path: root/subx/ex6.subx

## print out a (global variable) string to stdout
#
# To run:
#   $ subx translate ex6.subx ex6
#   $ subx run ex6
#   Hello, world!

== 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

  ## write(stdout, x, 1)
  # fd = 1 (stdout)
  bb                                                                                                                      1/imm32           # copy 1 to EBX
  # set location to write out
  b9                                                                                                                      0x08049097/imm32  # copy to ECX
  # set size
  ba                                                                                                                      0x08049093/imm32  # copy to EDX
  8b                              0/mod/indirect  2/rm32/edx                                  2/r32/edx                                     # copy *EDX to EDX
  # syscall = write
  b8                                                                                                                      4/imm32           # copy 4 to EAX
  # call
  cd                                                                                                                      0x80/imm8         # int 80h

  ## exit(EBX)
  b8                                                                                                                      1/imm32           # copy 1 to EAX
  cd                                                                                                                      0x80/imm8         # int 80h

== 0x08049093
# size of string
0e 00 00 00
# string
  48 65 6c 6c 6f 2c 20 77 6f 72 6c 64 21 0a
# h  e  l  l  o  ,  ␣  w  o  r  l  d  !  newline

# vim:ft=subx:nowrap