1 # Copyright 2016 Google Inc. All Rights Reserved. 2 # 3 # This script is used to help the compiler wrapper in the Android build system 4 # bisect for bad object files. 5 """Utilities for bisection of Android object files. 6 7 This module contains a set of utilities to allow bisection between 8 two sets (good and bad) of object files. Mostly used to find compiler 9 bugs. 10 11 Reference page: 12 https://sites.google.com/a/google.com/chromeos-toolchain-team-home2/home/team-tools-and-scripts/bisecting-chromeos-compiler-problems/bisection-compiler-wrapper 13 14 Design doc: 15 https://docs.google.com/document/d/1yDgaUIa2O5w6dc3sSTe1ry-1ehKajTGJGQCbyn0fcEM 16 """ 17 18 from __future__ import print_function 19 20 import contextlib 21 import fcntl 22 import os 23 import shutil 24 import subprocess 25 import sys 26 27 VALID_MODES = ['POPULATE_GOOD', 'POPULATE_BAD', 'TRIAGE'] 28 GOOD_CACHE = 'good' 29 BAD_CACHE = 'bad' 30 LIST_FILE = os.path.join(GOOD_CACHE, '_LIST') 31 32 CONTINUE_ON_MISSING = os.environ.get('BISECT_CONTINUE_ON_MISSING', None) == '1' 33 WRAPPER_SAFE_MODE = os.environ.get('BISECT_WRAPPER_SAFE_MODE', None) == '1' 34 35 36 class Error(Exception): 37 """The general compiler wrapper error class.""" 38 pass 39 40 41 @contextlib.contextmanager 42 def lock_file(path, mode): 43 """Lock file and block if other process has lock on file. 44 45 Acquire exclusive lock for file. Only blocks other processes if they attempt 46 to also acquire lock through this method. If only reading (modes 'r' and 'rb') 47 then the lock is shared (i.e. many reads can happen concurrently, but only one 48 process may write at a time). 49 50 This function is a contextmanager, meaning it's meant to be used with the 51 "with" statement in Python. This is so cleanup and setup happens automatically 52 and cleanly. Execution of the outer "with" statement happens at the "yield" 53 statement. Execution resumes after the yield when the outer "with" statement 54 ends. 55 56 Args: 57 path: path to file being locked 58 mode: mode to open file with ('w', 'r', etc.) 59 """ 60 with open(path, mode) as f: 61 # Share the lock if just reading, make lock exclusive if writing 62 if f.mode == 'r' or f.mode == 'rb': 63 lock_type = fcntl.LOCK_SH 64 else: 65 lock_type = fcntl.LOCK_EX 66 67 try: 68 fcntl.lockf(f, lock_type) 69 yield f 70 f.flush() 71 except: 72 raise 73 finally: 74 fcntl.lockf(f, fcntl.LOCK_UN) 75 76 77 def log_to_file(path, execargs, link_from=None, link_to=None): 78 """Common logging function. 79 80 Log current working directory, current execargs, and a from-to relationship 81 between files. 82 """ 83 with lock_file(path, 'a') as log: 84 log.write('cd: %s; %s\n' % (os.getcwd(), ' '.join(execargs))) 85 if link_from and link_to: 86 log.write('%s -> %s\n' % (link_from, link_to)) 87 88 89 def exec_and_return(execargs): 90 """Execute process and return. 91 92 Execute according to execargs and return immediately. Don't inspect 93 stderr or stdout. 94 """ 95 return subprocess.call(execargs) 96 97 98 def which_cache(obj_file): 99 """Determine which cache an object belongs to. 100 101 The binary search tool creates two files for each search iteration listing 102 the full set of bad objects and full set of good objects. We use this to 103 determine where an object file should be linked from (good or bad). 104 """ 105 bad_set_file = os.environ.get('BISECT_BAD_SET') 106 ret = subprocess.call(['grep', '-x', '-q', obj_file, bad_set_file]) 107 if ret == 0: 108 return BAD_CACHE 109 else: 110 return GOOD_CACHE 111 112 113 def makedirs(path): 114 """Try to create directories in path.""" 115 try: 116 os.makedirs(path) 117 except os.error: 118 if not os.path.isdir(path): 119 raise 120 121 122 def get_obj_path(execargs): 123 """Get the object path for the object file in the list of arguments. 124 125 Returns: 126 Absolute object path from execution args (-o argument). If no object being 127 outputted or output doesn't end in ".o" then return empty string. 128 """ 129 try: 130 i = execargs.index('-o') 131 except ValueError: 132 return '' 133 134 obj_path = execargs[i + 1] 135 if not obj_path.endswith(('.o',)): 136 # TODO: what suffixes do we need to contemplate 137 # TODO: add this as a warning 138 # TODO: need to handle -r compilations 139 return '' 140 141 return os.path.abspath(obj_path) 142 143 144 def get_dep_path(execargs): 145 """Get the dep file path for the dep file in the list of arguments. 146 147 Returns: 148 Absolute path of dependency file path from execution args (-o argument). If 149 no dependency being outputted then return empty string. 150 """ 151 if '-MD' not in execargs and '-MMD' not in execargs: 152 return '' 153 154 # If -MF given this is the path of the dependency file. Otherwise the 155 # dependency file is the value of -o but with a .d extension 156 if '-MF' in execargs: 157 i = execargs.index('-MF') 158 dep_path = execargs[i + 1] 159 return os.path.abspath(dep_path) 160 161 full_obj_path = get_obj_path(execargs) 162 if not full_obj_path: 163 return '' 164 165 return full_obj_path[:-2] + '.d' 166 167 168 def get_dwo_path(execargs): 169 """Get the dwo file path for the dwo file in the list of arguments. 170 171 Returns: 172 Absolute dwo file path from execution args (-gsplit-dwarf argument) If no 173 dwo file being outputted then return empty string. 174 """ 175 if '-gsplit-dwarf' not in execargs: 176 return '' 177 178 full_obj_path = get_obj_path(execargs) 179 if not full_obj_path: 180 return '' 181 182 return full_obj_path[:-2] + '.dwo' 183 184 185 def in_object_list(obj_name, list_filename): 186 """Check if object file name exist in file with object list.""" 187 if not obj_name: 188 return False 189 190 with lock_file(list_filename, 'r') as list_file: 191 for line in list_file: 192 if line.strip() == obj_name: 193 return True 194 195 return False 196 197 198 def get_side_effects(execargs): 199 """Determine side effects generated by compiler 200 201 Returns: 202 List of paths of objects that the compiler generates as side effects. 203 """ 204 side_effects = [] 205 206 # Cache dependency files 207 full_dep_path = get_dep_path(execargs) 208 if full_dep_path: 209 side_effects.append(full_dep_path) 210 211 # Cache dwo files 212 full_dwo_path = get_dwo_path(execargs) 213 if full_dwo_path: 214 side_effects.append(full_dwo_path) 215 216 return side_effects 217 218 219 def cache_file(execargs, bisect_dir, cache, abs_file_path): 220 """Cache compiler output file (.o/.d/.dwo).""" 221 # os.path.join fails with absolute paths, use + instead 222 bisect_path = os.path.join(bisect_dir, cache) + abs_file_path 223 bisect_path_dir = os.path.dirname(bisect_path) 224 makedirs(bisect_path_dir) 225 pop_log = os.path.join(bisect_dir, cache, '_POPULATE_LOG') 226 log_to_file(pop_log, execargs, abs_file_path, bisect_path) 227 228 try: 229 if os.path.exists(abs_file_path): 230 shutil.copy2(abs_file_path, bisect_path) 231 except Exception: 232 print('Could not cache file %s' % abs_file_path, file=sys.stderr) 233 raise 234 235 236 def restore_file(bisect_dir, cache, abs_file_path): 237 """Restore file from cache (.o/.d/.dwo).""" 238 # os.path.join fails with absolute paths, use + instead 239 cached_path = os.path.join(bisect_dir, cache) + abs_file_path 240 if os.path.exists(cached_path): 241 if os.path.exists(abs_file_path): 242 os.remove(abs_file_path) 243 os.link(cached_path, abs_file_path) 244 else: 245 raise Error(('%s is missing from %s cache! Unsure how to proceed. Make ' 246 'will now crash.' % (cache, cached_path))) 247 248 249 def bisect_populate(execargs, bisect_dir, population_name): 250 """Add necessary information to the bisect cache for the given execution. 251 252 Extract the necessary information for bisection from the compiler 253 execution arguments and put it into the bisection cache. This 254 includes copying the created object file, adding the object 255 file path to the cache list and keeping a log of the execution. 256 257 Args: 258 execargs: compiler execution arguments. 259 bisect_dir: bisection directory. 260 population_name: name of the cache being populated (good/bad). 261 """ 262 retval = exec_and_return(execargs) 263 if retval: 264 return retval 265 266 full_obj_path = get_obj_path(execargs) 267 # If not a normal compiler call then just exit 268 if not full_obj_path: 269 return 270 271 cache_file(execargs, bisect_dir, population_name, full_obj_path) 272 273 population_dir = os.path.join(bisect_dir, population_name) 274 with lock_file(os.path.join(population_dir, '_LIST'), 'a') as object_list: 275 object_list.write('%s\n' % full_obj_path) 276 277 for side_effect in get_side_effects(execargs): 278 cache_file(execargs, bisect_dir, population_name, side_effect) 279 280 281 def bisect_triage(execargs, bisect_dir): 282 full_obj_path = get_obj_path(execargs) 283 obj_list = os.path.join(bisect_dir, LIST_FILE) 284 285 # If the output isn't an object file just call compiler 286 if not full_obj_path: 287 return exec_and_return(execargs) 288 289 # If this isn't a bisected object just call compiler 290 # This shouldn't happen! 291 if not in_object_list(full_obj_path, obj_list): 292 if CONTINUE_ON_MISSING: 293 log_file = os.path.join(bisect_dir, '_MISSING_CACHED_OBJ_LOG') 294 log_to_file(log_file, execargs, '? compiler', full_obj_path) 295 return exec_and_return(execargs) 296 else: 297 raise Error(('%s is missing from cache! To ignore export ' 298 'BISECT_CONTINUE_ON_MISSING=1. See documentation for more ' 299 'details on this option.' % full_obj_path)) 300 301 cache = which_cache(full_obj_path) 302 303 # If using safe WRAPPER_SAFE_MODE option call compiler and overwrite the 304 # result from the good/bad cache. This option is safe and covers all compiler 305 # side effects, but is very slow! 306 if WRAPPER_SAFE_MODE: 307 retval = exec_and_return(execargs) 308 if retval: 309 return retval 310 os.remove(full_obj_path) 311 restore_file(bisect_dir, cache, full_obj_path) 312 return 313 314 # Generate compiler side effects. Trick Make into thinking compiler was 315 # actually executed. 316 for side_effect in get_side_effects(execargs): 317 restore_file(bisect_dir, cache, side_effect) 318 319 # If generated object file happened to be pruned/cleaned by Make then link it 320 # over from cache again. 321 if not os.path.exists(full_obj_path): 322 restore_file(bisect_dir, cache, full_obj_path) 323 324 325 def bisect_driver(bisect_stage, bisect_dir, execargs): 326 """Call appropriate bisection stage according to value in bisect_stage.""" 327 if bisect_stage == 'POPULATE_GOOD': 328 bisect_populate(execargs, bisect_dir, GOOD_CACHE) 329 elif bisect_stage == 'POPULATE_BAD': 330 bisect_populate(execargs, bisect_dir, BAD_CACHE) 331 elif bisect_stage == 'TRIAGE': 332 bisect_triage(execargs, bisect_dir) 333 else: 334 raise ValueError('wrong value for BISECT_STAGE: %s' % bisect_stage) 335
