| # Copyright 2014 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. |
| |
| import collections |
| import datetime |
| import logging |
| import multiprocessing |
| import os |
| import posixpath |
| import Queue |
| import re |
| import subprocess |
| import sys |
| import threading |
| import time |
| |
| |
| # addr2line builds a possibly infinite memory cache that can exhaust |
| # the computer's memory if allowed to grow for too long. This constant |
| # controls how many lookups we do before restarting the process. 4000 |
| # gives near peak performance without extreme memory usage. |
| ADDR2LINE_RECYCLE_LIMIT = 4000 |
| |
| |
| class ELFSymbolizer(object): |
| """An uber-fast (multiprocessing, pipelined and asynchronous) ELF symbolizer. |
| |
| This class is a frontend for addr2line (part of GNU binutils), designed to |
| symbolize batches of large numbers of symbols for a given ELF file. It |
| supports sharding symbolization against many addr2line instances and |
| pipelining of multiple requests per each instance (in order to hide addr2line |
| internals and OS pipe latencies). |
| |
| The interface exhibited by this class is a very simple asynchronous interface, |
| which is based on the following three methods: |
| - SymbolizeAsync(): used to request (enqueue) resolution of a given address. |
| - The |callback| method: used to communicated back the symbol information. |
| - Join(): called to conclude the batch to gather the last outstanding results. |
| In essence, before the Join method returns, this class will have issued as |
| many callbacks as the number of SymbolizeAsync() calls. In this regard, note |
| that due to multiprocess sharding, callbacks can be delivered out of order. |
| |
| Some background about addr2line: |
| - it is invoked passing the elf path in the cmdline, piping the addresses in |
| its stdin and getting results on its stdout. |
| - it has pretty large response times for the first requests, but it |
| works very well in streaming mode once it has been warmed up. |
| - it doesn't scale by itself (on more cores). However, spawning multiple |
| instances at the same time on the same file is pretty efficient as they |
| keep hitting the pagecache and become mostly CPU bound. |
| - it might hang or crash, mostly for OOM. This class deals with both of these |
| problems. |
| |
| Despite the "scary" imports and the multi* words above, (almost) no multi- |
| threading/processing is involved from the python viewpoint. Concurrency |
| here is achieved by spawning several addr2line subprocesses and handling their |
| output pipes asynchronously. Therefore, all the code here (with the exception |
| of the Queue instance in Addr2Line) should be free from mind-blowing |
| thread-safety concerns. |
| |
| The multiprocess sharding works as follows: |
| The symbolizer tries to use the lowest number of addr2line instances as |
| possible (with respect of |max_concurrent_jobs|) and enqueue all the requests |
| in a single addr2line instance. For few symbols (i.e. dozens) sharding isn't |
| worth the startup cost. |
| The multiprocess logic kicks in as soon as the queues for the existing |
| instances grow. Specifically, once all the existing instances reach the |
| |max_queue_size| bound, a new addr2line instance is kicked in. |
| In the case of a very eager producer (i.e. all |max_concurrent_jobs| instances |
| have a backlog of |max_queue_size|), back-pressure is applied on the caller by |
| blocking the SymbolizeAsync method. |
| |
| This module has been deliberately designed to be dependency free (w.r.t. of |
| other modules in this project), to allow easy reuse in external projects. |
| """ |
| |
| def __init__(self, elf_file_path, addr2line_path, callback, inlines=False, |
| max_concurrent_jobs=None, addr2line_timeout=30, max_queue_size=50, |
| source_root_path=None, strip_base_path=None): |
| """Args: |
| elf_file_path: path of the elf file to be symbolized. |
| addr2line_path: path of the toolchain's addr2line binary. |
| callback: a callback which will be invoked for each resolved symbol with |
| the two args (sym_info, callback_arg). The former is an instance of |
| |ELFSymbolInfo| and contains the symbol information. The latter is an |
| embedder-provided argument which is passed to SymbolizeAsync(). |
| inlines: when True, the ELFSymbolInfo will contain also the details about |
| the outer inlining functions. When False, only the innermost function |
| will be provided. |
| max_concurrent_jobs: Max number of addr2line instances spawned. |
| Parallelize responsibly, addr2line is a memory and I/O monster. |
| max_queue_size: Max number of outstanding requests per addr2line instance. |
| addr2line_timeout: Max time (in seconds) to wait for a addr2line response. |
| After the timeout, the instance will be considered hung and respawned. |
| source_root_path: In some toolchains only the name of the source file is |
| is output, without any path information; disambiguation searches |
| through the source directory specified by |source_root_path| argument |
| for files whose name matches, adding the full path information to the |
| output. For example, if the toolchain outputs "unicode.cc" and there |
| is a file called "unicode.cc" located under |source_root_path|/foo, |
| the tool will replace "unicode.cc" with |
| "|source_root_path|/foo/unicode.cc". If there are multiple files with |
| the same name, disambiguation will fail because the tool cannot |
| determine which of the files was the source of the symbol. |
| strip_base_path: Rebases the symbols source paths onto |source_root_path| |
| (i.e replace |strip_base_path| with |source_root_path). |
| """ |
| assert(os.path.isfile(addr2line_path)), 'Cannot find ' + addr2line_path |
| self.elf_file_path = elf_file_path |
| self.addr2line_path = addr2line_path |
| self.callback = callback |
| self.inlines = inlines |
| self.max_concurrent_jobs = (max_concurrent_jobs or |
| min(multiprocessing.cpu_count(), 4)) |
| self.max_queue_size = max_queue_size |
| self.addr2line_timeout = addr2line_timeout |
| self.requests_counter = 0 # For generating monotonic request IDs. |
| self._a2l_instances = [] # Up to |max_concurrent_jobs| _Addr2Line inst. |
| |
| # If necessary, create disambiguation lookup table |
| self.disambiguate = source_root_path is not None |
| self.disambiguation_table = {} |
| self.strip_base_path = strip_base_path |
| if(self.disambiguate): |
| self.source_root_path = os.path.abspath(source_root_path) |
| self._CreateDisambiguationTable() |
| |
| # Create one addr2line instance. More instances will be created on demand |
| # (up to |max_concurrent_jobs|) depending on the rate of the requests. |
| self._CreateNewA2LInstance() |
| |
| def SymbolizeAsync(self, addr, callback_arg=None): |
| """Requests symbolization of a given address. |
| |
| This method is not guaranteed to return immediately. It generally does, but |
| in some scenarios (e.g. all addr2line instances have full queues) it can |
| block to create back-pressure. |
| |
| Args: |
| addr: address to symbolize. |
| callback_arg: optional argument which will be passed to the |callback|.""" |
| assert(isinstance(addr, int)) |
| |
| # Process all the symbols that have been resolved in the meanwhile. |
| # Essentially, this drains all the addr2line(s) out queues. |
| for a2l_to_purge in self._a2l_instances: |
| a2l_to_purge.ProcessAllResolvedSymbolsInQueue() |
| a2l_to_purge.RecycleIfNecessary() |
| |
| # Find the best instance according to this logic: |
| # 1. Find an existing instance with the shortest queue. |
| # 2. If all of instances' queues are full, but there is room in the pool, |
| # (i.e. < |max_concurrent_jobs|) create a new instance. |
| # 3. If there were already |max_concurrent_jobs| instances and all of them |
| # had full queues, make back-pressure. |
| |
| # 1. |
| def _SortByQueueSizeAndReqID(a2l): |
| return (a2l.queue_size, a2l.first_request_id) |
| a2l = min(self._a2l_instances, key=_SortByQueueSizeAndReqID) |
| |
| # 2. |
| if (a2l.queue_size >= self.max_queue_size and |
| len(self._a2l_instances) < self.max_concurrent_jobs): |
| a2l = self._CreateNewA2LInstance() |
| |
| # 3. |
| if a2l.queue_size >= self.max_queue_size: |
| a2l.WaitForNextSymbolInQueue() |
| |
| a2l.EnqueueRequest(addr, callback_arg) |
| |
| def Join(self): |
| """Waits for all the outstanding requests to complete and terminates.""" |
| for a2l in self._a2l_instances: |
| a2l.WaitForIdle() |
| a2l.Terminate() |
| |
| def _CreateNewA2LInstance(self): |
| assert(len(self._a2l_instances) < self.max_concurrent_jobs) |
| a2l = ELFSymbolizer.Addr2Line(self) |
| self._a2l_instances.append(a2l) |
| return a2l |
| |
| def _CreateDisambiguationTable(self): |
| """ Non-unique file names will result in None entries""" |
| start_time = time.time() |
| logging.info('Collecting information about available source files...') |
| self.disambiguation_table = {} |
| |
| for root, _, filenames in os.walk(self.source_root_path): |
| for f in filenames: |
| self.disambiguation_table[f] = os.path.join(root, f) if (f not in |
| self.disambiguation_table) else None |
| logging.info('Finished collecting information about ' |
| 'possible files (took %.1f s).', |
| (time.time() - start_time)) |
| |
| |
| class Addr2Line(object): |
| """A python wrapper around an addr2line instance. |
| |
| The communication with the addr2line process looks as follows: |
| [STDIN] [STDOUT] (from addr2line's viewpoint) |
| > f001111 |
| > f002222 |
| < Symbol::Name(foo, bar) for f001111 |
| < /path/to/source/file.c:line_number |
| > f003333 |
| < Symbol::Name2() for f002222 |
| < /path/to/source/file.c:line_number |
| < Symbol::Name3() for f003333 |
| < /path/to/source/file.c:line_number |
| """ |
| |
| SYM_ADDR_RE = re.compile(r'([^:]+):(\?|\d+).*') |
| |
| def __init__(self, symbolizer): |
| self._symbolizer = symbolizer |
| self._lib_file_name = posixpath.basename(symbolizer.elf_file_path) |
| |
| # The request queue (i.e. addresses pushed to addr2line's stdin and not |
| # yet retrieved on stdout) |
| self._request_queue = collections.deque() |
| |
| # This is essentially len(self._request_queue). It has been optimized to a |
| # separate field because turned out to be a perf hot-spot. |
| self.queue_size = 0 |
| |
| # Keep track of the number of symbols a process has processed to |
| # avoid a single process growing too big and using all the memory. |
| self._processed_symbols_count = 0 |
| |
| # Objects required to handle the addr2line subprocess. |
| self._proc = None # Subprocess.Popen(...) instance. |
| self._thread = None # Threading.thread instance. |
| self._out_queue = None # Queue.Queue instance (for buffering a2l stdout). |
| self._RestartAddr2LineProcess() |
| |
| def EnqueueRequest(self, addr, callback_arg): |
| """Pushes an address to addr2line's stdin (and keeps track of it).""" |
| self._symbolizer.requests_counter += 1 # For global "age" of requests. |
| req_idx = self._symbolizer.requests_counter |
| self._request_queue.append((addr, callback_arg, req_idx)) |
| self.queue_size += 1 |
| self._WriteToA2lStdin(addr) |
| |
| def WaitForIdle(self): |
| """Waits until all the pending requests have been symbolized.""" |
| while self.queue_size > 0: |
| self.WaitForNextSymbolInQueue() |
| |
| def WaitForNextSymbolInQueue(self): |
| """Waits for the next pending request to be symbolized.""" |
| if not self.queue_size: |
| return |
| |
| # This outer loop guards against a2l hanging (detecting stdout timeout). |
| while True: |
| start_time = datetime.datetime.now() |
| timeout = datetime.timedelta(seconds=self._symbolizer.addr2line_timeout) |
| |
| # The inner loop guards against a2l crashing (checking if it exited). |
| while (datetime.datetime.now() - start_time < timeout): |
| # poll() returns !None if the process exited. a2l should never exit. |
| if self._proc.poll(): |
| logging.warning('addr2line crashed, respawning (lib: %s).' % |
| self._lib_file_name) |
| self._RestartAddr2LineProcess() |
| # TODO(primiano): the best thing to do in this case would be |
| # shrinking the pool size as, very likely, addr2line is crashed |
| # due to low memory (and the respawned one will die again soon). |
| |
| try: |
| lines = self._out_queue.get(block=True, timeout=0.25) |
| except Queue.Empty: |
| # On timeout (1/4 s.) repeat the inner loop and check if either the |
| # addr2line process did crash or we waited its output for too long. |
| continue |
| |
| # In nominal conditions, we get straight to this point. |
| self._ProcessSymbolOutput(lines) |
| return |
| |
| # If this point is reached, we waited more than |addr2line_timeout|. |
| logging.warning('Hung addr2line process, respawning (lib: %s).' % |
| self._lib_file_name) |
| self._RestartAddr2LineProcess() |
| |
| def ProcessAllResolvedSymbolsInQueue(self): |
| """Consumes all the addr2line output lines produced (without blocking).""" |
| if not self.queue_size: |
| return |
| while True: |
| try: |
| lines = self._out_queue.get_nowait() |
| except Queue.Empty: |
| break |
| self._ProcessSymbolOutput(lines) |
| |
| def RecycleIfNecessary(self): |
| """Restarts the process if it has been used for too long. |
| |
| A long running addr2line process will consume excessive amounts |
| of memory without any gain in performance.""" |
| if self._processed_symbols_count >= ADDR2LINE_RECYCLE_LIMIT: |
| self._RestartAddr2LineProcess() |
| |
| |
| def Terminate(self): |
| """Kills the underlying addr2line process. |
| |
| The poller |_thread| will terminate as well due to the broken pipe.""" |
| try: |
| self._proc.kill() |
| self._proc.communicate() # Essentially wait() without risking deadlock. |
| except Exception: # An exception while terminating? How interesting. |
| pass |
| self._proc = None |
| |
| def _WriteToA2lStdin(self, addr): |
| self._proc.stdin.write('%s\n' % hex(addr)) |
| if self._symbolizer.inlines: |
| # In the case of inlines we output an extra blank line, which causes |
| # addr2line to emit a (??,??:0) tuple that we use as a boundary marker. |
| self._proc.stdin.write('\n') |
| self._proc.stdin.flush() |
| |
| def _ProcessSymbolOutput(self, lines): |
| """Parses an addr2line symbol output and triggers the client callback.""" |
| (_, callback_arg, _) = self._request_queue.popleft() |
| self.queue_size -= 1 |
| |
| innermost_sym_info = None |
| sym_info = None |
| for (line1, line2) in lines: |
| prev_sym_info = sym_info |
| name = line1 if not line1.startswith('?') else None |
| source_path = None |
| source_line = None |
| m = ELFSymbolizer.Addr2Line.SYM_ADDR_RE.match(line2) |
| if m: |
| if not m.group(1).startswith('?'): |
| source_path = m.group(1) |
| if not m.group(2).startswith('?'): |
| source_line = int(m.group(2)) |
| else: |
| logging.warning('Got invalid symbol path from addr2line: %s' % line2) |
| |
| # In case disambiguation is on, and needed |
| was_ambiguous = False |
| disambiguated = False |
| if self._symbolizer.disambiguate: |
| if source_path and not posixpath.isabs(source_path): |
| path = self._symbolizer.disambiguation_table.get(source_path) |
| was_ambiguous = True |
| disambiguated = path is not None |
| source_path = path if disambiguated else source_path |
| |
| # Use absolute paths (so that paths are consistent, as disambiguation |
| # uses absolute paths) |
| if source_path and not was_ambiguous: |
| source_path = os.path.abspath(source_path) |
| |
| if source_path and self._symbolizer.strip_base_path: |
| # Strip the base path |
| source_path = re.sub('^' + self._symbolizer.strip_base_path, |
| self._symbolizer.source_root_path or '', source_path) |
| |
| sym_info = ELFSymbolInfo(name, source_path, source_line, was_ambiguous, |
| disambiguated) |
| if prev_sym_info: |
| prev_sym_info.inlined_by = sym_info |
| if not innermost_sym_info: |
| innermost_sym_info = sym_info |
| |
| self._processed_symbols_count += 1 |
| self._symbolizer.callback(innermost_sym_info, callback_arg) |
| |
| def _RestartAddr2LineProcess(self): |
| if self._proc: |
| self.Terminate() |
| |
| # The only reason of existence of this Queue (and the corresponding |
| # Thread below) is the lack of a subprocess.stdout.poll_avail_lines(). |
| # Essentially this is a pipe able to extract a couple of lines atomically. |
| self._out_queue = Queue.Queue() |
| |
| # Start the underlying addr2line process in line buffered mode. |
| |
| cmd = [self._symbolizer.addr2line_path, '--functions', '--demangle', |
| '--exe=' + self._symbolizer.elf_file_path] |
| if self._symbolizer.inlines: |
| cmd += ['--inlines'] |
| self._proc = subprocess.Popen(cmd, bufsize=1, stdout=subprocess.PIPE, |
| stdin=subprocess.PIPE, stderr=sys.stderr, close_fds=True) |
| |
| # Start the poller thread, which simply moves atomically the lines read |
| # from the addr2line's stdout to the |_out_queue|. |
| self._thread = threading.Thread( |
| target=ELFSymbolizer.Addr2Line.StdoutReaderThread, |
| args=(self._proc.stdout, self._out_queue, self._symbolizer.inlines)) |
| self._thread.daemon = True # Don't prevent early process exit. |
| self._thread.start() |
| |
| self._processed_symbols_count = 0 |
| |
| # Replay the pending requests on the new process (only for the case |
| # of a hung addr2line timing out during the game). |
| for (addr, _, _) in self._request_queue: |
| self._WriteToA2lStdin(addr) |
| |
| @staticmethod |
| def StdoutReaderThread(process_pipe, queue, inlines): |
| """The poller thread fn, which moves the addr2line stdout to the |queue|. |
| |
| This is the only piece of code not running on the main thread. It merely |
| writes to a Queue, which is thread-safe. In the case of inlines, it |
| detects the ??,??:0 marker and sends the lines atomically, such that the |
| main thread always receives all the lines corresponding to one symbol in |
| one shot.""" |
| try: |
| lines_for_one_symbol = [] |
| while True: |
| line1 = process_pipe.readline().rstrip('\r\n') |
| line2 = process_pipe.readline().rstrip('\r\n') |
| if not line1 or not line2: |
| break |
| inline_has_more_lines = inlines and (len(lines_for_one_symbol) == 0 or |
| (line1 != '??' and line2 != '??:0')) |
| if not inlines or inline_has_more_lines: |
| lines_for_one_symbol += [(line1, line2)] |
| if inline_has_more_lines: |
| continue |
| queue.put(lines_for_one_symbol) |
| lines_for_one_symbol = [] |
| process_pipe.close() |
| |
| # Every addr2line processes will die at some point, please die silently. |
| except (IOError, OSError): |
| pass |
| |
| @property |
| def first_request_id(self): |
| """Returns the request_id of the oldest pending request in the queue.""" |
| return self._request_queue[0][2] if self._request_queue else 0 |
| |
| |
| class ELFSymbolInfo(object): |
| """The result of the symbolization passed as first arg. of each callback.""" |
| |
| def __init__(self, name, source_path, source_line, was_ambiguous=False, |
| disambiguated=False): |
| """All the fields here can be None (if addr2line replies with '??').""" |
| self.name = name |
| self.source_path = source_path |
| self.source_line = source_line |
| # In the case of |inlines|=True, the |inlined_by| points to the outer |
| # function inlining the current one (and so on, to form a chain). |
| self.inlined_by = None |
| self.disambiguated = disambiguated |
| self.was_ambiguous = was_ambiguous |
| |
| def __str__(self): |
| return '%s [%s:%d]' % ( |
| self.name or '??', self.source_path or '??', self.source_line or 0) |
