192 lines
4.1 KiB
ArmAsm
192 lines
4.1 KiB
ArmAsm
;; Copyright (C) 2017 Jeremiah Orians
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;; This file is part of stage0.
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;;
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;; stage0 is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;;
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;; stage0 is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU 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 stage0. If not, see <http://www.gnu.org/licenses/>.
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section .text
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global _start
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; Where the ELF Header is going to hit
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; Simply jump to _start
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; Our main function
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_start:
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pop eax ;·Get·the·number·of·arguments
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pop ebx ;·Get·the·program·name
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pop ebx ;·Get·the·actual·input name
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mov ecx, 0 ;·prepare·read_only
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mov edx, 0 ; Extra sure
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mov eax, 5 ;·the·syscall·number·for·open()
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int 0x80 ; Now open that damn file
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mov [fin], eax ; Preserve the file pointer we were given
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pop ebx ;·Get·the·actual·output name
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mov ecx, 577 ; Prepare file as O_WRONLY|O_CREAT|O_TRUNC
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mov edx, 448 ; Prepare file as RWX for owner only (700 in octal)
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mov eax, 5 ;·the·syscall·number·for·open()
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int 0x80 ; Now open that damn file
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mov [fout], eax ; Preserve the file pointer we were given
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; Our flag for byte processing
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mov ebp, -1
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; temp storage for the sum
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mov edi, 0
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loop:
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; Read a byte
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call Read_byte
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; process byte
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call hex
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; Deal with -1 values
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cmp eax, 0
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jl loop
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; deal with toggle
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cmp ebp, 0
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jge print
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; process first byte of pair
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mov edi, eax
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mov ebp, 0
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jmp loop
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; process second byte of pair
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print:
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; update the sum and store in output
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shl edi, 4
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add eax, edi
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mov [output], al
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; flip the toggle
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mov ebp, -1
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call write_byte
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jmp loop
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hex:
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; Purge Comment Lines (#)
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cmp eax, 35
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je purge_comment
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; Purge Comment Lines (;)
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cmp eax, 59
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je purge_comment
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; deal all ascii less than 0
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cmp eax, 48
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jl ascii_other
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; deal with 0-9
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cmp eax, 58
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jl ascii_num
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; deal with all ascii less than A
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cmp eax, 65
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jl ascii_other
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; deal with A-F
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cmp eax, 71
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jl ascii_high
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;deal with all ascii less than a
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cmp eax, 97
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jl ascii_other
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;deal with a-f
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cmp eax, 103
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jl ascii_low
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; The rest that remains needs to be ignored
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jmp ascii_other
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purge_comment:
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; Read a byte
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call Read_byte
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; Loop if not LF
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cmp eax, 10
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jne purge_comment
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; Otherwise return -1
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mov eax, -1
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ret
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ascii_num:
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sub eax, 48
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ret
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ascii_low:
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sub eax, 87
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ret
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ascii_high:
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sub eax, 55
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ret
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ascii_other:
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mov eax, -1
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ret
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Done:
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; program completed Successfully
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mov ebx, 0 ; All is well
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mov eax, 1 ; put the exit syscall number in eax
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int 0x80 ; Call it a good day
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write_byte:
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; Print our Hex
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mov edx, 1 ; set the size of chars we want
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mov ecx, output ; What we are writing
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mov ebx, [fout] ; Where are we writing to
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mov eax, 4 ; the syscall number for write
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int 0x80 ; call the Kernel
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ret
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Read_byte:
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; Attempt to read 1 byte from STDIN
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mov edx, 1 ; set the size of chars we want
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mov ecx, input ; Where to put it
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mov ebx, [fin] ; Where are we reading from
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mov eax, 3 ; the syscall number for read
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int 0x80 ; call the Kernel
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test eax, eax ; check what we got
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je Done ; Got EOF call it done
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; load byte
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mov al, [input] ; load char
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movzx eax, al ; We have to zero extend it to use it
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ret
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section .data
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ELF_end:
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fin:
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dq 0
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fout:
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dq 0
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; Where we are putting our output
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output:
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; Reserve 4bytes of Zeros
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dq 0
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; Where we get our input
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input:
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; Reserve 4bytes of Zeros
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dq 0
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