#!/usr/bin/env vpython # Copyright 2013 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. """Patch an orderfile. Starting with a list of symbols in a binary and an orderfile (ordered list of symbols), matches the symbols in the orderfile and augments each symbol with the symbols residing at the same address (due to having identical code). The output is a list of symbols appropriate for the linker option --symbol-ordering-file for lld. Note this is not usable with gold (which uses section names to order the binary). Note: It is possible to have. - Several symbols mapping to the same offset in the binary. - Several offsets for a given symbol (because we strip the ".clone." and other suffixes) The general pipeline is: 1. Get the symbol infos (name, offset, size, section) from the binary 2. Get the symbol names from the orderfile 3. Find the orderfile symbol names in the symbols coming from the binary 4. For each symbol found, get all the symbols at the same address 5. Output them to an updated orderfile suitable lld """ import argparse import collections import logging import re import sys import symbol_extractor # Suffixes for symbols. These are due to method splitting for inlining and # method cloning for various reasons including constant propagation and # inter-procedural optimization. _SUFFIXES = ('.clone.', '.part.', '.isra.', '.constprop.') # The pattern and format for a linker-generated outlined function. _OUTLINED_FUNCTION_RE = re.compile(r'OUTLINED_FUNCTION_(?P\d+)$') _OUTLINED_FUNCTION_FORMAT = 'OUTLINED_FUNCTION_{}' def RemoveSuffixes(name): """Strips method name suffixes from cloning and splitting. .clone. comes from cloning in -O3. .part. comes from partial method splitting for inlining. .isra. comes from inter-procedural optimizations. .constprop. is cloning for constant propagation. """ for suffix in _SUFFIXES: name = name.split(suffix)[0] return name def _UniqueGenerator(generator): """Converts a generator to skip yielding elements already seen. Example: @_UniqueGenerator def Foo(): yield 1 yield 2 yield 1 yield 3 Foo() yields 1,2,3. """ def _FilteringFunction(*args, **kwargs): returned = set() for item in generator(*args, **kwargs): if item in returned: continue returned.add(item) yield item return _FilteringFunction def _GroupSymbolsByOffset(binary_filename): """Produce a map symbol name -> all symbol names at same offset. Suffixes are stripped. """ symbol_infos = [ s._replace(name=RemoveSuffixes(s.name)) for s in symbol_extractor.SymbolInfosFromBinary(binary_filename)] offset_map = symbol_extractor.GroupSymbolInfosByOffset(symbol_infos) missing_offsets = 0 sym_to_matching = {} for sym in symbol_infos: if sym.offset not in offset_map: missing_offsets += 1 continue matching = [s.name for s in offset_map[sym.offset]] assert sym.name in matching sym_to_matching[sym.name] = matching return sym_to_matching def _GetMaxOutlinedIndex(sym_dict): """Find the largest index of an outlined functions. See _OUTLINED_FUNCTION_RE for the definition of the index. In practice the maximum index equals the total number of outlined functions. This function asserts that the index is near the total number of outlined functions. Args: sym_dict: Dict with symbol names as keys. Returns: The largest index of an outlined function seen in the keys of |sym_dict|. """ seen = set() for sym in sym_dict: m = _OUTLINED_FUNCTION_RE.match(sym) if m: seen.add(int(m.group('index'))) if not seen: return None max_index = max(seen) # Assert that the number of outlined functions is reasonable compared to the # indices we've seen. At the time of writing, outlined functions are indexed # consecutively from 0. If this radically changes, then other outlining # behavior may have changed to violate some assumptions. assert max_index < 2 * len(seen) return max_index def _StripSuffixes(section_list): """Remove all suffixes on items in a list of symbols.""" return [RemoveSuffixes(section) for section in section_list] def _PatchedSymbols(symbol_to_matching, profiled_symbols, max_outlined_index): """Internal computation of an orderfile. Args: symbol_to_matching: ({symbol name -> [symbols at same offset]}), as from _GroupSymbolsByOffset. profiled_symbols: ([symbol names]) as from the unpatched orderfile. max_outlined_index: (int or None) if not None, add outlined function names to the end of the patched orderfile. Yields: Patched symbols, in a consistent order to profiled_symbols. """ missing_symbol_count = 0 seen_symbols = set() for sym in profiled_symbols: if _OUTLINED_FUNCTION_RE.match(sym): continue if sym in seen_symbols: continue if sym not in symbol_to_matching: missing_symbol_count += 1 continue for matching in symbol_to_matching[sym]: if matching in seen_symbols: continue if _OUTLINED_FUNCTION_RE.match(matching): continue yield matching seen_symbols.add(matching) assert sym in seen_symbols logging.warning('missing symbol count = %d', missing_symbol_count) if max_outlined_index is not None: # The number of outlined functions may change with each build, so only # ordering the outlined functions currently in the binary will not # guarantee ordering after code changes before the next orderfile is # generated. So we double the number of outlined functions as a measure of # security. for idx in xrange(2 * max_outlined_index + 1): yield _OUTLINED_FUNCTION_FORMAT.format(idx) @_UniqueGenerator def ReadOrderfile(orderfile): """Reads an orderfile and cleans up symbols. Args: orderfile: The name of the orderfile. Yields: Symbol names, cleaned and unique. """ with open(orderfile) as f: for line in f.xreadlines(): line = line.strip() if line: yield line def GeneratePatchedOrderfile(unpatched_orderfile, native_lib_filename, output_filename, order_outlined=False): """Writes a patched orderfile. Args: unpatched_orderfile: (str) Path to the unpatched orderfile. native_lib_filename: (str) Path to the native library. output_filename: (str) Path to the patched orderfile. order_outlined: (bool) If outlined function symbols are present in the native library, then add ordering of them to the orderfile. If there are no outlined function symbols present then this flag has no effect. """ symbol_to_matching = _GroupSymbolsByOffset(native_lib_filename) if order_outlined: max_outlined_index = _GetMaxOutlinedIndex(symbol_to_matching) if not max_outlined_index: # Only generate ordered outlined functions if they already appeared in # the library. max_outlined_index = None else: max_outlined_index = None # Ignore outlining. profiled_symbols = ReadOrderfile(unpatched_orderfile) with open(output_filename, 'w') as f: # Make sure the anchor functions are located in the right place, here and # after everything else. # See the comment in //base/android/library_loader/anchor_functions.cc. # # __cxx_global_var_init is one of the largest symbols (~38kB as of May # 2018), called extremely early, and not instrumented. for first_section in ('dummy_function_start_of_ordered_text', '__cxx_global_var_init'): f.write(first_section + '\n') for sym in _PatchedSymbols(symbol_to_matching, profiled_symbols, max_outlined_index): f.write(sym + '\n') f.write('dummy_function_end_of_ordered_text\n') def _CreateArgumentParser(): """Creates and returns the argument parser.""" parser = argparse.ArgumentParser() parser.add_argument('--target-arch', action='store', default='arm', choices=['arm', 'arm64', 'x86', 'x86_64', 'x64', 'mips'], help='The target architecture for the library.') parser.add_argument('--unpatched-orderfile', required=True, help='Path to the unpatched orderfile') parser.add_argument('--native-library', required=True, help='Path to the native library') parser.add_argument('--output-file', required=True, help='Output filename') return parser def main(): parser = _CreateArgumentParser() options = parser.parse_args() symbol_extractor.SetArchitecture(options.target_arch) GeneratePatchedOrderfile(options.unpatched_orderfile, options.native_library, options.output_file) return 0 if __name__ == '__main__': logging.basicConfig(level=logging.INFO) sys.exit(main())