1#!/usr/bin/env python 2from __future__ import print_function 3''' 4Helper script to print out the raw content of an ELF section. 5Example usages: 6``` 7# print out as bits by default 8extract-section.py .text --input-file=foo.o 9``` 10``` 11# read from stdin and print out in hex 12cat foo.o | extract-section.py -h .text 13``` 14This is merely a wrapper around `llvm-readobj` that focuses on the binary 15content as well as providing more formatting options. 16''' 17 18# Unfortunately reading binary from stdin is not so trivial in Python... 19def read_raw_stdin(): 20 import sys 21 if sys.version_info >= (3, 0): 22 reading_source = sys.stdin.buffer 23 else: 24 # Windows will always read as string so we need some 25 # special handling 26 if sys.platform == 'win32': 27 import os, msvcrt 28 msvcrt.setformat(sys.stdin.fileno(), os.O_BINARY) 29 reading_source = sys.stdin 30 return reading_source.read() 31 32def get_raw_section_dump(readobj_path, section_name, input_file): 33 import subprocess 34 cmd = [readobj_path, '--elf-output-style=GNU', '--hex-dump={}'.format(section_name), 35 input_file] 36 proc = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE) 37 38 if input_file == '-': 39 # From stdin 40 out,_ = proc.communicate(input=read_raw_stdin()) 41 else: 42 out,_ = proc.communicate() 43 44 return out.decode('utf-8') if type(out) is not str else out 45 46if __name__ == '__main__': 47 import argparse 48 # The default '-h' (--help) will conflict with our '-h' (hex) format 49 arg_parser = argparse.ArgumentParser(add_help=False) 50 arg_parser.add_argument('--readobj-path', metavar='<executable path>', type=str, 51 help='Path to llvm-readobj') 52 arg_parser.add_argument('--input-file', metavar='<file>', type=str, 53 help='Input object file, or \'-\' to read from stdin') 54 arg_parser.add_argument('section', metavar='<name>', type=str, 55 help='Name of the section to extract') 56 # Output format 57 format_group = arg_parser.add_mutually_exclusive_group() 58 format_group.add_argument('-b', dest='format', action='store_const', const='bits', 59 help='Print out in bits') 60 arg_parser.add_argument('--byte-indicator', action='store_true', 61 help='Whether to print a \'.\' every 8 bits in bits printing mode') 62 arg_parser.add_argument('--bits-endian', metavar='<little/big>', type=str, 63 choices=['little', 'big'], 64 help='Print out bits in specified endianness (little or big); defaults to big') 65 format_group.add_argument('-h', dest='format', action='store_const', const='hex', 66 help='Print out in hexadecimal') 67 arg_parser.add_argument('--hex-width', metavar='<# of bytes>', type=int, 68 help='The width (in byte) of every element in hex printing mode') 69 70 arg_parser.add_argument('--help', action='help') 71 arg_parser.set_defaults(format='bits', tool_path='llvm-readobj', input_file='-', 72 byte_indicator=False, hex_width=4, bits_endian='big') 73 args = arg_parser.parse_args() 74 75 raw_section = get_raw_section_dump(args.tool_path, args.section, args.input_file) 76 77 results = [] 78 for line in raw_section.splitlines(False): 79 if line.startswith('Hex dump'): 80 continue 81 parts = line.strip().split(' ')[1:] 82 for part in parts[:4]: 83 # exclude any non-hex dump string 84 try: 85 val = int(part, 16) 86 if args.format == 'bits': 87 # divided into bytes first 88 offsets = (24, 16, 8, 0) 89 if args.bits_endian == 'little': 90 offsets = (0, 8, 16, 24) 91 for byte in [(val >> off) & 0xFF for off in offsets]: 92 for bit in [(byte >> off) & 1 for off in range(7, -1, -1)]: 93 results.append(str(bit)) 94 if args.byte_indicator: 95 results.append('.') 96 elif args.format == 'hex': 97 assert args.hex_width <= 4 and args.hex_width > 0 98 width_bits = args.hex_width * 8 99 offsets = [off for off in range(32 - width_bits, -1, -width_bits)] 100 mask = (1 << width_bits) - 1 101 format_str = "{:0" + str(args.hex_width * 2) + "x}" 102 for word in [(val >> i) & mask for i in offsets]: 103 results.append(format_str.format(word)) 104 except: 105 break 106 print(' '.join(results), end='') 107