### Copyright (C) 2016 Jeremiah Orians ### This file is part of stage0. ### ### stage0 is free software: you can redistribute it and/or modify ### it under the terms of the GNU General Public License as published by ### the Free Software Foundation, either version 3 of the License, or ### (at your option) any later version. ### ### stage0 is distributed in the hope that it will be useful, ### but WITHOUT ANY WARRANTY; without even the implied warranty of ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ### GNU General Public License for more details. ### ### You should have received a copy of the GNU General Public License ### along with stage0. If not, see . ## ELF Header #:ELF_base 7F 45 4C 46 # e_ident[EI_MAG0-3] ELF's magic number 01 # e_ident[EI_CLASS] Indicating 32 bit 01 # e_ident[EI_DATA] Indicating little endianness 01 # e_ident[EI_VERSION] Indicating original elf 00 # e_ident[EI_OSABI] Set at 0 because none cares 00 # e_ident[EI_ABIVERSION] See above 00 00 00 00 00 00 00 # e_ident[EI_PAD] 02 00 # e_type Indicating Executable 03 00 # e_machine Indicating x86 01 00 00 00 # e_version Indicating original elf 54 80 04 08 # e_entry Address of the entry point 34 00 00 00 # e_phoff Address of program header table 00 00 00 00 # e_shoff Address of section header table 00 00 00 00 # e_flags 34 00 # e_ehsize Indicating our 52 Byte header 20 00 # e_phentsize size of a program header table 01 00 # e_phnum number of entries in program table 00 00 # e_shentsize size of a section header table 00 00 # e_shnum number of entries in section table 00 00 # e_shstrndx index of the section names ## Program Header #:ELF_program_headers #:ELF_program_header__text 01 00 00 00 # ph_type: PT-LOAD = 1 00 00 00 00 # ph_offset 00 80 04 08 # ph_vaddr 00 80 04 08 # ph_physaddr B1 02 00 00 # ph_filesz B1 02 00 00 # ph_memsz 07 00 00 00 # ph_flags: PF-X|PF-W|PF-R = 7 01 00 00 00 # ph_align #:ELF_text #:_start 58 # POP_EAX ;·Get·the·number·of·arguments 5B # POP_EBX ;·Get·the·program·name 5B # POP_EBX ;·Get·the·actual·input name B9 00000000 # LOADI32_ECX %0 ;·prepare·read_only BA 00000000 # LOADI32_EDX %0 ;·extra sure B8 05000000 # LOADI32_EAX %5 ;·the·syscall·number·for·open() CD80 # INT_80 ; Now open that damn file A3 A9820408 # STORE32_Absolute32_eax &fin ; Preserve the file pointer we were given 5B # POP_EBX ;·Get·the·actual·output name B9 41020000 # LOADI32_ECX %577 ; Prepare file as O_WRONLY|O_CREAT|O_TRUNC BA C0010000 # LOADI32_EDX %448 ; Prepare file as RWX for owner only (700 in octal) B8 05000000 # LOADI32_EAX %5 ;·the·syscall·number·for·open() CD80 # INT_80 ; Now open that damn file A3 AD820408 # STORE32_Absolute32_eax &fout ; Preserve the file pointer we were given BD FFFFFFFF # LOADI32_EBP %-1 ; Our flag for byte processing BE 00000000 # LOADI32_ESI %0 ; temp storage for the sum BF 00000000 # LOADI32_EDI %0 ; Our starting IP E8 %a # CALLI32 %First_pass ; Process it ; rewind input file 8B1D A9820408 # LOAD32_Absolute32_ebx &fin ; Using our input file B9 00000000 # LOADI32_ECX %0 ; Offset Zero BA 00000000 # LOADI32_EDX %0 ; Whence Zero B8 13000000 # LOADI32_EAX %19 ; lseek CD80 # INT_80 BD FFFFFFFF # LOADI32_EBP %-1 ; Our flag for byte processing BE 00000000 # LOADI32_ESI %0 ; temp storage for the sum BF 00000000 # LOADI32_EDI %0 ; Our starting IP E8 %g # CALLI32 %Second_pass ; Process it E9 %s # JMP32 %Done :a #:First_pass E8 %t # CALLI32 %Read_byte ; Deal with EOF 83F8 FC # CMPI8_EAX !-4 0F84 %e # JE32 %First_pass_done ; Check for : 83F8 3A # CMPI8_EAX !58 0F85 %b # JNE32 %First_pass_0 ; Deal with label E8 %x # CALLI32 %StoreLabel :b #:First_pass_0 ; Check for : 83F8 25 # CMPI8_EAX !37 0F84 %d # JE32 %First_pass_pointer ; Deal with everything else E8 %f # CALLI32 %hex ; Process our char ; Deal with EOF 83F8 FC # CMPI8_EAX !-4 0F84 %e # JE32 %First_pass_done ; deal with -1 values 83F8 00 # CMPI8_EAX !0 0F8C %a # JL32 %First_pass ; deal with toggle 83FD 00 # CMPI8_EBP !0 0F84 %c # JE32 %First_pass_1 83C7 01 # ADDI8_EDI !1 ; Increment IP :c #:First_pass_1 F7D5 # NOT_EBP E9 %a # JMP32 %First_pass :d #:First_pass_pointer ; Deal with Pointer to label E8 %t # CALLI32 %Read_byte ; Drop the char 83C7 04 # ADDI8_EDI !4 ; Increment IP E9 %a # JMP32 %First_pass ; Loop again :e #:First_pass_done C3 # RET :f #:hex ; deal with EOF 83F8 FC # CMPI8_EAX !-4 0F84 %k # JE32 %EOF ; deal with line comments starting with ; 83F8 23 # CMPI8_EAX !35 0F84 %p # JE32 %ascii_comment ; deal with line comments starting with ; 83F8 3B # CMPI8_EAX !59 0F84 %p # JE32 %ascii_comment ; deal all ascii less than 0 83F8 30 # CMPI8_EAX !48 0F8C %o # JL32 %ascii_other ; deal with 0-9 83F8 3A # CMPI8_EAX !58 0F8C %l # JL32 %ascii_num ; deal with all ascii less than A 83F8 41 # CMPI8_EAX !65 0F8C %o # JL32 %ascii_other ; deal with A-F 83F8 47 # CMPI8_EAX !71 0F8C %n # JL32 %ascii_high ;deal with all ascii less than a 83F8 61 # CMPI8_EAX !97 0F8C %o # JL32 %ascii_other ;deal with a-f 83F8 67 # CMPI8_EAX !103 0F8C %m # JL32 %ascii_low ; The rest that remains needs to be ignored E9 %o # JMP32 %ascii_other :g #:Second_pass E8 %t # CALLI32 %Read_byte ; Deal with EOF 83F8 FC # CMPI8_EAX !-4 0F84 %j # JE32 %Second_pass_done ; Simply drop the label 83F8 3A # CMPI8_EAX !58 0F85 %h # JNE32 %Second_pass_0 E8 %t # CALLI32 %Read_byte E9 %g # JMP32 %Second_pass :h #:Second_pass_0 ; Deal with pointer 83F8 25 # CMPI8_EAX !37 0F85 %i # JNE32 %Second_pass_1 E8 %y # CALLI32 %StorePointer E9 %g # JMP32 %Second_pass :i #:Second_pass_1 ; Deal with everything else E8 %f # CALLI32 %hex ; Process our char ; Deal with EOF 83F8 FC # CMPI8_EAX !-4 0F84 %j # JE32 %Second_pass_done ; deal with -1 values 83F8 00 # CMPI8_EAX !0 0F8C %g # JL32 %Second_pass ; deal with toggle 83FD 00 # CMPI8_EBP !0 0F84 %r # JE32 %print ; process first byte of pair 89C6 # COPY_EAX_to_ESI BD 00000000 # LOADI32_EBP %0 E9 %g # JMP32 %Second_pass :j #:Second_pass_done C3 # RET :k #:EOF C3 # RET :l #:ascii_num 83E8 30 # SUBI8_EAX !48 C3 # RET :m #:ascii_low 83E8 57 # SUBI8_EAX !87 C3 # RET :n #:ascii_high 83E8 37 # SUBI8_EAX !55 C3 # RET :o # :ascii_other B8 FFFFFFFF # LOADI32_EAX %-1 C3 # RET :p #:ascii_comment E8 %t # CALLI32 %Read_byte 83F8 0D # CMPI8_EAX !13 0F84 %q # JE32 %ascii_comment_cr 83F8 0A # CMPI8_EAX !10 0F85 %p # JNE32 %ascii_comment :q #:ascii_comment_cr B8 FFFFFFFF # LOADI32_EAX %-1 C3 # RET ; process second byte of pair :r #:print ; update the sum and store in output C1E6 04 # SHLI8_ESI !4 01F0 # ADD_ESI_to_EAX A2 B1820408 # STORE8_Absolute32_al &table ; flip the toggle F7D5 # NOT_EBP ; Print our first Hex BA 01000000 # LOADI32_EDX %1 ; set the size of chars we want E8 %v # CALLI32 %print_chars 83C7 01 # ADDI8_EDI !1 ; Increment IP E9 %g # JMP32 %Second_pass :s #:Done ; program completed Successfully BB 00000000 # LOADI32_EBX %0 ; All is well B8 01000000 # LOADI32_EAX %1 ; put the exit syscall number in eax CD80 # INT_80 ; Call it a good day :t #:Read_byte ; Attempt to read 1 byte from STDIN BA 01000000 # LOADI32_EDX %1 ; set the size of chars we want B9 B1820408 # LOADI32_ECX &table ; Where to put it 8B1D A9820408 # LOAD32_Absolute32_ebx &fin ; Where are we reading from B8 03000000 # LOADI32_EAX %3 ; the syscall number for read CD80 # INT_80 ; call the Kernel 85C0 # TEST ; check what we got 0F84 %u # JE32 %Read_byte_1 ; Got EOF call it done ; load byte A0 B1820408 # LOAD8_Absolute32_al &table ; load char 0FB6C0 # MOVZX ; We have to zero extend it to use it C3 # RET ; Deal with EOF :u #:Read_byte_1 B8 FCFFFFFF # LOADI32_EAX %-4 ; Put EOF in eax C3 # RET :v #:print_chars B9 B1820408 # LOADI32_ECX &table ; What we are writing 8B1D AD820408 # LOAD32_Absolute32_ebx &fout ; Write to target file B8 04000000 # LOADI32_EAX %4 ; the syscall number for write CD80 # INT_80 ; call the Kernel C3 # RET :w #:Get_table_target E8 %t # CALLI32 %Read_byte ; Get single char label C1E0 02 # SHLI8_EAX !2 ; Each label in table takes 4 bytes to store 05 B1820408 # ADDI32_EAX &table ; Calculate offset C3 # RET :x #:StoreLabel E8 %w # CALLI32 %Get_table_target 8938 # STORE32_EDI_into_Address_EAX ; Write out pointer to table C3 # RET :y #:StorePointer 83C7 04 # ADDI8_EDI !4 ; Increment IP E8 %w # CALLI32 %Get_table_target ; Get address of pointer 8B00 # LOAD32_Address_EAX_into_EAX ; Get pointer 29F8 # SUB_EDI_from_EAX ; target - ip A3 B1820408 # STORE32_Absolute32_eax &table ; put value in output BA 04000000 # LOADI32_EDX %4 ; set the size of chars we want E8 %v # CALLI32 %print_chars C3 # RET #:fin 00000000 # NULL #:fout 00000000 # NULL #:table #:ELF_end