397 lines
10 KiB
ArmAsm
397 lines
10 KiB
ArmAsm
/*
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* Copyright (c) 1998 Robert Nordier
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are freely
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* permitted provided that the above copyright notice and this
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* paragraph and the following disclaimer are duplicated in all
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* such forms.
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*
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* This software is provided "AS IS" and without any express or
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* implied warranties, including, without limitation, the implied
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* warranties of merchantability and fitness for a particular
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* purpose.
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*
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* $FreeBSD$
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*/
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/*
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* Prototype BTX loader program, written in a couple of hours. The
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* real thing should probably be more flexible, and in C.
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*/
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/*
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* Memory locations.
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*/
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.set MEM_STUB,0x600 # Real mode stub
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.set MEM_ESP,0x1000 # New stack pointer
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.set MEM_TBL,0x5000 # BTX page tables
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.set MEM_ENTRY,0x9010 # BTX entry point
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.set MEM_DATA,start+0x1000 # Data segment
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/*
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* Segment selectors.
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*/
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.set SEL_SCODE,0x8 # 4GB code
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.set SEL_SDATA,0x10 # 4GB data
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.set SEL_RCODE,0x18 # 64K code
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.set SEL_RDATA,0x20 # 64K data
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/*
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* Paging constants.
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*/
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.set PAG_SIZ,0x1000 # Page size
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.set PAG_ENT,0x4 # Page entry size
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/*
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* Screen constants.
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*/
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.set SCR_MAT,0x7 # Mode/attribute
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.set SCR_COL,0x50 # Columns per row
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.set SCR_ROW,0x19 # Rows per screen
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/*
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* BIOS Data Area locations.
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*/
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.set BDA_MEM,0x413 # Free memory
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.set BDA_SCR,0x449 # Video mode
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.set BDA_POS,0x450 # Cursor position
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/*
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* Required by aout gas inadequacy.
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*/
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.set SIZ_STUB,0x1a # Size of stub
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/*
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* We expect to be loaded by boot2 at the origin defined in ./Makefile.
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*/
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.globl start
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/*
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* BTX program loader for ELF clients.
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*/
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start: cld # String ops inc
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movl $m_logo,%esi # Identify
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call putstr # ourselves
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movzwl BDA_MEM,%eax # Get base memory
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shll $0xa,%eax # in bytes
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movl %eax,%ebp # Base of user stack
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#ifdef BTXLDR_VERBOSE
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movl $m_mem,%esi # Display
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call hexout # amount of
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call putstr # base memory
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#endif
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lgdt gdtdesc # Load new GDT
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/*
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* Relocate caller's arguments.
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*/
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#ifdef BTXLDR_VERBOSE
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movl $m_esp,%esi # Display
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movl %esp,%eax # caller
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call hexout # stack
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call putstr # pointer
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movl $m_args,%esi # Format string
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leal 0x4(%esp,1),%ebx # First argument
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movl $0x6,%ecx # Count
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start.1: movl (%ebx),%eax # Get argument and
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addl $0x4,%ebx # bump pointer
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call hexout # Display it
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loop start.1 # Till done
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call putstr # End message
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#endif
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movl $0x48,%ecx # Allocate space
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subl %ecx,%ebp # for bootinfo
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movl 0x18(%esp,1),%esi # Source: bootinfo
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cmpl $0x0, %esi # If the bootinfo pointer
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je start_null_bi # is null, don't copy it
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movl %ebp,%edi # Destination
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rep # Copy
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movsb # it
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movl %ebp,0x18(%esp,1) # Update pointer
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#ifdef BTXLDR_VERBOSE
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movl $m_rel_bi,%esi # Display
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movl %ebp,%eax # bootinfo
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call hexout # relocation
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call putstr # message
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#endif
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start_null_bi: movl $0x18,%ecx # Allocate space
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subl %ecx,%ebp # for arguments
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leal 0x4(%esp,1),%esi # Source
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movl %ebp,%edi # Destination
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rep # Copy
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movsb # them
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#ifdef BTXLDR_VERBOSE
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movl $m_rel_args,%esi # Display
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movl %ebp,%eax # argument
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call hexout # relocation
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call putstr # message
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#endif
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/*
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* Set up BTX kernel.
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*/
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movl $MEM_ESP,%esp # Set up new stack
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movl $MEM_DATA,%ebx # Data segment
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movl $m_vers,%esi # Display BTX
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call putstr # version message
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movb 0x5(%ebx),%al # Get major version
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addb $'0',%al # Display
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call putchr # it
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movb $'.',%al # And a
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call putchr # dot
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movb 0x6(%ebx),%al # Get minor
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xorb %ah,%ah # version
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movb $0xa,%dl # Divide
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divb %dl,%al # by 10
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addb $'0',%al # Display
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call putchr # tens
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movb %ah,%al # Get units
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addb $'0',%al # Display
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call putchr # units
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call putstr # End message
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movl %ebx,%esi # BTX image
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movzwl 0x8(%ebx),%edi # Compute
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orl $PAG_SIZ/PAG_ENT-1,%edi # the
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incl %edi # BTX
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shll $0x2,%edi # load
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addl $MEM_TBL,%edi # address
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pushl %edi # Save load address
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movzwl 0xa(%ebx),%ecx # Image size
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#ifdef BTXLDR_VERBOSE
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pushl %ecx # Save image size
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#endif
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rep # Relocate
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movsb # BTX
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movl %esi,%ebx # Keep place
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#ifdef BTXLDR_VERBOSE
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movl $m_rel_btx,%esi # Restore
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popl %eax # parameters
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call hexout # and
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#endif
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popl %ebp # display
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#ifdef BTXLDR_VERBOSE
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movl %ebp,%eax # the
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call hexout # relocation
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call putstr # message
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#endif
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addl $PAG_SIZ,%ebp # Display
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#ifdef BTXLDR_VERBOSE
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movl $m_base,%esi # the
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movl %ebp,%eax # user
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call hexout # base
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call putstr # address
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#endif
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/*
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* Set up ELF-format client program.
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*/
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cmpl $0x464c457f,(%ebx) # ELF magic number?
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je start.3 # Yes
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movl $e_fmt,%esi # Display error
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call putstr # message
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start.2: jmp start.2 # Hang
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start.3:
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#ifdef BTXLDR_VERBOSE
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movl $m_elf,%esi # Display ELF
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call putstr # message
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movl $m_segs,%esi # Format string
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#endif
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movl $0x2,%edi # Segment count
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movl 0x1c(%ebx),%edx # Get e_phoff
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addl %ebx,%edx # To pointer
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movzwl 0x2c(%ebx),%ecx # Get e_phnum
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start.4: cmpl $0x1,(%edx) # Is p_type PT_LOAD?
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jne start.6 # No
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#ifdef BTXLDR_VERBOSE
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movl 0x4(%edx),%eax # Display
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call hexout # p_offset
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movl 0x8(%edx),%eax # Display
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call hexout # p_vaddr
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movl 0x10(%edx),%eax # Display
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call hexout # p_filesz
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movl 0x14(%edx),%eax # Display
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call hexout # p_memsz
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call putstr # End message
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#endif
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pushl %esi # Save
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pushl %edi # working
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pushl %ecx # registers
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movl 0x4(%edx),%esi # Get p_offset
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addl %ebx,%esi # as pointer
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movl 0x8(%edx),%edi # Get p_vaddr
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addl %ebp,%edi # as pointer
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movl 0x10(%edx),%ecx # Get p_filesz
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rep # Set up
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movsb # segment
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movl 0x14(%edx),%ecx # Any bytes
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subl 0x10(%edx),%ecx # to zero?
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jz start.5 # No
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xorb %al,%al # Then
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rep # zero
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stosb # them
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start.5: popl %ecx # Restore
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popl %edi # working
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popl %esi # registers
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decl %edi # Segments to do
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je start.7 # If none
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start.6: addl $0x20,%edx # To next entry
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loop start.4 # Till done
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start.7:
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#ifdef BTXLDR_VERBOSE
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movl $m_done,%esi # Display done
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call putstr # message
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#endif
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movl $start.8,%esi # Real mode stub
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movl $MEM_STUB,%edi # Destination
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movl $start.9-start.8,%ecx # Size
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rep # Relocate
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movsb # it
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ljmp $SEL_RCODE,$MEM_STUB # To 16-bit code
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.code16
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start.8: xorw %ax,%ax # Data
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movb $SEL_RDATA,%al # selector
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movw %ax,%ss # Reload SS
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movw %ax,%ds # Reset
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movw %ax,%es # other
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movw %ax,%fs # segment
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movw %ax,%gs # limits
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movl %cr0,%eax # Switch to
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decw %ax # real
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movl %eax,%cr0 # mode
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ljmp $0,$MEM_ENTRY # Jump to BTX entry point
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start.9:
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.code32
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/*
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* Output message [ESI] followed by EAX in hex.
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*/
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hexout: pushl %eax # Save
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call putstr # Display message
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popl %eax # Restore
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pushl %esi # Save
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pushl %edi # caller's
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movl $buf,%edi # Buffer
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pushl %edi # Save
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call hex32 # To hex
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xorb %al,%al # Terminate
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stosb # string
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popl %esi # Restore
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hexout.1: lodsb # Get a char
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cmpb $'0',%al # Leading zero?
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je hexout.1 # Yes
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testb %al,%al # End of string?
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jne hexout.2 # No
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decl %esi # Undo
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hexout.2: decl %esi # Adjust for inc
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call putstr # Display hex
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popl %edi # Restore
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popl %esi # caller's
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ret # To caller
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/*
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* Output zero-terminated string [ESI] to the console.
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*/
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putstr.0: call putchr # Output char
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putstr: lodsb # Load char
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testb %al,%al # End of string?
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jne putstr.0 # No
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ret # To caller
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/*
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* Output character AL to the console.
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*/
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putchr: pusha # Save
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xorl %ecx,%ecx # Zero for loops
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movb $SCR_MAT,%ah # Mode/attribute
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movl $BDA_POS,%ebx # BDA pointer
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movw (%ebx),%dx # Cursor position
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movl $0xb8000,%edi # Regen buffer (color)
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cmpb %ah,BDA_SCR-BDA_POS(%ebx) # Mono mode?
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jne putchr.1 # No
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xorw %di,%di # Regen buffer (mono)
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putchr.1: cmpb $0xa,%al # New line?
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je putchr.2 # Yes
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xchgl %eax,%ecx # Save char
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movb $SCR_COL,%al # Columns per row
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mulb %dh # * row position
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addb %dl,%al # + column
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adcb $0x0,%ah # position
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shll %eax # * 2
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xchgl %eax,%ecx # Swap char, offset
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movw %ax,(%edi,%ecx,1) # Write attr:char
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incl %edx # Bump cursor
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cmpb $SCR_COL,%dl # Beyond row?
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jb putchr.3 # No
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putchr.2: xorb %dl,%dl # Zero column
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incb %dh # Bump row
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putchr.3: cmpb $SCR_ROW,%dh # Beyond screen?
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jb putchr.4 # No
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leal 2*SCR_COL(%edi),%esi # New top line
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movw $(SCR_ROW-1)*SCR_COL/2,%cx # Words to move
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rep # Scroll
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movsl # screen
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movb $' ',%al # Space
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movb $SCR_COL,%cl # Columns to clear
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rep # Clear
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stosw # line
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movb $SCR_ROW-1,%dh # Bottom line
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putchr.4: movw %dx,(%ebx) # Update position
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popa # Restore
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ret # To caller
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/*
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* Convert EAX, AX, or AL to hex, saving the result to [EDI].
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*/
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hex32: pushl %eax # Save
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shrl $0x10,%eax # Do upper
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call hex16 # 16
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popl %eax # Restore
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hex16: call hex16.1 # Do upper 8
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hex16.1: xchgb %ah,%al # Save/restore
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hex8: pushl %eax # Save
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shrb $0x4,%al # Do upper
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call hex8.1 # 4
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popl %eax # Restore
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hex8.1: andb $0xf,%al # Get lower 4
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cmpb $0xa,%al # Convert
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sbbb $0x69,%al # to hex
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das # digit
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orb $0x20,%al # To lower case
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stosb # Save char
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ret # (Recursive)
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.data
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.p2align 4
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/*
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* Global descriptor table.
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*/
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gdt: .word 0x0,0x0,0x0,0x0 # Null entry
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.word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE
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.word 0xffff,0x0,0x9200,0xcf # SEL_SDATA
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.word 0xffff,0x0,0x9a00,0x0 # SEL_RCODE
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.word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
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gdt.1:
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gdtdesc: .word gdt.1-gdt-1 # Limit
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.long gdt # Base
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/*
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* Messages.
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*/
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m_logo: .asciz " \nBTX loader 1.00 "
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m_vers: .asciz "BTX version is \0\n"
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e_fmt: .asciz "Error: Client format not supported\n"
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#ifdef BTXLDR_VERBOSE
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m_mem: .asciz "Starting in protected mode (base mem=\0)\n"
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m_esp: .asciz "Arguments passed (esp=\0):\n"
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m_args: .asciz"<howto="
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.asciz" bootdev="
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.asciz" junk="
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.asciz" "
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.asciz" "
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.asciz" bootinfo=\0>\n"
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m_rel_bi: .asciz "Relocated bootinfo (size=48) to \0\n"
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m_rel_args: .asciz "Relocated arguments (size=18) to \0\n"
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m_rel_btx: .asciz "Relocated kernel (size=\0) to \0\n"
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m_base: .asciz "Client base address is \0\n"
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m_elf: .asciz "Client format is ELF\n"
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m_segs: .asciz "text segment: offset="
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.asciz " vaddr="
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.asciz " filesz="
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.asciz " memsz=\0\n"
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.asciz "data segment: offset="
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.asciz " vaddr="
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.asciz " filesz="
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.asciz " memsz=\0\n"
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m_done: .asciz "Loading complete\n"
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#endif
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/*
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* Uninitialized data area.
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*/
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buf: # Scratch buffer
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