preserved(*) |
* | RFLAGS.DF | =0 | =0 | =0 | =0 |
* | CS | preserved | preserved | preserved | preserved |
* | DS | preserved! | preserved? | preserved | both |
* | ES | volatile | volatile | preserved | volatile |
* | FS | preserved | preserved | preserved | preserved |
* | GS | preserved | volatile | preserved | both |
* | SS | preserved | preserved | preserved | preserved |
*
* The 'both' here means that we preserve it wrt to our caller, while at the
* same time assuming anything we call will clobber it.
*
* The 'preserved(*)' marking of R12-R15 indicates that they'll be preserved in
* 64-bit mode, but may be changed in certain cases when running 32-bit or
* 16-bit code. This is especially true if switching CPU mode, e.g. from 32-bit
* protected mode to 32-bit long mode.
*
* Return values are returned in the xAX register, but with the following
* caveats for values larger than ARCH_BITS:
* - 16-bit code:
* - 32-bit values are returned in AX:DX, where AX holds bits 15:0 and
* DX bits 31:16.
* - 64-bit values are returned in DX:CX:BX:AX, where DX holds bits
* 15:0, CX bits 31:16, BX bits 47:32, and AX bits 63:48.
* - 32-bit code:
* - 64-bit values are returned in EAX:EDX, where eax holds the least
* significant bits.
*
* The DS segment register is pegged to BS3DATA16_GROUP in 16-bit code so that
* we don't need to reload it all the time. This allows us to modify it in
* ring-0 and mode switching code without ending up in any serious RPL or DPL
* trouble. In 32-bit and 64-bit mode the DS register is a flat, unlimited,
* writable selector.
*
* In 16-bit and 32-bit code we do not assume anything about ES, FS, and GS.
*
*
* For an in depth coverage of x86 and AMD64 calling convensions, see
* http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/function-calling-conventions.html
*
*
*
* @section sec_modes Execution Modes
*
* BS3Kit defines a number of execution modes in order to be able to test the
* full CPU capabilities (that VirtualBox care about anyways). It currently
* omits system management mode, hardware virtualization modes, and security
* modes as those aren't supported by VirtualBox or are difficult to handle.
*
* The modes are categorized into normal and weird ones.
*
* The normal ones are:
* + RM - Real mode.
* + PE16 - Protected mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PE32 - Protected mode running 32-bit code, 32-bit TSS and 32-bit handlers.
* + PEV86 - Protected mode running v8086 code, 32-bit TSS and 32-bit handlers.
* + PP16 - 386 paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PP32 - 386 paged mode running 32-bit code, 32-bit TSS and 32-bit handlers.
* + PPV86 - 386 paged mode running v8086 code, 32-bit TSS and 32-bit handlers.
* + PAE16 - PAE paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PAE32 - PAE paged mode running 32-bit code, 32-bit TSS and 32-bit handlers.
* + PAEV86 - PAE paged mode running v8086 code, 32-bit TSS and 32-bit handlers.
* + LM16 - AMD64 long mode running 16-bit code, 64-bit TSS and 64-bit handlers.
* + LM32 - AMD64 long mode running 32-bit code, 64-bit TSS and 64-bit handlers.
* + LM64 - AMD64 long mode running 64-bit code, 64-bit TSS and 64-bit handlers.
*
* The weird ones:
* + PE16_32 - Protected mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PE16_V86 - Protected mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PE32_16 - Protected mode running 32-bit code, 32-bit TSS and 32-bit handlers.
* + PP16_32 - 386 paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PP16_V86 - 386 paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PP32_16 - 386 paged mode running 32-bit code, 32-bit TSS and 32-bit handlers.
* + PAE16_32 - PAE paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PAE16_V86 - PAE paged mode running 16-bit code, 16-bit TSS and 16-bit handlers.
* + PAE32_16 - PAE paged mode running 32-bit code, 32-bit TSS and 32-bit handlers.
*
* Actually, the PE32_16, PP32_16 and PAE32_16 modes aren't all that weird and fits in
* right next to LM16 and LM32, but this is the way it ended up. :-)
*
*/
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