132 lines
6.3 KiB
Plaintext
132 lines
6.3 KiB
Plaintext
;; Copyright (C) 2019 Jeremiah Orians
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;; This file is part of mescc-tools.
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;;
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;; mescc-tools 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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;; mescc-tools 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 mescc-tools. If not, see <http://www.gnu.org/licenses/>.
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;; Register usage:
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;; EBP => OUTPUT
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;; EDI => Buffer
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;; ESI => INPUT
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## ELF Header
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# :ELF_base
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7F 45 4C 46 # e_ident[EI_MAG0-3] ELF's magic number
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01 # e_ident[EI_CLASS] Indicating 32 bit
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01 # e_ident[EI_DATA] Indicating little endianness
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01 # e_ident[EI_VERSION] Indicating original elf
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00 # e_ident[EI_OSABI] Set at 0 because none cares
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00 # e_ident[EI_ABIVERSION] See above
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00 00 00 00 00 00 00 # e_ident[EI_PAD]
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02 00 # e_type Indicating Executable
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03 00 # e_machine Indicating x86
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01 00 00 00 # e_version Indicating original elf
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54 80 04 08 # e_entry Address of the entry point
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34 00 00 00 # e_phoff Address of program header table
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00 00 00 00 # e_shoff Address of section header table
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00 00 00 00 # e_flags
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34 00 # e_ehsize Indicating our 52 Byte header
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20 00 # e_phentsize size of a program header table
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01 00 # e_phnum number of entries in program table
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00 00 # e_shentsize size of a section header table
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00 00 # e_shnum number of entries in section table
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00 00 # e_shstrndx index of the section names
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## Program Header
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# :ELF_program_headers
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# :ELF_program_header__text
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01 00 00 00 # ph_type: PT-LOAD = 1
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00 00 00 00 # ph_offset
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00 80 04 08 # ph_vaddr
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00 80 04 08 # ph_physaddr
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D7 00 00 00 # ph_filesz
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D7 00 00 00 # ph_memsz
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07 00 00 00 # ph_flags: PF-X|PF-W|PF-R = 7
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01 00 00 00 # ph_align
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# :ELF_text
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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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58 ; POP_EAX ;·Get·the·number·of·arguments
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5B ; POP_EBX ;·Get·the·program·name
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5B ; POP_EBX ;·Get·the·actual·output name
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B9 41020000 ; LOADI32_ECX %577 ; Prepare file as O_WRONLY|O_CREAT|O_TRUNC
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BA 80010000 ; LOADI32_EDX %384 ; Prepare file as RW for owner only (600 in octal)
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B8 05000000 ; LOADI32_EAX %5 ;·the·syscall·number·for·open()
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CD80 ; INT_80 ; Now open that file
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89C5 ; COPY_EAX_to_EBP ; Preserve the file pointer we were given
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B8 2D000000 ; LOADI32_EAX %45 ; the Syscall # for SYS_BRK
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BB 00000000 ; LOADI32_EBX %0 ; Get current brk
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CD80 ; INT_80 ; Let the kernel do the work
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89C7 ; COPY_EAX_to_EDI ; Set our malloc pointer
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B8 2D000000 ; LOADI32_EAX %45 ; the Syscall # for SYS_BRK
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89FB ; COPY_EDI_to_EBX ; Using current pointer
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81C3 00001000 ; ADDI32_EBX %0x100000 ; Allocate 1MB
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CD80 ; INT_80 ; Let the kernel do the work
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# :core
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5B ; POP_EBX ;·Get·the·actual·input name
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81FB 00000000 ; CMPI32_EBX %0 ; Check for null string
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74 3B ; JE8 !done ; Hit null be done
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B9 00000000 ; LOADI32_ECX %0 ;·prepare·read_only
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BA 00000000 ; LOADI32_EDX %0 ; prevent any interactions
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B8 05000000 ; LOADI32_EAX %5 ;·the·syscall·number·for·open()
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CD80 ; INT_80 ; Now open that damn file
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89C6 ; COPY_EAX_to_ESI ; Protect INPUT
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# :keep
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BA 00001000 ; LOADI32_EDX %0x100000 ; set the size of chars we want
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89F9 ; COPY_EDI_to_ECX ; Where to put it
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89F3 ; COPY_ESI_to_EBX ; Where are we reading from
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B8 03000000 ; LOADI32_EAX %3 ; the syscall number for read
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CD80 ; INT_80 ; call the Kernel
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50 ; PUSH_EAX ; Protect the number of bytes read
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89C2 ; COPY_EAX_to_EDX ; Number of bytes to write
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89F9 ; COPY_EDI_to_ECX ; What we are writing
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89EB ; COPY_EBP_to_EBX ; Write to target file
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B8 04000000 ; LOADI32_EAX %4 ; the syscall number for write
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CD80 ; INT_80 ; call the Kernel
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58 ; POP_EAX ; Get bytes read
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3D 00001000 ; CMPI32_EAX %0x100000 ; Check if buffer was fully used
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74 DA ; JE8 !keep ; Keep looping if was full
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EB BC ; JMP8 !core ; Otherwise move to next file
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# :done
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; program completed Successfully
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BB 00000000 ; LOADI32_EBX %0 ; All is well
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B8 01000000 ; LOADI32_EAX %1 ; put the exit syscall number in eax
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CD80 ; INT_80 ; Call it a good day
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# :ELF_end
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