utils/indirect_calls.py

   1 #!/usr/bin/env python
   2
   3 """A tool for looking for indirect jumps and calls in x86 binaries.
   4
   5    Helpful to verify whether or not retpoline mitigations are catching
   6    all of the indirect branches in a binary and telling you which
   7    functions the remaining ones are in (assembly, etc).
   8
   9    Depends on llvm-objdump being in your path and is tied to the
  10    dump format.
  11 """
  12
  13 from __future__ import print_function
  14
  15 import os
  16 import sys
  17 import re
  18 import subprocess
  19 import optparse
  20
  21 # Look for indirect calls/jmps in a binary. re: (call|jmp).*\*
  22 def look_for_indirect(file):
  23     args = ['llvm-objdump']
  24     args.extend(["-d"])
  25     args.extend([file])
  26
  27     p = subprocess.Popen(args=args, stdin=None, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
  28     (stdout,stderr) = p.communicate()
  29
  30     function = ""
  31     for line in stdout.splitlines():
  32         if line.startswith(' ') == False:
  33             function = line
  34         result = re.search('(call|jmp).*\*', line)
  35         if result != None:
  36             # TODO: Perhaps use cxxfilt to demangle functions?
  37             print(function)
  38             print(line)
  39     return
  40
  41 def main(args):
  42     # No options currently other than the binary.
  43     parser = optparse.OptionParser("%prog [options] <binary>")
  44     (opts, args) = parser.parse_args(args)
  45     if len(args) != 2:
  46         parser.error("invalid number of arguments: %s" % len(args))
  47     look_for_indirect(args[1])
  48
  49 if __name__ == '__main__':
  50     main(sys.argv)