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# Copyright 2017 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
import functools
import logging
import os
import subprocess
import threading
_CHROME_SRC = os.path.join(os.path.dirname(__file__), os.pardir, os.pardir)
_LLVM_SYMBOLIZER_PATH = os.path.join(
_CHROME_SRC, 'third_party', 'llvm-build', 'Release+Asserts', 'bin',
'llvm-symbolizer')
_UNKNOWN = '<UNKNOWN>'
_ELF_MAGIC_HEADER_BYTES = b'\x7f\x45\x4c\x46'
@functools.lru_cache
def IsValidLLVMSymbolizerTarget(file_path):
""" Verify the passed file is a valid target for llvm-symbolization
Args:
file_path: Path to a file to be checked
Return:
True if the file exists and has the correct ELF header, False otherwise
"""
try:
with open(file_path, 'rb') as f:
header_bytes = f.read(4)
return header_bytes == _ELF_MAGIC_HEADER_BYTES
except IOError:
return False
class LLVMSymbolizer(object):
def __init__(self):
"""Create a LLVMSymbolizer instance that interacts with the llvm symbolizer.
The purpose of the LLVMSymbolizer is to get function names and line
numbers of an address from the symbols library.
"""
self._llvm_symbolizer_subprocess = None
self._llvm_symbolizer_parameters = [
'--functions',
'--demangle',
'--inlines',
]
# Allow only one thread to call GetSymbolInformation at a time.
self._lock = threading.Lock()
def Start(self):
"""Start the llvm symbolizer subprocess.
Create a subprocess of the llvm symbolizer executable, which will be used
to retrieve function names etc.
"""
if os.path.isfile(_LLVM_SYMBOLIZER_PATH):
self._llvm_symbolizer_subprocess = subprocess.Popen(
[_LLVM_SYMBOLIZER_PATH] + self._llvm_symbolizer_parameters,
stdout=subprocess.PIPE,
stdin=subprocess.PIPE,
universal_newlines=True)
else:
logging.error('Cannot find llvm_symbolizer here: %s.' %
_LLVM_SYMBOLIZER_PATH)
self._llvm_symbolizer_subprocess = None
def Close(self):
"""Close the llvm symbolizer subprocess.
Close the subprocess by closing stdin, stdout and killing the subprocess.
"""
with self._lock:
if self._llvm_symbolizer_subprocess:
self._llvm_symbolizer_subprocess.kill()
self._llvm_symbolizer_subprocess = None
def __enter__(self):
"""Start the llvm symbolizer subprocess."""
self.Start()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
"""Close the llvm symbolizer subprocess."""
self.Close()
def GetSymbolInformation(self, lib, addr):
"""Return the corresponding function names and line numbers.
Args:
lib: library to search for info.
addr: address to look for info.
Returns:
A triplet of address, module-name and list of symbols
"""
if (self._llvm_symbolizer_subprocess is None):
logging.error('Can\'t run llvm-symbolizer! ' +
'Subprocess for llvm-symbolizer has not been started!')
return [(_UNKNOWN, lib)]
if not lib:
logging.error('Can\'t run llvm-symbolizer! No target is given!')
return [(_UNKNOWN, lib)]
if not IsValidLLVMSymbolizerTarget(lib):
logging.error(
'Can\'t run llvm-symbolizer! ' +
'Given binary is not a valid target. path=%s', lib)
return [(_UNKNOWN, lib)]
proc = self._llvm_symbolizer_subprocess
with self._lock:
proc.stdin.write('%s %s\n' % (lib, hex(addr)))
proc.stdin.flush()
result = []
# Read until an empty line is observed, which indicates the end of the
# output. Each line with a function name is always followed by one line
# with the corresponding line number.
while True:
line = proc.stdout.readline()
if line != '\n':
line_numbers = proc.stdout.readline()
result.append((line[:-1], line_numbers[:-1]))
else:
return result
@staticmethod
def IsValidTarget(path):
return IsValidLLVMSymbolizerTarget(path)
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