mirror of
https://github.com/xcat2/xNBA.git
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429 lines
9.9 KiB
ArmAsm
429 lines
9.9 KiB
ArmAsm
/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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/**
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* High memory temporary load address
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*
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* Temporary buffer into which to copy (or decompress) our runtime
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* image, prior to calling get_memmap() and relocate(). We don't
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* actually leave anything here once install() has returned.
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*
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* We use the start of an even megabyte so that we don't have to worry
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* about the current state of the A20 line.
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*
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* We use 4MB rather than 2MB because there is at least one commercial
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* PXE ROM ("Broadcom UNDI, PXE-2.1 (build 082) v2.0.4") which stores
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* data required by the UNDI ROM loader (yes, the ROM loader; that's
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* the component which should be impossible to damage short of
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* screwing with the MMU) around the 2MB mark. Sadly, this is not a
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* joke.
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*
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*/
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#define HIGHMEM_LOADPOINT ( 4 << 20 )
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#define CR0_PE 1
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.arch i386
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.section ".prefix.lib", "awx", @progbits
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.section ".data16", "aw", @progbits
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/****************************************************************************
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* install_block (real-mode near call)
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*
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* Install block to specified address
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*
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* Parameters:
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* %esi : byte offset within loaded image (must be a multiple of 16)
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* %es:edi : destination address
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* %ecx : length of (decompressed) data
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* %edx : total length of block (including any uninitialised data portion)
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* Returns:
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* none
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* Corrupts:
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* %esi, %edi, %ecx, %edx
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****************************************************************************
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*/
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.section ".prefix.lib"
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.code16
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install_block:
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/* Preserve registers */
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pushw %ds
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pushl %eax
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/* Starting segment => %ds */
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movw %cs, %ax
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shrl $4, %esi
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addw %si, %ax
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movw %ax, %ds
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xorl %esi, %esi
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/* Calculate start and length of uninitialised data portion */
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addr32 leal (%edi,%ecx), %eax
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subl %ecx, %edx
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/* Do the copy */
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cld
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rep addr32 movsb /* or "call decompress16" */
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/* Zero remaining space */
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movl %eax, %edi
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movl %edx, %ecx
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xorb %al, %al
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rep addr32 stosb
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/* Restore registers */
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popl %eax
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popw %ds
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ret
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.size install_block, . - install_block
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/****************************************************************************
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* alloc_basemem (real-mode near call)
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*
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* Allocate space for .text16 and .data16 from top of base memory.
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* Memory is allocated using the BIOS free base memory counter at
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* 0x40:13.
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*
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* Parameters:
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* none
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* Returns:
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* %ax : .text16 segment address
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* %bx : .data16 segment address
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* Corrupts:
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* none
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****************************************************************************
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*/
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.section ".prefix.lib"
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.code16
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alloc_basemem:
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/* FBMS => %ax as segment address */
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movw $0x40, %ax
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movw %ax, %fs
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movw %fs:0x13, %ax
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shlw $6, %ax
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/* .data16 segment address */
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subw $_data16_size_pgh, %ax
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pushw %ax
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/* .text16 segment address */
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subw $_text16_size_pgh, %ax
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pushw %ax
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/* Update FBMS */
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shrw $6, %ax
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movw %ax, %fs:0x13
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/* Return */
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popw %ax
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popw %bx
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ret
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.size alloc_basemem, . - alloc_basemem
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/****************************************************************************
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* install_basemem (real-mode near call)
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*
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* Install .text16 and .data16 into base memory
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*
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* Parameters:
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* %ax : .text16 segment address
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* %bx : .data16 segment address
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* Returns:
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* none
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* Corrupts:
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* none
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****************************************************************************
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*/
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.section ".prefix.lib"
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.code16
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install_basemem:
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/* Preserve registers */
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pushw %es
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pushl %esi
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pushl %edi
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pushl %ecx
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pushl %edx
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/* Install .text16 */
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movw %ax, %es
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xorl %edi, %edi
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movl $_text16_load_offset, %esi
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movl $_text16_size, %ecx
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movl %ecx, %edx
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call install_block
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/* Install .data16 */
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movw %bx, %es
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xorl %edi, %edi
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movl $_data16_load_offset, %esi
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movl $_data16_progbits_size, %ecx
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movl $_data16_size, %edx
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call install_block
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/* Restore registers */
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popl %edx
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popl %ecx
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popl %edi
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popl %esi
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popw %es
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ret
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.size install_basemem, . - install_basemem
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/****************************************************************************
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* install_highmem (flat real-mode near call)
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*
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* Install .text and .data into high memory
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*
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* Parameters:
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* %es:edi : address in high memory
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* Returns:
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* none
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* Corrupts:
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* none
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****************************************************************************
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*/
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#ifndef KEEP_IT_REAL
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.section ".prefix.lib"
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.code16
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install_highmem:
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/* Preserve registers */
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pushl %esi
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pushl %edi
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pushl %ecx
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pushl %edx
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/* Install .text and .data to specified address */
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movl $_textdata_load_offset, %esi
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movl $_textdata_progbits_size, %ecx
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movl $_textdata_size, %edx
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call install_block
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/* Restore registers and interrupt status */
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popl %edx
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popl %ecx
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popl %edi
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popl %esi
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ret
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.size install_highmem, . - install_highmem
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#endif /* KEEP_IT_REAL */
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/****************************************************************************
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* GDT for flat real mode
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*
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* We only ever use this GDT to set segment limits; the bases are
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* unused. Also, we only change data segments, so we don't need to
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* worry about the code or stack segments. This makes everything much
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* simpler.
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****************************************************************************
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*/
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#ifndef KEEP_IT_REAL
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.section ".prefix.lib"
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.align 16
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gdt:
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gdt_limit: .word gdt_length - 1
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gdt_base: .long 0
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.word 0 /* padding */
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flat_ds: /* Flat real mode data segment */
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.equ FLAT_DS, flat_ds - gdt
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.word 0xffff, 0
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.byte 0, 0x93, 0xcf, 0
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real_ds: /* Normal real mode data segment */
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.equ REAL_DS, real_ds - gdt
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.word 0xffff, 0
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.byte 0, 0x93, 0x00, 0
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gdt_end:
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.equ gdt_length, gdt_end - gdt
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.size gdt, . - gdt
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#endif /* KEEP_IT_REAL */
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/****************************************************************************
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* set_real_mode_limits (real-mode near call)
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*
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* Sets limits on the data segments %ds and %es.
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*
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* Parameters:
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* %cx : segment type (FLAT_DS for 4GB or REAL_DS for 64kB)
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****************************************************************************
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*/
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#ifndef KEEP_IT_REAL
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.section ".prefix.lib"
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.code16
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set_real_mode_limits:
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/* Preserve real-mode segment values and temporary registers */
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pushw %es
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pushw %ds
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pushw %bp
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pushl %eax
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/* Set GDT base and load GDT */
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xorl %eax, %eax
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movw %cs, %ax
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shll $4, %eax
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addl $gdt, %eax
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pushl %eax
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pushw %cs:gdt_limit
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movw %sp, %bp
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lgdt (%bp)
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addw $6, %sp
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/* Switch to protected mode */
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movl %cr0, %eax
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orb $CR0_PE, %al
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movl %eax, %cr0
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/* Set flat segment limits */
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movw %cx, %ds
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movw %cx, %es
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/* Switch back to real mode */
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movl %cr0, %eax
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andb $0!CR0_PE, %al
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movl %eax, %cr0
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/* Restore real-mode segment values and temporary registers */
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popl %eax
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popw %bp
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popw %ds
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popw %es
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ret
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.size set_real_mode_limits, . - set_real_mode_limits
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#endif /* KEEP_IT_REAL */
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/****************************************************************************
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* install (real-mode near call)
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* install_prealloc (real-mode near call)
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*
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* Install all text and data segments.
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*
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* Parameters:
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* %ax : .text16 segment address (install_prealloc only)
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* %bx : .data16 segment address (install_prealloc only)
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* Returns:
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* %ax : .text16 segment address
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* %bx : .data16 segment address
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* %edi : .text physical address (if applicable)
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* Corrupts:
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* none
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****************************************************************************
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*/
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.section ".prefix.lib"
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.code16
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.globl install
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install:
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/* Allocate space for .text16 and .data16 */
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call alloc_basemem
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.size install, . - install
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.globl install_prealloc
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install_prealloc:
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/* Install .text16 and .data16 */
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call install_basemem
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#ifdef KEEP_IT_REAL
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/* Preserve %ds, call init_libkir, restore registers */
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pushw %ds
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movw %bx, %ds
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movw %ax, (init_libkir_vector+2)
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lcall *init_libkir_vector
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popw %ds
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#else
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/* Preserve registers and interrupt status, and disable interrupts */
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pushfw
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pushw %ds
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pushw %es
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pushl %esi
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pushl %ecx
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cli
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/* Load up %ds and %es, and set up vectors for far calls to .text16 */
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movw %bx, %ds
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xorw %si, %si
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movw %si, %es
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movw %ax, (init_librm_vector+2)
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movw %ax, (prot_call_vector+2)
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/* Install .text and .data to temporary area in high memory,
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* prior to reading the E820 memory map and relocating
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* properly.
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*/
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movw $FLAT_DS, %cx
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call set_real_mode_limits
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movl $HIGHMEM_LOADPOINT, %edi
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call install_highmem
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/* Set up initial protected-mode GDT, call relocate().
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* relocate() will return with %esi, %edi and %ecx set up
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* ready for the copy to the new location.
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*/
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lcall *init_librm_vector
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pushl $relocate
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lcall *prot_call_vector
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addw $4, %sp
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/* Move code to new location, set up new protected-mode GDT */
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movw $FLAT_DS, %cx
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call set_real_mode_limits
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pushl %edi
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es rep addr32 movsb
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popl %edi
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lcall *init_librm_vector
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/* Restore real-mode segment limits */
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movw $REAL_DS, %cx
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call set_real_mode_limits
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/* Restore registers and interrupt status */
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popl %ecx
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popl %esi
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popw %es
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popw %ds
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popfw
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#endif
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ret
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.size install_prealloc, . - install_prealloc
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/* Vectors for far calls to .text16 functions */
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.section ".data16"
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#ifdef KEEP_IT_REAL
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init_libkir_vector:
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.word init_libkir
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.word 0
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.size init_libkir_vector, . - init_libkir_vector
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#else
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init_librm_vector:
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.word init_librm
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.word 0
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.size init_librm_vector, . - init_librm_vector
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prot_call_vector:
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.word prot_call
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.word 0
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.size prot_call_vector, . - prot_call_vector
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#endif
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