Show disassembly of given opcodes or assembly instructions

nasm_shell.sh

#!/bin/bash
# See -h for help

INTERACTIVE=1
READ_ARGS=()
NASM_ARGS=()
OBJDUMP_ARGS=()

# Determine if interactive or stdin is redirected from file/heredoc/command
# output/etc
read -t 0 _
if [[ $? -eq 0 ]] ; then
  INTERACTIVE=0
  READ_ARGS=(-t 0.1)
fi

function usage {
  cat <<EOF
Usage "${BASH_SOURCE[0]}" [<options>]

Options:
  -f FORMAT  format, e.g. elf64
  -32        equivalent to -f elf32
  -64        equivalent to -f elf64
  -M SYNTAX  syntax, e.g. intel
  -m ARCH    architecture, e.g. arm

Example:
 "${BASH_SOURCE[0]}" -64 -M intel <<<'jmp rsp'
EOF
  exit 1
}

function disasm {
  local basef="${1}"
  nasm "${NASM_ARGS[@]}" "${basef}.nasm" -o "${basef}.o" || return $?
  objdump --no-addresses -d -j .text "${OBJDUMP_ARGS[@]}" "${basef}.o" | \
    sed '1,/^<\.text>/{d};s/^\s*//'
  rm "${basef}".o
}

function readin {
  # return 0 if more input expected (i.e. interactive and enter was pressed),
  # 1 otherwise
  local basef=$(mktemp opcode_to_asm.XXXXXXXX) line rc=1

  while IFS= read "${READ_ARGS[@]}" -r -p '> ' line ; do
    # quit on a blank line only in interactive mode
    if [ "${INTERACTIVE}" -eq 1 -a -z "${line}" ] ; then
     rc=0
     break
    fi
    echo -E "${line}" >> "${basef}.nasm"
  done

  if [ -f "${basef}.nasm" -a -s "${basef}.nasm" ] ; then
    disasm "${basef}"
    rm "${basef}".nasm
  fi

  return ${rc}
}

####################

while [ $# -gt 0 ] ; do
  case "${1}" in
    -32|-64)
      NASM_ARGS+=(-f "elf${1#-}")
      shift
      ;;
    -f)
      NASM_ARGS+=("${1}" "${2}")
      shift 2
      ;;
    -M|-m)
      OBJDUMP_ARGS+=("${1}" "${2}")
      shift 2
      ;;
    *)
      usage
      ;;
  esac
done

while readin ; do
  :
done