232 lines
8.6 KiB
Plaintext
232 lines
8.6 KiB
Plaintext
## Copyright (C) 2019 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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## 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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65 01 00 00 # ph_filesz
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65 01 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 ; (0x8048054)
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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·input name
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B9 00000000 # LOADI32_ECX %0 ;·prepare·read_only
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BA 00000000 # LOADI32_EDX %0 ; Extra sure
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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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A3 55810408 # STORE32_Absolute32_eax &fin ; Preserve the file pointer we were given
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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 C0010000 # LOADI32_EDX %448 ; Prepare file as RWX for owner only (700 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 damn file
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A3 59810408 # STORE32_Absolute32_eax &fout ; Preserve the file pointer we were given
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; Our flag for byte processing
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BD FFFFFFFF # LOADI32_EBP %-1
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; temp storage for the sum
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BF 00000000
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#:loop ; (0x804808E)
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; Read a byte
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E8 9E000000 # CALL %Read_byte
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; process byte
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E8 29000000 # CALL %hex
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; Deal with -1 values
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83F8 00 # CMPI8_EAX !0
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7C F1 # JL8 !loop
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; deal with toggle
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83FD 00 # CMPI8_EBP !0
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7D 09 # JGE8 !print
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; process first byte of pair
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89C7 # COPY_EAX_to_EDI
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BD 00000000 # LOADI32_EBP %0
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EB E3 # JMP8 !loop
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; process second byte of pair
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#:print ; (0x80480AB)
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; update the sum and store in output
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C1E7 04 # SHLI8_EDI !4
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01F8 # ADD_EDI_to_EAX
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A2 5D810408 # STORE8_Absolute32_al &output
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; flip the toggle
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BD FFFFFFFF # LOADI32_EBP %-1
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E8 5A000000 # CALL %write_byte
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EB CD # JMP8 !loop
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#:hex ; (0x80480C1)
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; Purge Comment Lines (#)
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83F8 23 # CMPI8_EAX !35
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74 25 # JE8 !purge_comment
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; Purge Comment Lines (;)
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83F8 3B # CMPI8_EAX !59
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74 20 # JE8 !purge_comment
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; deal all ascii less than 0
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83F8 30 # CMPI8_EAX !48
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7C 37 # JL8 !ascii_other
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; deal with 0-9
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83F8 3A # CMPI8_EAX !58
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7C 26 # JL8 !ascii_num
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; deal with all ascii less than A
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83F8 41 # CMPI8_EAX !65
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7C 2D # JL8 !ascii_other
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; deal with A-F
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83F8 47 # CMPI8_EAX !71
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7C 24 # JL8 !ascii_high
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;deal with all ascii less than a
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83F8 61 # CMPI8_EAX !97
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7C 23 # JL8 !ascii_other
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;deal with a-f
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83F8 67 # CMPI8_EAX !103
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7C 16 # JL8 !ascii_low
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; The rest that remains needs to be ignored
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EB 1C # JMP8 !ascii_other
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#:purge_comment ; (0x80480EB)
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; Read a byte
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E8 41000000 # CALL %Read_byte
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; Loop if not LF
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83F8 0A # CMPI8_EAX !10
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75 F6 # JNE8 !purge_comment
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; Otherwise return -1
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B8 FFFFFFFF # LOADI32_EAX %-1
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C3 # RET
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#:ascii_num ; (0x80480FB)
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83E8 30 # SUBI8_EAX !48
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C3 # RET
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#:ascii_low ; (0x80480FF)
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83E8 57 # SUBI8_EAX !87
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C3 # RET
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#:ascii_high ; (0x8048103)
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83E8 37 # SUBI8_EAX !55
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C3 # RET
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#:ascii_other ; (0x8048107)
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B8 FFFFFFFF # LOADI32_EAX %-1
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C3 # RET
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#:Done ; (0x804810D)
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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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#:write_byte ; (0x8048119)
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; Print our Hex
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BA 01000000 # LOADI32_EDX %1 ; set the size of chars we want
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B9 5D810408 # LOADI32_ECX &output ; What we are writing
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8B1D 59810408 # LOAD32_Absolute32_ebx &fout ; Where are we writing to
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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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C3 # RET
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#:Read_byte ; (0x8048131)
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; Attempt to read 1 byte from STDIN
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BA 01000000 # LOADI32_EDX %1 ; set the size of chars we want
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B9 61810408 # LOADI32_ECX &input ; Where to put it
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8B1D 55810408 # LOAD32_Absolute32_ebx &fin ; 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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85C0 # TEST ; check what we got
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74 C1 # JE8 !Done ; Got EOF call it done
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; load byte
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A0 61810408 # LOAD8_Absolute32_al &input ; load char
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0FB6C0 # MOVZX ; We have to zero extend it to use it
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C3 # RET
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#:fin ; (0x8048155)
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00000000 # NULL
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#:fout ; (0x8048159)
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00000000 # NULL
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#:output ; (0x804815D)
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00000000 # NULL
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#:input ; (0x8048161)
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00000000 # NULL
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#:ELF_end
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