# >>>>>>>>>>>>> ELF FILE HEADER <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< # All numbers (except in names) are in base sixteen (hexadecimal) # 00 <- number of bytes listed so far 7F 45 4C 46 # 04 e_ident[EI_MAG]: ELF magic number 01 # 05 e_ident[EI_CLASS]: 1: 32-bit, 2: 64-bit 01 # 06 e_ident[EI_DATA]: 1: little-endian, 2: big-endian 01 # 07 e_ident[EI_VERSION]: ELF header version; must be 1 00 # 08 e_ident[EI_OSABI]: Target OS ABI; should be 0 00 # 09 e_ident[EI_ABIVERSION]: ABI version; 0 is ok for Linux 00 00 00 # 0C e_ident[EI_PAD]: unused, should be 0 00 00 00 00 # 10 02 00 # 12 e_type: object file type; 2: executable 03 00 # 14 e_machine: instruction set architecture; 3: x86, 3E: amd64 01 00 00 00 # 18 e_version: ELF identification version; must be 1 82 80 04 08 # 1C e_entry: memory address of entry point (where process starts) 34 00 00 00 # 20 e_phoff: file offset where program headers begin 00 00 00 00 # 24 e_shoff: file offset where section headers begin 00 00 00 00 # 28 e_flags: 0 for x86 34 00 # 2A e_ehsize: size of this header (34: 32-bit, 40: 64-bit) 20 00 # 2C e_phentsize: size of each program header (20: 32-bit, 38: 64-bit) 01 00 # 2E e_phnum: #program headers 28 00 # 30 e_shentsize: size of each section header (28: 32-bit, 40: 64-bit) 00 00 # 32 e_shnum: #section headers 00 00 # 34 e_shstrndx: index of section header containing section names # >>>>>>>>>>>>> ELF PROGRAM HEADER <<<<<<<<<<<<<<<<<<<<<<<< 01 00 00 00 # 38 p_type: segment type; 1: loadable 00 00 00 00 # 3C p_offset: file offset where segment begins 00 80 04 08 # 40 p_vaddr: virtual address of segment in memory (x86: 08048000) 00 00 00 00 # 44 p_paddr: physical address of segment, unspecified by 386 supplement 15 01 00 00 # 48 p_filesz: size in bytes of the segment in the file image ############ 00 80 FB 77 # 4C p_memsz: size in bytes of the segment in memory; p_filesz <= p_memsz 07 00 00 00 # 50 p_flags: segment-dependent flags (1: X, 2: W, 4: R) 00 10 00 00 # 54 p_align: 1000 for x86 # >>>>>>>>>>>>> PROGRAM SEGMENT <<<<<<<<<<<<< #### LIBRARY #### # INTENTION INSTRUCTION OPCODE NOTE # PutOut: # ECX=obuf EDX=count 54 -- <0:err =0:ok EAX=stat ECX=? EDX=? EBX=1 31 DB 43 # ebx = 1 (stdout) xor r/m32, r32; inc 31 /r 11 011 011 # .flush: # 57 8D 43 03 # eax = ebx + 3 (write) lea r32, m 8D /r 01 000 011 CD 80 # syscall int imm8 CD ib 85 C0 # cmp eax, 0 test r/m32, r32 85 /r 11 000 000 7C 06 # jump .ret if < 60 jl rel8 7C cb 01 C1 # ecx += eax add r/m32, r32 01 /r 11 000 001 29 C2 # edx -= eax sub r/m32, r32 29 /r 11 000 010 7F F1 # jump .flush if > 66 jg rel8 7F cb # .ret: 66 C3 # return ret C3 # To use input, reserve ESI and EBP. Set EBP=0 before first use. Byte -> [ESI], each call. # TakeIn: # ECX=ibuf EDX=count 67 -- <0:err =0:done >0:ok EAX=? EBX=0(if err) 46 # esi++ inc r32 40+rd 4D # ebp-- dec r32 48+rd 7F 0D # jump .ret if > 6B jg rel8 7F cb 31 DB # ebx = 0 (stdin) xor r/m32, r32 31 /r 11 011 011 8D 43 03 # eax = 3 (read) lea r32, m 8D /r 01 000 011 CD 80 # syscall int imm8 CD ib 85 C0 # cmp eax, 0 test r/m32, r32 85 /r 11 000 000 89 CE # esi = ecx mov r/m32, r32 89 /r 11 001 110 89 C5 # ebp = eax mov r/m32, r32 89 /r 11 000 101 # .ret: 78 C3 # return ret C3 # Exit-1: 79 4B # ebx-- dec r32 48+rd # Exit: # EBX=stat -- 7A 31 C0 40 # eax = 1 (exit) xor r/m32, r32; inc 31 /r 11 000 000 CD 80 # syscall int imm8 CD ib # Exit+1: 7F 43 # ebx++ inc r32 40+rd EB F8 # jump Exit 82 jmp rel8 EB cb # 08048000 = Head # ecx: 20000000 = ibuf = ilen # 40000000 = obuf = olen # 80000000 > seg # al: char # ebx: acc # ebp: num chars available in ibuf # esi: input pointer (address in memory) # edi: output pointer (file pos from 0) #### COMPILER ### # CopyHeader: # 82 <-- Entry point for this and compiled programs 31 ED # ebp = 0 xor r/m32, r32 31 /r 11 101 101 31 C9 # ecx = 0 xor r/m32, r32 31 /r 11 001 001 B1 82 # ecx = len (header) mov r8, imm8 B0+rb ib BE 00 80 04 08 # esi = Head mov r32, imm32 B8+rd id BF 00 00 00 20 # edi = ibuf mov r32, imm32 B8+rd id 51 57 # push ecx, edi push r32 50+rd S: len ibuf 01 FF # edi = obuf (=edi+edi) add r/m32, r32 01 /r 11 111 111 F3 A4 # copy string rep movs m8, m8 F3 A4 59 5F # ecx = ibuf, edi = len pop r32 58+rd S: EB 24 # jump Record 9C jmp rel8 EB cb # GetByte: # ECX=ibuf -- 9C 53 # push ebx push r32 50+rd S: acc 89 CA # edx = ecx mov r/m32, r32 89 /r 11 001 010 E8 C3 FF FF FF # call TakeIn A4 call rel32 E8 cb 7C D3 # jump Exit+1 if < A6 jl rel8 7C cb 5B # pop ebx pop r32 58+rd S: 7E 03 # jump Finish if <= A9 jle rel8 7E cb 8A 06 # al = [esi] mov r8, r/m8 8A /r 00 000 110 C3 # return ret C3 # Finish: # ECX=ibuf AC 01 C9 # ecx = obuf (=ecx+ecx) add r/m32, r32 01 /r 11 001 001 8B 51 44 # edx = [ecx+44] mov r32, r/m32 8B /r 01 010 001 E8 9E FF FF FF # call PutOut B6 call rel32 E8 cb 7C C7 # jump Exit+1 if < B8 jl rel8 7C cb EB BF # jump Exit-1 BA jmp rel8 EB cb # WORD: BA 39 7C 09 44 # cmp [2*ecx+44], edi cmp r/m32, r32 39 /r 01 111 100 00 001 001 7D 04 # jump Clear if >= C0 jge rel8 7D cb # Record: C0 89 7C 09 44 # [2*ecx+44] = edi mov r/m32, r32 89 /r 01 111 100 00 001 001 # Clear: # null: 80000000 C4 6B D9 04 # ebx = ecx * 4 imul r32, r/m32, imm8 6B /r ib 11 011 001 # CHAR: C7 E8 D0 FF FF FF # call GetByte CC call rel32 E8 cd # Hash: 3C 23 # cmp al, '#' cmp al, imm8 3C ib 7C 0B # jump WhSpace if < D0 jl rel8 7C cb 7F 13 # jump Op if > D2 jg rel8 7F cb # Comment: D2 E8 C5 FF FF FF # call GetByte D7 call rel32 E8 cd 3C 0A # cmp al, '\n' cmp al, imm8 3C ib 75 F7 # jump Comment if != DB jne rel8 75 cb # WhSpace: DB 85 DB # cmp ebx, 0 test r/m32, r32 85 /r 11 011 011 7C DB # jump WORD if < DF jl rel8 7C cb 88 1C 4F # [2*ecx+edi] = bl mov r/m8, r8 88 /r 00 011 100 01 001 111 47 # edi++ inc r32 40+rd EB D5 # jump WORD E5 jmp rel8 EB cb # Op: E5 ASCII summary: \t\n #+-0:A 3C 2D # cmp al, '-' cmp al, imm8 3C ib 74 25 # jump Minus if == E9 je rel8 74 cb 7C 15 # jump Plus if < EB jl rel8 7C cb 3C 3A # cmp al, ':' 74 0D # jump Colon if == EF je rel8 74 cb 7C 02 # jump Digit if < F1 jl rel8 7C cb # Letter: 2C 07 # al -= 'A'-'0'-A sub al, imm8 2C ib # Digit: F3 2C 30 # al -= '0' sub al, imm8 2C ib C1 E3 04 # ebx <<= 4 shl r/m32, imm8 C1 /4 ib 11 100 011 00 C3 # bl += al add r/m8, r8 00 /r 11 000 011 EB CB # jump CHAR FC jmp rel8 EB cb # Colon: FC 89 DF # edi = ebx mov r/m32, r32 89 /r 11 011 111 EB BA # jump WORD 100 jmp rel8 EB cb # Plus: 100 81 C3 00 80 04 08 # ebx += Head add r/m32, imm32 81 /0 id 11 000 011 # Append: 106 89 1C 4F # [2*ecx+edi] = ebx mov r/m32, r32 89 /r 00 011 100 01 001 111 83 C7 04 # edi += 4 add r/m32, imm8 83 /0 ib 11 000 111 EB AC # jump WORD 10E jmp rel8 EB cb # Minus: 10E 83 EB 04 # ebx -= 4 sub r/m32, imm8 83 /5 ib 11 101 011 29 FB # ebx -= edi sub r/m32, r32 29 /r 11 111 011 EB F1 # jump Append 115 jmp rel8 EB cb