1 files changed, 538 insertions, 0 deletions
diff --git a/tools/check_elf_file.py b/tools/check_elf_file.py
new file mode 100755
index 0000000000..38c1cf4264
--- /dev/null
+++ b/tools/check_elf_file.py
@@ -0,0 +1,538 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2019 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""ELF file checker.
+
+This command ensures all undefined symbols in an ELF file can be resolved to
+global (or weak) symbols defined in shared objects specified in DT_NEEDED
+entries.
+"""
+
+from __future__ import print_function
+
+import argparse
+import collections
+import os
+import os.path
+import re
+import struct
+import subprocess
+import sys
+
+
+_ELF_MAGIC = b'\x7fELF'
+
+
+# Known machines
+_EM_386 = 3
+_EM_ARM = 40
+_EM_X86_64 = 62
+_EM_AARCH64 = 183
+
+_KNOWN_MACHINES = {_EM_386, _EM_ARM, _EM_X86_64, _EM_AARCH64}
+
+
+# ELF header struct
+_ELF_HEADER_STRUCT = (
+  ('ei_magic', '4s'),
+  ('ei_class', 'B'),
+  ('ei_data', 'B'),
+  ('ei_version', 'B'),
+  ('ei_osabi', 'B'),
+  ('ei_pad', '8s'),
+  ('e_type', 'H'),
+  ('e_machine', 'H'),
+  ('e_version', 'I'),
+)
+
+_ELF_HEADER_STRUCT_FMT = ''.join(_fmt for _, _fmt in _ELF_HEADER_STRUCT)
+
+
+ELFHeader = collections.namedtuple(
+  'ELFHeader', [_name for _name, _ in _ELF_HEADER_STRUCT])
+
+
+ELF = collections.namedtuple(
+  'ELF',
+  ('dt_soname', 'dt_needed', 'imported', 'exported', 'header'))
+
+
+def _get_os_name():
+  """Get the host OS name."""
+  if sys.platform == 'linux2':
+    return 'linux'
+  if sys.platform == 'darwin':
+    return 'darwin'
+  raise ValueError(sys.platform + ' is not supported')
+
+
+def _get_build_top():
+  """Find the build top of the source tree ($ANDROID_BUILD_TOP)."""
+  prev_path = None
+  curr_path = os.path.abspath(os.getcwd())
+  while prev_path != curr_path:
+    if os.path.exists(os.path.join(curr_path, '.repo')):
+      return curr_path
+    prev_path = curr_path
+    curr_path = os.path.dirname(curr_path)
+  return None
+
+
+def _select_latest_llvm_version(versions):
+  """Select the latest LLVM prebuilts version from a set of versions."""
+  pattern = re.compile('clang-r([0-9]+)([a-z]?)')
+  found_rev = 0
+  found_ver = None
+  for curr_ver in versions:
+    match = pattern.match(curr_ver)
+    if not match:
+      continue
+    curr_rev = int(match.group(1))
+    if not found_ver or curr_rev > found_rev or (
+        curr_rev == found_rev and curr_ver > found_ver):
+      found_rev = curr_rev
+      found_ver = curr_ver
+  return found_ver
+
+
+def _get_latest_llvm_version(llvm_dir):
+  """Find the latest LLVM prebuilts version from `llvm_dir`."""
+  return _select_latest_llvm_version(os.listdir(llvm_dir))
+
+
+def _get_llvm_dir():
+  """Find the path to LLVM prebuilts."""
+  build_top = _get_build_top()
+
+  llvm_prebuilts_base = os.environ.get('LLVM_PREBUILTS_BASE')
+  if not llvm_prebuilts_base:
+    llvm_prebuilts_base = os.path.join('prebuilts', 'clang', 'host')
+
+  llvm_dir = os.path.join(
+    build_top, llvm_prebuilts_base, _get_os_name() + '-x86')
+
+  if not os.path.exists(llvm_dir):
+    return None
+
+  llvm_prebuilts_version = os.environ.get('LLVM_PREBUILTS_VERSION')
+  if not llvm_prebuilts_version:
+    llvm_prebuilts_version = _get_latest_llvm_version(llvm_dir)
+
+  llvm_dir = os.path.join(llvm_dir, llvm_prebuilts_version)
+
+  if not os.path.exists(llvm_dir):
+    return None
+
+  return llvm_dir
+
+
+def _get_llvm_readobj():
+  """Find the path to llvm-readobj executable."""
+  llvm_dir = _get_llvm_dir()
+  llvm_readobj = os.path.join(llvm_dir, 'bin', 'llvm-readobj')
+  return llvm_readobj if os.path.exists(llvm_readobj) else 'llvm-readobj'
+
+
+class ELFError(ValueError):
+  """Generic ELF parse error"""
+  pass
+
+
+class ELFInvalidMagicError(ELFError):
+  """Invalid ELF magic word error"""
+  def __init__(self):
+    super(ELFInvalidMagicError, self).__init__('bad ELF magic')
+
+
+class ELFParser(object):
+  """ELF file parser"""
+
+  @classmethod
+  def _read_elf_header(cls, elf_file_path):
+    """Read the ELF magic word from the beginning of the file."""
+    with open(elf_file_path, 'rb') as elf_file:
+      buf = elf_file.read(struct.calcsize(_ELF_HEADER_STRUCT_FMT))
+      try:
+        return ELFHeader(*struct.unpack(_ELF_HEADER_STRUCT_FMT, buf))
+      except struct.error:
+        return None
+
+
+  @classmethod
+  def open(cls, elf_file_path, llvm_readobj):
+    """Open and parse the ELF file."""
+    # Parse the ELF header for simple sanity checks.
+    header = cls._read_elf_header(elf_file_path)
+    if not header or header.ei_magic != _ELF_MAGIC:
+      raise ELFInvalidMagicError()
+
+    # Run llvm-readobj and parse the output.
+    return cls._read_llvm_readobj(elf_file_path, header, llvm_readobj)
+
+
+  @classmethod
+  def _find_prefix(cls, pattern, lines_it):
+    """Iterate `lines_it` until finding a string that starts with `pattern`."""
+    for line in lines_it:
+      if line.startswith(pattern):
+        return True
+    return False
+
+
+  @classmethod
+  def _read_llvm_readobj(cls, elf_file_path, header, llvm_readobj):
+    """Run llvm-readobj and parse the output."""
+    proc = subprocess.Popen(
+      [llvm_readobj, '-dynamic-table', '-dyn-symbols', elf_file_path],
+      stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    out, _ = proc.communicate()
+    lines = out.splitlines()
+    return cls._parse_llvm_readobj(elf_file_path, header, lines)
+
+
+  @classmethod
+  def _parse_llvm_readobj(cls, elf_file_path, header, lines):
+    """Parse the output of llvm-readobj."""
+    lines_it = iter(lines)
+    imported, exported = cls._parse_dynamic_symbols(lines_it)
+    dt_soname, dt_needed = cls._parse_dynamic_table(elf_file_path, lines_it)
+    return ELF(dt_soname, dt_needed, imported, exported, header)
+
+
+  _DYNAMIC_SECTION_START_PATTERN = 'DynamicSection ['
+
+  _DYNAMIC_SECTION_NEEDED_PATTERN = re.compile(
+    '^  0x[0-9a-fA-F]+\\s+NEEDED\\s+Shared library: \\[(.*)\\]$')
+
+  _DYNAMIC_SECTION_SONAME_PATTERN = re.compile(
+    '^  0x[0-9a-fA-F]+\\s+SONAME\\s+Library soname: \\[(.*)\\]$')
+
+  _DYNAMIC_SECTION_END_PATTERN = ']'
+
+
+  @classmethod
+  def _parse_dynamic_table(cls, elf_file_path, lines_it):
+    """Parse the dynamic table section."""
+    dt_soname = os.path.basename(elf_file_path)
+    dt_needed = []
+
+    dynamic = cls._find_prefix(cls._DYNAMIC_SECTION_START_PATTERN, lines_it)
+    if not dynamic:
+      return (dt_soname, dt_needed)
+
+    for line in lines_it:
+      if line == cls._DYNAMIC_SECTION_END_PATTERN:
+        break
+
+      match = cls._DYNAMIC_SECTION_NEEDED_PATTERN.match(line)
+      if match:
+        dt_needed.append(match.group(1))
+        continue
+
+      match = cls._DYNAMIC_SECTION_SONAME_PATTERN.match(line)
+      if match:
+        dt_soname = match.group(1)
+        continue
+
+    return (dt_soname, dt_needed)
+
+
+  _DYNAMIC_SYMBOLS_START_PATTERN = 'DynamicSymbols ['
+  _DYNAMIC_SYMBOLS_END_PATTERN = ']'
+
+  _SYMBOL_ENTRY_START_PATTERN = '  Symbol {'
+  _SYMBOL_ENTRY_PATTERN = re.compile('^    ([A-Za-z0-9_]+): (.*)$')
+  _SYMBOL_ENTRY_PAREN_PATTERN = re.compile(
+    '\\s+\\((?:(?:\\d+)|(?:0x[0-9a-fA-F]+))\\)$')
+  _SYMBOL_ENTRY_END_PATTERN = '  }'
+
+
+  @classmethod
+  def _parse_symbol_name(cls, name_with_version):
+    """Split `name_with_version` into name and version. This function may split
+    at last occurrence of `@@` or `@`."""
+    name, version = name_with_version.rsplit('@', 1)
+    if name and name[-1] == '@':
+      name = name[:-1]
+    return (name, version)
+
+
+  @classmethod
+  def _parse_dynamic_symbols(cls, lines_it):
+    """Parse dynamic symbol table and collect imported and exported symbols."""
+    imported = collections.defaultdict(set)
+    exported = collections.defaultdict(set)
+
+    for symbol in cls._parse_dynamic_symbols_internal(lines_it):
+      name, version = cls._parse_symbol_name(symbol['Name'])
+      if name:
+        if symbol['Section'] == 'Undefined':
+          if symbol['Binding'] != 'Weak':
+            imported[name].add(version)
+        else:
+          if symbol['Binding'] != 'Local':
+            exported[name].add(version)
+
+    # Freeze the returned imported/exported dict.
+    return (dict(imported), dict(exported))
+
+
+  @classmethod
+  def _parse_dynamic_symbols_internal(cls, lines_it):
+    """Parse symbols entries and yield each symbols."""
+
+    if not cls._find_prefix(cls._DYNAMIC_SYMBOLS_START_PATTERN, lines_it):
+      return
+
+    for line in lines_it:
+      if line == cls._DYNAMIC_SYMBOLS_END_PATTERN:
+        return
+
+      if line == cls._SYMBOL_ENTRY_START_PATTERN:
+        symbol = {}
+        continue
+
+      if line == cls._SYMBOL_ENTRY_END_PATTERN:
+        yield symbol
+        symbol = None
+        continue
+
+      match = cls._SYMBOL_ENTRY_PATTERN.match(line)
+      if match:
+        key = match.group(1)
+        value = cls._SYMBOL_ENTRY_PAREN_PATTERN.sub('', match.group(2))
+        symbol[key] = value
+        continue
+
+
+class Checker(object):
+  """ELF file checker that checks DT_SONAME, DT_NEEDED, and symbols."""
+
+  def __init__(self, llvm_readobj):
+    self._file_path = ''
+    self._file_under_test = None
+    self._shared_libs = []
+
+    self._llvm_readobj = llvm_readobj
+
+
+  if sys.stderr.isatty():
+    _ERROR_TAG = '\033[0;1;31merror:\033[m'  # Red error
+    _NOTE_TAG = '\033[0;1;30mnote:\033[m'  # Black note
+  else:
+    _ERROR_TAG = 'error:'  # Red error
+    _NOTE_TAG = 'note:'  # Black note
+
+
+  def _error(self, *args):
+    """Emit an error to stderr."""
+    print(self._file_path + ': ' + self._ERROR_TAG, *args, file=sys.stderr)
+
+
+  def _note(self, *args):
+    """Emit a note to stderr."""
+    print(self._file_path + ': ' + self._NOTE_TAG, *args, file=sys.stderr)
+
+
+  def _load_elf_file(self, path, skip_bad_elf_magic):
+    """Load an ELF file from the `path`."""
+    try:
+      return ELFParser.open(path, self._llvm_readobj)
+    except (IOError, OSError):
+      self._error('Failed to open "{}".'.format(path))
+      sys.exit(2)
+    except ELFInvalidMagicError:
+      if skip_bad_elf_magic:
+        sys.exit(0)
+      else:
+        self._error('File "{}" must have a valid ELF magic word.'.format(path))
+        sys.exit(2)
+    except:
+      self._error('An unknown error occurred while opening "{}".'.format(path))
+      raise
+
+
+  def load_file_under_test(self, path, skip_bad_elf_magic,
+                           skip_unknown_elf_machine):
+    """Load file-under-test (either an executable or a shared lib)."""
+    self._file_path = path
+    self._file_under_test = self._load_elf_file(path, skip_bad_elf_magic)
+
+    if skip_unknown_elf_machine and \
+        self._file_under_test.header.e_machine not in _KNOWN_MACHINES:
+      sys.exit(0)
+
+
+  def load_shared_libs(self, shared_lib_paths):
+    """Load shared libraries."""
+    for path in shared_lib_paths:
+      self._shared_libs.append(self._load_elf_file(path, False))
+
+
+  def check_dt_soname(self, soname):
+    """Check whether DT_SONAME matches installation file name."""
+    if self._file_under_test.dt_soname != soname:
+      self._error('DT_SONAME "{}" must be equal to the file name "{}".'
+                  .format(self._file_under_test.dt_soname, soname))
+      sys.exit(2)
+
+
+  def check_dt_needed(self):
+    """Check whether all DT_NEEDED entries are specified in the build
+    system."""
+
+    missing_shared_libs = False
+
+    # Collect the DT_SONAMEs from shared libs specified in the build system.
+    specified_sonames = {lib.dt_soname for lib in self._shared_libs}
+
+    # Chech whether all DT_NEEDED entries are specified.
+    for lib in self._file_under_test.dt_needed:
+      if lib not in specified_sonames:
+        self._error('DT_NEEDED "{}" is not specified in shared_libs.'
+                    .format(lib.decode('utf-8')))
+        missing_shared_libs = True
+
+    if missing_shared_libs:
+      dt_needed = sorted(set(self._file_under_test.dt_needed))
+      modules = [re.sub('\\.so$', '', lib) for lib in dt_needed]
+
+      self._note()
+      self._note('Fix suggestions:')
+      self._note(
+        '  Android.bp: shared_libs: [' +
+        ', '.join('"' + module + '"' for module in modules) + '],')
+      self._note(
+        '  Android.mk: LOCAL_SHARED_LIBRARIES := ' + ' '.join(modules))
+
+      self._note()
+      self._note('If the fix above doesn\'t work, bypass this check with:')
+      self._note('  Android.bp: check_elf_files: false,')
+      self._note('  Android.mk: LOCAL_CHECK_ELF_FILES := false')
+
+      sys.exit(2)
+
+
+  @staticmethod
+  def _find_symbol(lib, name, version):
+    """Check whether the symbol name and version matches a definition in
+    lib."""
+    try:
+      lib_sym_vers = lib.exported[name]
+    except KeyError:
+      return False
+    if version == '':  # Symbol version is not requested
+      return True
+    return version in lib_sym_vers
+
+
+  @classmethod
+  def _find_symbol_from_libs(cls, libs, name, version):
+    """Check whether the symbol name and version is defined in one of the
+    shared libraries in libs."""
+    for lib in libs:
+      if cls._find_symbol(lib, name, version):
+        return lib
+    return None
+
+
+  def check_symbols(self):
+    """Check whether all undefined symbols are resolved to a definition."""
+    all_elf_files = [self._file_under_test] + self._shared_libs
+    missing_symbols = []
+    for sym, imported_vers in self._file_under_test.imported.iteritems():
+      for imported_ver in imported_vers:
+        lib = self._find_symbol_from_libs(all_elf_files, sym, imported_ver)
+        if not lib:
+          missing_symbols.append((sym, imported_ver))
+
+    if missing_symbols:
+      for sym, ver in sorted(missing_symbols):
+        sym = sym.decode('utf-8')
+        if ver:
+          sym += '@' + ver.decode('utf-8')
+        self._error('Unresolved symbol: {}'.format(sym))
+
+      self._note()
+      self._note('Some dependencies might be changed, thus the symbol(s) '
+                 'above cannot be resolved.')
+      self._note('Please re-build the prebuilt file: "{}".'
+                 .format(self._file_path))
+
+      self._note()
+      self._note('If this is a new prebuilt file and it is designed to have '
+                 'unresolved symbols, add one of the following properties:')
+      self._note('  Android.bp: allow_undefined_symbols: true,')
+      self._note('  Android.mk: LOCAL_ALLOW_UNDEFINED_SYMBOLS := true')
+
+      sys.exit(2)
+
+
+def _parse_args():
+  """Parse command line options."""
+  parser = argparse.ArgumentParser()
+
+  # Input file
+  parser.add_argument('file',
+                      help='Path to the input file to be checked')
+  parser.add_argument('--soname',
+                      help='Shared object name of the input file')
+
+  # Shared library dependencies
+  parser.add_argument('--shared-lib', action='append', default=[],
+                      help='Path to shared library dependencies')
+
+  # Check options
+  parser.add_argument('--skip-bad-elf-magic', action='store_true',
+                      help='Ignore the input file without the ELF magic word')
+  parser.add_argument('--skip-unknown-elf-machine', action='store_true',
+                      help='Ignore the input file with unknown machine ID')
+  parser.add_argument('--allow-undefined-symbols', action='store_true',
+                      help='Ignore unresolved undefined symbols')
+
+  # Other options
+  parser.add_argument('--llvm-readobj',
+                      help='Path to the llvm-readobj executable')
+
+  return parser.parse_args()
+
+
+def main():
+  """Main function"""
+  args = _parse_args()
+
+  llvm_readobj = args.llvm_readobj
+  if not llvm_readobj:
+    llvm_readobj = _get_llvm_readobj()
+
+  # Load ELF files
+  checker = Checker(llvm_readobj)
+  checker.load_file_under_test(
+    args.file, args.skip_bad_elf_magic, args.skip_unknown_elf_machine)
+  checker.load_shared_libs(args.shared_lib)
+
+  # Run checks
+  if args.soname:
+    checker.check_dt_soname(args.soname)
+
+  checker.check_dt_needed()
+
+  if not args.allow_undefined_symbols:
+    checker.check_symbols()
+
+
+if __name__ == '__main__':
+  main()