## read a character from stdin, save it to a global, write it to stdout # # To run: # $ subx translate ex4.subx ex4 # $ subx run ex4 == 0x08048074 # code segment, after leaving room for ELF header and segment headers # instruction effective address operand displacement immediate # op subop mod rm32 base index scale r32 # 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes ## read(stdin, x, 1) # fd = 0 (stdin) bb/copy 0/imm32 # copy 0 to EBX # initialize x (location to write result to) b9/copy 0x080490a7/imm32 # copy to ECX # size = 1 character ba/copy 1/imm32 # copy 1 to EDX # read(fd, x, size) b8/copy 3/imm32 # copy 3 to EAX cd/syscall 0x80/imm8 # int 80h ## write(stdout, x, 1) # fd = 1 (stdout) bb/copy 1/imm32 # copy 1 to EBX # initialize x (location to read from) b9/copy 0x080490a7/imm32 # copy to ECX # size = 1 character ba/copy 1/imm32 # copy 1 to EDX # write(fd, x, size) b8/copy 4/imm32 # copy 4 to EAX cd/syscall 0x80/imm8 # int 80h ## exit(EBX) b8/copy 1/imm32 # copy 1 to EAX cd/syscall 0x80/imm8 # int 80h == 0x080490a7 # data segment 00 00 00 00 # space for read() to write to # vim:ft=subx:nowrap