diffmaps.script.py

# Script to be used with gdb to trace changes to the maps file as Node.js
# performs mmaps.

import io
import os
import sys
import gdb
import shutil
import subprocess

class DiffMaps (gdb.Command):
  "Compare maps file to previous run of the command"

  def __init__(self):
    super(DiffMaps, self).__init__(
      "diffmaps",
      gdb.COMMAND_RUNNING,
      gdb.COMPLETE_NONE,
      True)

  def invoke(self, arg, from_tty):
    orig = arg + "/000.maps"
    new = arg + "/001.maps"
    maps_file = "/proc/" + str(gdb.selected_inferior().pid) + "/maps"

    # If this is the first time, the diff must be the whole original file.
    if not os.path.isfile(orig):
      io.open(orig, "w").close()

    shutil.copyfile(maps_file, new)

    diff = subprocess.Popen(["diff", "-u", orig, new])
    diff.wait()
    shutil.copyfile(new, orig)
    gdb.flush()
DiffMaps()

gdb.script

set pagination off
set breakpoint pending on
set style enabled off
set environment NODE_ENV=production
source /home/nix/node-dtlb/run-ghost/scripts/diffmaps.script.py
define domaps
shell echo "*** Start Event ***"
shell echo "*** Initial diff **"
diffmaps /home/nix/node-dtlb/Ghost
shell echo "*******************"
bt 10
python gdb.execute('finish');
shell echo "*** Final diff ****"
diffmaps /home/nix/node-dtlb/Ghost
shell echo "*******************"
shell echo "*** End Event *****"
continue
end
start ./current/index
break mmap
commands
domaps
end
break munmap
commands
domaps
end
break mremap
commands
domaps
end
break madvise
commands
domaps
end
break mprotect
commands
domaps
end
continue