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#!/usr/bin/env python
# Copyright (c) 2012 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Dump functions called by static intializers in a Linux Release binary.
Usage example:
tools/linux/dump-static-intializers.py out/Release/chrome
A brief overview of static initialization:
1) the compiler writes out, per object file, a function that contains
the static intializers for that file.
2) the compiler also writes out a pointer to that function in a special
section.
3) at link time, the linker concatenates the function pointer sections
into a single list of all initializers.
4) at run time, on startup the binary runs all function pointers.
The functions in (1) all have mangled names of the form
_GLOBAL__I_foobar.cc
using objdump, we can disassemble those functions and dump all symbols that
they reference.
"""
import optparse
import re
import subprocess
import sys
# A map of symbol => informative text about it.
NOTES = {
'__cxa_atexit@plt': 'registers a dtor to run at exit',
'std::__ioinit': '#includes <iostream>, use <ostream> instead',
}
class Demangler(object):
"""A wrapper around c++filt to provide a function to demangle symbols."""
def __init__(self):
self.cppfilt = subprocess.Popen(['c++filt'],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE)
def Demangle(self, sym):
"""Given mangled symbol |sym|, return its demangled form."""
self.cppfilt.stdin.write(sym + '\n')
return self.cppfilt.stdout.readline().strip()
# Matches for example: "cert_logger.pb.cc", capturing "cert_logger".
protobuf_filename_re = re.compile(r'(.*)\.pb\.cc$')
def QualifyFilenameAsProto(filename):
"""Attempt to qualify a bare |filename| with a src-relative path, assuming it
is a protoc-generated file. If a single match is found, it is returned.
Otherwise the original filename is returned."""
match = protobuf_filename_re.match(filename)
if not match:
return filename
basename = match.groups(0)
gitlsfiles = subprocess.Popen(
['git', 'ls-files', '--', '*/%s.proto' % basename],
stdout=subprocess.PIPE)
candidate = filename
for line in gitlsfiles.stdout:
if candidate != filename:
return filename # Multiple hits, can't help.
candidate = line.strip()
return candidate
# Regex matching the substring of a symbol's demangled text representation most
# likely to appear in a source file.
# Example: "v8::internal::Builtins::InitBuiltinFunctionTable()" becomes
# "InitBuiltinFunctionTable", since the first (optional & non-capturing) group
# picks up any ::-qualification and the last fragment picks up a suffix that
# starts with an opener.
symbol_code_name_re = re.compile(r'^(?:[^(<[]*::)?([^:(<[]*).*?$')
def QualifyFilename(filename, symbol):
"""Given a bare filename and a symbol that occurs in it, attempt to qualify
it with a src-relative path. If more than one file matches, return the
original filename."""
match = symbol_code_name_re.match(symbol)
if not match:
return filename
symbol = match.group(1)
gitgrep = subprocess.Popen(
['git', 'grep', '-l', symbol, '--', '*/%s' % filename],
stdout=subprocess.PIPE)
candidate = filename
for line in gitgrep.stdout:
if candidate != filename: # More than one candidate; return bare filename.
return filename
candidate = line.strip()
return candidate
# Regex matching nm output for the symbols we're interested in.
# Example line:
# 0000000001919920 0000000000000008 t _ZN12_GLOBAL__I_safe_browsing_service.cc
nm_re = re.compile(r'(\S+) (\S+) t _GLOBAL__I_(.*)')
def ParseNm(binary):
"""Given a binary, yield static initializers as (file, start, size) tuples."""
nm = subprocess.Popen(['nm', '-S', binary], stdout=subprocess.PIPE)
for line in nm.stdout:
match = nm_re.match(line)
if match:
addr, size, filename = match.groups()
yield filename, int(addr, 16), int(size, 16)
# Regex matching objdump output for the symbols we're interested in.
# Example line:
# 12354ab: (disassembly, including <FunctionReference>)
disassembly_re = re.compile(r'^\s+[0-9a-f]+:.*<(\S+)>')
def ExtractSymbolReferences(binary, start, end):
"""Given a span of addresses, returns symbol references from disassembly."""
cmd = ['objdump', binary, '--disassemble',
'--start-address=0x%x' % start, '--stop-address=0x%x' % end]
objdump = subprocess.Popen(cmd, stdout=subprocess.PIPE)
refs = set()
for line in objdump.stdout:
if '__static_initialization_and_destruction' in line:
raise RuntimeError, ('code mentions '
'__static_initialization_and_destruction; '
'did you accidentally run this on a Debug binary?')
match = disassembly_re.search(line)
if match:
(ref,) = match.groups()
if ref.startswith('.LC') or ref.startswith('_DYNAMIC'):
# Ignore these, they are uninformative.
continue
if ref.startswith('_GLOBAL__I_'):
# Probably a relative jump within this function.
continue
refs.add(ref)
return sorted(refs)
def main():
parser = optparse.OptionParser(usage='%prog [option] filename')
parser.add_option('-d', '--diffable', dest='diffable',
action='store_true', default=False,
help='Prints the filename on each line, for more easily '
'diff-able output.')
opts, args = parser.parse_args()
if len(args) != 1:
parser.error('missing filename argument')
return 1
binary = args[0]
demangler = Demangler()
file_count = 0
initializer_count = 0
files = ParseNm(binary)
if opts.diffable:
files = sorted(files)
for filename, addr, size in files:
if size == 2:
# gcc generates a two-byte 'repz retq' initializer when there is nothing
# to do. jyasskin tells me this is fixed in gcc 4.6.
continue
file_count += 1
ref_output = []
qualified_filename = QualifyFilenameAsProto(filename)
for ref in ExtractSymbolReferences(binary, addr, addr+size):
initializer_count += 1
ref = demangler.Demangle(ref)
if qualified_filename == filename:
qualified_filename = QualifyFilename(filename, ref)
if ref in NOTES:
ref_output.append(' %s [%s]' % (ref, NOTES[ref]))
else:
ref_output.append(' ' + ref)
if opts.diffable:
print '\n'.join(qualified_filename + r for r in ref_output)
else:
print '%s (initializer offset 0x%x size 0x%x)' % (qualified_filename,
addr, size)
print '\n'.join(ref_output) + '\n'
print 'Found %d static initializers in %d files.' % (initializer_count,
file_count)
return 0
if '__main__' == __name__:
sys.exit(main())
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