92 lines
1.6 KiB
ArmAsm
92 lines
1.6 KiB
ArmAsm
.code16
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#ifndef REGPARM
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# error "This file assumes -mregparm=3 -DREGPARM=3"
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#endif
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.section ".text","ax"
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.globl _start
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.type _start,@function
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_start:
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# Align the stack and make sure the high half is zero
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andl $0xfffc,%esp
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# DS, ES points to the PSP at this point
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pushw %es # Save PSP pointer
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movw %cs,%ax
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movw %ax,%ds
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movw %ax,%es
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# Clear the .bss
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cld
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xorl %eax,%eax
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movw $__bss_start,%di
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movw $__bss_end+3,%cx
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subw %di,%cx
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shrw $2,%cx
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rep ; stosl
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# Copy the PSP into our own segment
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popw %fs # FS -> PSP
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movw $_PSP,%di
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xorw %si,%si
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movw $0x40,%cx
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fs ; rep ; movsl
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# Verify that this is a supportable DOS version
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movw $0x3001,%ax
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int $0x21
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xchgb %ah,%al
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movw %ax,dos_version
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cmpw $0x0314,%ax # DOS >= 3.20?
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jae 1f # If so, okay
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movw $bad_dos,%dx # Print error message
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movb $0x09,%ah
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int $0x21
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int $0x20 # Die
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1:
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# Compute argc and argv (assumes REGPARM)
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pushl %eax # Make space for argv
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movl %esp,%eax
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calll __parse_argv
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pushl %eax # argc
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# Initialize malloc
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calll __init_memory_arena
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# Now call main
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popl %eax # argc
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popl %edx # argv
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calll main
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# Here %eax is the exit code, fall through into exit
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.size _start,.-_start
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.globl exit
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.type exit,@function
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exit:
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# Exit code already in %eax
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movb $0x4c,%ah # Terminate program
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int $0x21
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1: hlt
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jmp 1b
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.size exit,.-exit
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.section ".rodata","a"
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bad_dos:
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.ascii "Unsupported DOS version\r\n$"
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.size bad_dos,.-bad_dos
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.section ".bss","aw"
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.balign 16
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.globl _PSP
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_PSP:
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.space 256
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.size _PSP, .-_PSP
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/* Purely for sanity */
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.section ".null","a"
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.long 0,0,0,0
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