ZygoteInit.java revision 89d4c897a0e1bc06688bcb1fd39913ece81fe05f
1/* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.android.internal.os; 18 19import static libcore.io.OsConstants.S_IRWXG; 20import static libcore.io.OsConstants.S_IRWXO; 21 22import android.content.res.Resources; 23import android.content.res.TypedArray; 24import android.net.LocalServerSocket; 25import android.opengl.EGL14; 26import android.os.Debug; 27import android.os.Process; 28import android.os.SystemClock; 29import android.os.SystemProperties; 30import android.os.Trace; 31import android.util.EventLog; 32import android.util.Log; 33 34import dalvik.system.VMRuntime; 35import dalvik.system.Zygote; 36 37import libcore.io.IoUtils; 38import libcore.io.Libcore; 39import libcore.io.OsConstants; 40 41import java.io.BufferedReader; 42import java.io.FileDescriptor; 43import java.io.IOException; 44import java.io.InputStream; 45import java.io.InputStreamReader; 46import java.lang.reflect.InvocationTargetException; 47import java.lang.reflect.Method; 48import java.lang.reflect.Modifier; 49import java.util.ArrayList; 50 51/** 52 * Startup class for the zygote process. 53 * 54 * Pre-initializes some classes, and then waits for commands on a UNIX domain 55 * socket. Based on these commands, forks off child processes that inherit 56 * the initial state of the VM. 57 * 58 * Please see {@link ZygoteConnection.Arguments} for documentation on the 59 * client protocol. 60 * 61 * @hide 62 */ 63public class ZygoteInit { 64 private static final String TAG = "Zygote"; 65 66 private static final String PROPERTY_DISABLE_OPENGL_PRELOADING = "ro.zygote.disable_gl_preload"; 67 68 private static final String ANDROID_SOCKET_ENV = "ANDROID_SOCKET_zygote"; 69 70 private static final int LOG_BOOT_PROGRESS_PRELOAD_START = 3020; 71 private static final int LOG_BOOT_PROGRESS_PRELOAD_END = 3030; 72 73 /** when preloading, GC after allocating this many bytes */ 74 private static final int PRELOAD_GC_THRESHOLD = 50000; 75 76 public static final String USAGE_STRING = 77 " <\"start-system-server\"|\"\" for startSystemServer>"; 78 79 private static LocalServerSocket sServerSocket; 80 81 /** 82 * Used to pre-load resources. We hold a global reference on it so it 83 * never gets destroyed. 84 */ 85 private static Resources mResources; 86 87 /** 88 * The number of times that the main Zygote loop 89 * should run before calling gc() again. 90 */ 91 static final int GC_LOOP_COUNT = 10; 92 93 /** 94 * The name of a resource file that contains classes to preload. 95 */ 96 private static final String PRELOADED_CLASSES = "preloaded-classes"; 97 98 /** Controls whether we should preload resources during zygote init. */ 99 private static final boolean PRELOAD_RESOURCES = true; 100 101 /** 102 * Invokes a static "main(argv[]) method on class "className". 103 * Converts various failing exceptions into RuntimeExceptions, with 104 * the assumption that they will then cause the VM instance to exit. 105 * 106 * @param loader class loader to use 107 * @param className Fully-qualified class name 108 * @param argv Argument vector for main() 109 */ 110 static void invokeStaticMain(ClassLoader loader, 111 String className, String[] argv) 112 throws ZygoteInit.MethodAndArgsCaller { 113 Class<?> cl; 114 115 try { 116 cl = loader.loadClass(className); 117 } catch (ClassNotFoundException ex) { 118 throw new RuntimeException( 119 "Missing class when invoking static main " + className, 120 ex); 121 } 122 123 Method m; 124 try { 125 m = cl.getMethod("main", new Class[] { String[].class }); 126 } catch (NoSuchMethodException ex) { 127 throw new RuntimeException( 128 "Missing static main on " + className, ex); 129 } catch (SecurityException ex) { 130 throw new RuntimeException( 131 "Problem getting static main on " + className, ex); 132 } 133 134 int modifiers = m.getModifiers(); 135 if (! (Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers))) { 136 throw new RuntimeException( 137 "Main method is not public and static on " + className); 138 } 139 140 /* 141 * This throw gets caught in ZygoteInit.main(), which responds 142 * by invoking the exception's run() method. This arrangement 143 * clears up all the stack frames that were required in setting 144 * up the process. 145 */ 146 throw new ZygoteInit.MethodAndArgsCaller(m, argv); 147 } 148 149 /** 150 * Registers a server socket for zygote command connections 151 * 152 * @throws RuntimeException when open fails 153 */ 154 private static void registerZygoteSocket() { 155 if (sServerSocket == null) { 156 int fileDesc; 157 try { 158 String env = System.getenv(ANDROID_SOCKET_ENV); 159 fileDesc = Integer.parseInt(env); 160 } catch (RuntimeException ex) { 161 throw new RuntimeException( 162 ANDROID_SOCKET_ENV + " unset or invalid", ex); 163 } 164 165 try { 166 sServerSocket = new LocalServerSocket( 167 createFileDescriptor(fileDesc)); 168 } catch (IOException ex) { 169 throw new RuntimeException( 170 "Error binding to local socket '" + fileDesc + "'", ex); 171 } 172 } 173 } 174 175 /** 176 * Waits for and accepts a single command connection. Throws 177 * RuntimeException on failure. 178 */ 179 private static ZygoteConnection acceptCommandPeer() { 180 try { 181 return new ZygoteConnection(sServerSocket.accept()); 182 } catch (IOException ex) { 183 throw new RuntimeException( 184 "IOException during accept()", ex); 185 } 186 } 187 188 /** 189 * Close and clean up zygote sockets. Called on shutdown and on the 190 * child's exit path. 191 */ 192 static void closeServerSocket() { 193 try { 194 if (sServerSocket != null) { 195 sServerSocket.close(); 196 } 197 } catch (IOException ex) { 198 Log.e(TAG, "Zygote: error closing sockets", ex); 199 } 200 201 sServerSocket = null; 202 } 203 204 /** 205 * Return the server socket's underlying file descriptor, so that 206 * ZygoteConnection can pass it to the native code for proper 207 * closure after a child process is forked off. 208 */ 209 210 static FileDescriptor getServerSocketFileDescriptor() { 211 return sServerSocket.getFileDescriptor(); 212 } 213 214 private static final int UNPRIVILEGED_UID = 9999; 215 private static final int UNPRIVILEGED_GID = 9999; 216 217 private static final int ROOT_UID = 0; 218 private static final int ROOT_GID = 0; 219 220 /** 221 * Sets effective user ID. 222 */ 223 private static void setEffectiveUser(int uid) { 224 int errno = setreuid(ROOT_UID, uid); 225 if (errno != 0) { 226 Log.e(TAG, "setreuid() failed. errno: " + errno); 227 } 228 } 229 230 /** 231 * Sets effective group ID. 232 */ 233 private static void setEffectiveGroup(int gid) { 234 int errno = setregid(ROOT_GID, gid); 235 if (errno != 0) { 236 Log.e(TAG, "setregid() failed. errno: " + errno); 237 } 238 } 239 240 static void preload() { 241 preloadClasses(); 242 preloadResources(); 243 preloadOpenGL(); 244 } 245 246 private static void preloadOpenGL() { 247 if (!SystemProperties.getBoolean(PROPERTY_DISABLE_OPENGL_PRELOADING, false)) { 248 EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY); 249 } 250 } 251 252 /** 253 * Performs Zygote process initialization. Loads and initializes 254 * commonly used classes. 255 * 256 * Most classes only cause a few hundred bytes to be allocated, but 257 * a few will allocate a dozen Kbytes (in one case, 500+K). 258 */ 259 private static void preloadClasses() { 260 final VMRuntime runtime = VMRuntime.getRuntime(); 261 262 InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream( 263 PRELOADED_CLASSES); 264 if (is == null) { 265 Log.e(TAG, "Couldn't find " + PRELOADED_CLASSES + "."); 266 } else { 267 Log.i(TAG, "Preloading classes..."); 268 long startTime = SystemClock.uptimeMillis(); 269 270 // Drop root perms while running static initializers. 271 setEffectiveGroup(UNPRIVILEGED_GID); 272 setEffectiveUser(UNPRIVILEGED_UID); 273 274 // Alter the target heap utilization. With explicit GCs this 275 // is not likely to have any effect. 276 float defaultUtilization = runtime.getTargetHeapUtilization(); 277 runtime.setTargetHeapUtilization(0.8f); 278 279 // Start with a clean slate. 280 System.gc(); 281 runtime.runFinalizationSync(); 282 Debug.startAllocCounting(); 283 284 try { 285 BufferedReader br 286 = new BufferedReader(new InputStreamReader(is), 256); 287 288 int count = 0; 289 String line; 290 while ((line = br.readLine()) != null) { 291 // Skip comments and blank lines. 292 line = line.trim(); 293 if (line.startsWith("#") || line.equals("")) { 294 continue; 295 } 296 297 try { 298 if (false) { 299 Log.v(TAG, "Preloading " + line + "..."); 300 } 301 Class.forName(line); 302 if (Debug.getGlobalAllocSize() > PRELOAD_GC_THRESHOLD) { 303 if (false) { 304 Log.v(TAG, 305 " GC at " + Debug.getGlobalAllocSize()); 306 } 307 System.gc(); 308 runtime.runFinalizationSync(); 309 Debug.resetGlobalAllocSize(); 310 } 311 count++; 312 } catch (ClassNotFoundException e) { 313 Log.w(TAG, "Class not found for preloading: " + line); 314 } catch (UnsatisfiedLinkError e) { 315 Log.w(TAG, "Problem preloading " + line + ": " + e); 316 } catch (Throwable t) { 317 Log.e(TAG, "Error preloading " + line + ".", t); 318 if (t instanceof Error) { 319 throw (Error) t; 320 } 321 if (t instanceof RuntimeException) { 322 throw (RuntimeException) t; 323 } 324 throw new RuntimeException(t); 325 } 326 } 327 328 Log.i(TAG, "...preloaded " + count + " classes in " 329 + (SystemClock.uptimeMillis()-startTime) + "ms."); 330 } catch (IOException e) { 331 Log.e(TAG, "Error reading " + PRELOADED_CLASSES + ".", e); 332 } finally { 333 IoUtils.closeQuietly(is); 334 // Restore default. 335 runtime.setTargetHeapUtilization(defaultUtilization); 336 337 // Fill in dex caches with classes, fields, and methods brought in by preloading. 338 runtime.preloadDexCaches(); 339 340 Debug.stopAllocCounting(); 341 342 // Bring back root. We'll need it later. 343 setEffectiveUser(ROOT_UID); 344 setEffectiveGroup(ROOT_GID); 345 } 346 } 347 } 348 349 /** 350 * Load in commonly used resources, so they can be shared across 351 * processes. 352 * 353 * These tend to be a few Kbytes, but are frequently in the 20-40K 354 * range, and occasionally even larger. 355 */ 356 private static void preloadResources() { 357 final VMRuntime runtime = VMRuntime.getRuntime(); 358 359 Debug.startAllocCounting(); 360 try { 361 System.gc(); 362 runtime.runFinalizationSync(); 363 mResources = Resources.getSystem(); 364 mResources.startPreloading(); 365 if (PRELOAD_RESOURCES) { 366 Log.i(TAG, "Preloading resources..."); 367 368 long startTime = SystemClock.uptimeMillis(); 369 TypedArray ar = mResources.obtainTypedArray( 370 com.android.internal.R.array.preloaded_drawables); 371 int N = preloadDrawables(runtime, ar); 372 ar.recycle(); 373 Log.i(TAG, "...preloaded " + N + " resources in " 374 + (SystemClock.uptimeMillis()-startTime) + "ms."); 375 376 startTime = SystemClock.uptimeMillis(); 377 ar = mResources.obtainTypedArray( 378 com.android.internal.R.array.preloaded_color_state_lists); 379 N = preloadColorStateLists(runtime, ar); 380 ar.recycle(); 381 Log.i(TAG, "...preloaded " + N + " resources in " 382 + (SystemClock.uptimeMillis()-startTime) + "ms."); 383 } 384 mResources.finishPreloading(); 385 } catch (RuntimeException e) { 386 Log.w(TAG, "Failure preloading resources", e); 387 } finally { 388 Debug.stopAllocCounting(); 389 } 390 } 391 392 private static int preloadColorStateLists(VMRuntime runtime, TypedArray ar) { 393 int N = ar.length(); 394 for (int i=0; i<N; i++) { 395 if (Debug.getGlobalAllocSize() > PRELOAD_GC_THRESHOLD) { 396 if (false) { 397 Log.v(TAG, " GC at " + Debug.getGlobalAllocSize()); 398 } 399 System.gc(); 400 runtime.runFinalizationSync(); 401 Debug.resetGlobalAllocSize(); 402 } 403 int id = ar.getResourceId(i, 0); 404 if (false) { 405 Log.v(TAG, "Preloading resource #" + Integer.toHexString(id)); 406 } 407 if (id != 0) { 408 if (mResources.getColorStateList(id) == null) { 409 throw new IllegalArgumentException( 410 "Unable to find preloaded color resource #0x" 411 + Integer.toHexString(id) 412 + " (" + ar.getString(i) + ")"); 413 } 414 } 415 } 416 return N; 417 } 418 419 420 private static int preloadDrawables(VMRuntime runtime, TypedArray ar) { 421 int N = ar.length(); 422 for (int i=0; i<N; i++) { 423 if (Debug.getGlobalAllocSize() > PRELOAD_GC_THRESHOLD) { 424 if (false) { 425 Log.v(TAG, " GC at " + Debug.getGlobalAllocSize()); 426 } 427 System.gc(); 428 runtime.runFinalizationSync(); 429 Debug.resetGlobalAllocSize(); 430 } 431 int id = ar.getResourceId(i, 0); 432 if (false) { 433 Log.v(TAG, "Preloading resource #" + Integer.toHexString(id)); 434 } 435 if (id != 0) { 436 if (mResources.getDrawable(id) == null) { 437 throw new IllegalArgumentException( 438 "Unable to find preloaded drawable resource #0x" 439 + Integer.toHexString(id) 440 + " (" + ar.getString(i) + ")"); 441 } 442 } 443 } 444 return N; 445 } 446 447 /** 448 * Runs several special GCs to try to clean up a few generations of 449 * softly- and final-reachable objects, along with any other garbage. 450 * This is only useful just before a fork(). 451 */ 452 /*package*/ static void gc() { 453 final VMRuntime runtime = VMRuntime.getRuntime(); 454 455 /* runFinalizationSync() lets finalizers be called in Zygote, 456 * which doesn't have a HeapWorker thread. 457 */ 458 System.gc(); 459 runtime.runFinalizationSync(); 460 System.gc(); 461 runtime.runFinalizationSync(); 462 System.gc(); 463 runtime.runFinalizationSync(); 464 } 465 466 /** 467 * Finish remaining work for the newly forked system server process. 468 */ 469 private static void handleSystemServerProcess( 470 ZygoteConnection.Arguments parsedArgs) 471 throws ZygoteInit.MethodAndArgsCaller { 472 473 closeServerSocket(); 474 475 // set umask to 0077 so new files and directories will default to owner-only permissions. 476 Libcore.os.umask(S_IRWXG | S_IRWXO); 477 478 if (parsedArgs.niceName != null) { 479 Process.setArgV0(parsedArgs.niceName); 480 } 481 482 if (parsedArgs.invokeWith != null) { 483 WrapperInit.execApplication(parsedArgs.invokeWith, 484 parsedArgs.niceName, parsedArgs.targetSdkVersion, 485 null, parsedArgs.remainingArgs); 486 } else { 487 /* 488 * Pass the remaining arguments to SystemServer. 489 */ 490 RuntimeInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs); 491 } 492 493 /* should never reach here */ 494 } 495 496 /** 497 * Prepare the arguments and fork for the system server process. 498 */ 499 private static boolean startSystemServer() 500 throws MethodAndArgsCaller, RuntimeException { 501 long capabilities = posixCapabilitiesAsBits( 502 OsConstants.CAP_KILL, 503 OsConstants.CAP_NET_ADMIN, 504 OsConstants.CAP_NET_BIND_SERVICE, 505 OsConstants.CAP_NET_BROADCAST, 506 OsConstants.CAP_NET_RAW, 507 OsConstants.CAP_SYS_MODULE, 508 OsConstants.CAP_SYS_NICE, 509 OsConstants.CAP_SYS_RESOURCE, 510 OsConstants.CAP_SYS_TIME, 511 OsConstants.CAP_SYS_TTY_CONFIG 512 ); 513 /* Hardcoded command line to start the system server */ 514 String args[] = { 515 "--setuid=1000", 516 "--setgid=1000", 517 "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1032,3001,3002,3003,3006,3007", 518 "--capabilities=" + capabilities + "," + capabilities, 519 "--runtime-init", 520 "--nice-name=system_server", 521 "com.android.server.SystemServer", 522 }; 523 ZygoteConnection.Arguments parsedArgs = null; 524 525 int pid; 526 527 try { 528 parsedArgs = new ZygoteConnection.Arguments(args); 529 ZygoteConnection.applyDebuggerSystemProperty(parsedArgs); 530 ZygoteConnection.applyInvokeWithSystemProperty(parsedArgs); 531 532 /* Request to fork the system server process */ 533 pid = Zygote.forkSystemServer( 534 parsedArgs.uid, parsedArgs.gid, 535 parsedArgs.gids, 536 parsedArgs.debugFlags, 537 null, 538 parsedArgs.permittedCapabilities, 539 parsedArgs.effectiveCapabilities); 540 } catch (IllegalArgumentException ex) { 541 throw new RuntimeException(ex); 542 } 543 544 /* For child process */ 545 if (pid == 0) { 546 handleSystemServerProcess(parsedArgs); 547 } 548 549 return true; 550 } 551 552 /** 553 * Gets the bit array representation of the provided list of POSIX capabilities. 554 */ 555 private static long posixCapabilitiesAsBits(int... capabilities) { 556 long result = 0; 557 for (int capability : capabilities) { 558 if ((capability < 0) || (capability > OsConstants.CAP_LAST_CAP)) { 559 throw new IllegalArgumentException(String.valueOf(capability)); 560 } 561 result |= (1L << capability); 562 } 563 return result; 564 } 565 566 public static void main(String argv[]) { 567 try { 568 // Start profiling the zygote initialization. 569 SamplingProfilerIntegration.start(); 570 571 registerZygoteSocket(); 572 EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_START, 573 SystemClock.uptimeMillis()); 574 preload(); 575 EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END, 576 SystemClock.uptimeMillis()); 577 578 // Finish profiling the zygote initialization. 579 SamplingProfilerIntegration.writeZygoteSnapshot(); 580 581 // Do an initial gc to clean up after startup 582 gc(); 583 584 // Disable tracing so that forked processes do not inherit stale tracing tags from 585 // Zygote. 586 Trace.setTracingEnabled(false); 587 588 // If requested, start system server directly from Zygote 589 if (argv.length != 2) { 590 throw new RuntimeException(argv[0] + USAGE_STRING); 591 } 592 593 if (argv[1].equals("start-system-server")) { 594 startSystemServer(); 595 } else if (!argv[1].equals("")) { 596 throw new RuntimeException(argv[0] + USAGE_STRING); 597 } 598 599 Log.i(TAG, "Accepting command socket connections"); 600 601 runSelectLoop(); 602 603 closeServerSocket(); 604 } catch (MethodAndArgsCaller caller) { 605 caller.run(); 606 } catch (RuntimeException ex) { 607 Log.e(TAG, "Zygote died with exception", ex); 608 closeServerSocket(); 609 throw ex; 610 } 611 } 612 613 /** 614 * Runs the zygote process's select loop. Accepts new connections as 615 * they happen, and reads commands from connections one spawn-request's 616 * worth at a time. 617 * 618 * @throws MethodAndArgsCaller in a child process when a main() should 619 * be executed. 620 */ 621 private static void runSelectLoop() throws MethodAndArgsCaller { 622 ArrayList<FileDescriptor> fds = new ArrayList<FileDescriptor>(); 623 ArrayList<ZygoteConnection> peers = new ArrayList<ZygoteConnection>(); 624 FileDescriptor[] fdArray = new FileDescriptor[4]; 625 626 fds.add(sServerSocket.getFileDescriptor()); 627 peers.add(null); 628 629 int loopCount = GC_LOOP_COUNT; 630 while (true) { 631 int index; 632 633 /* 634 * Call gc() before we block in select(). 635 * It's work that has to be done anyway, and it's better 636 * to avoid making every child do it. It will also 637 * madvise() any free memory as a side-effect. 638 * 639 * Don't call it every time, because walking the entire 640 * heap is a lot of overhead to free a few hundred bytes. 641 */ 642 if (loopCount <= 0) { 643 gc(); 644 loopCount = GC_LOOP_COUNT; 645 } else { 646 loopCount--; 647 } 648 649 650 try { 651 fdArray = fds.toArray(fdArray); 652 index = selectReadable(fdArray); 653 } catch (IOException ex) { 654 throw new RuntimeException("Error in select()", ex); 655 } 656 657 if (index < 0) { 658 throw new RuntimeException("Error in select()"); 659 } else if (index == 0) { 660 ZygoteConnection newPeer = acceptCommandPeer(); 661 peers.add(newPeer); 662 fds.add(newPeer.getFileDesciptor()); 663 } else { 664 boolean done; 665 done = peers.get(index).runOnce(); 666 667 if (done) { 668 peers.remove(index); 669 fds.remove(index); 670 } 671 } 672 } 673 } 674 675 /** 676 * The Linux syscall "setreuid()" 677 * @param ruid real uid 678 * @param euid effective uid 679 * @return 0 on success, non-zero errno on fail 680 */ 681 static native int setreuid(int ruid, int euid); 682 683 /** 684 * The Linux syscall "setregid()" 685 * @param rgid real gid 686 * @param egid effective gid 687 * @return 0 on success, non-zero errno on fail 688 */ 689 static native int setregid(int rgid, int egid); 690 691 /** 692 * Invokes the linux syscall "setpgid" 693 * 694 * @param pid pid to change 695 * @param pgid new process group of pid 696 * @return 0 on success or non-zero errno on fail 697 */ 698 static native int setpgid(int pid, int pgid); 699 700 /** 701 * Invokes the linux syscall "getpgid" 702 * 703 * @param pid pid to query 704 * @return pgid of pid in question 705 * @throws IOException on error 706 */ 707 static native int getpgid(int pid) throws IOException; 708 709 /** 710 * Invokes the syscall dup2() to copy the specified descriptors into 711 * stdin, stdout, and stderr. The existing stdio descriptors will be 712 * closed and errors during close will be ignored. The specified 713 * descriptors will also remain open at their original descriptor numbers, 714 * so the caller may want to close the original descriptors. 715 * 716 * @param in new stdin 717 * @param out new stdout 718 * @param err new stderr 719 * @throws IOException 720 */ 721 static native void reopenStdio(FileDescriptor in, 722 FileDescriptor out, FileDescriptor err) throws IOException; 723 724 /** 725 * Toggles the close-on-exec flag for the specified file descriptor. 726 * 727 * @param fd non-null; file descriptor 728 * @param flag desired close-on-exec flag state 729 * @throws IOException 730 */ 731 static native void setCloseOnExec(FileDescriptor fd, boolean flag) 732 throws IOException; 733 734 /** 735 * Invokes select() on the provider array of file descriptors (selecting 736 * for readability only). Array elements of null are ignored. 737 * 738 * @param fds non-null; array of readable file descriptors 739 * @return index of descriptor that is now readable or -1 for empty array. 740 * @throws IOException if an error occurs 741 */ 742 static native int selectReadable(FileDescriptor[] fds) throws IOException; 743 744 /** 745 * Creates a file descriptor from an int fd. 746 * 747 * @param fd integer OS file descriptor 748 * @return non-null; FileDescriptor instance 749 * @throws IOException if fd is invalid 750 */ 751 static native FileDescriptor createFileDescriptor(int fd) 752 throws IOException; 753 754 /** 755 * Class not instantiable. 756 */ 757 private ZygoteInit() { 758 } 759 760 /** 761 * Helper exception class which holds a method and arguments and 762 * can call them. This is used as part of a trampoline to get rid of 763 * the initial process setup stack frames. 764 */ 765 public static class MethodAndArgsCaller extends Exception 766 implements Runnable { 767 /** method to call */ 768 private final Method mMethod; 769 770 /** argument array */ 771 private final String[] mArgs; 772 773 public MethodAndArgsCaller(Method method, String[] args) { 774 mMethod = method; 775 mArgs = args; 776 } 777 778 public void run() { 779 try { 780 mMethod.invoke(null, new Object[] { mArgs }); 781 } catch (IllegalAccessException ex) { 782 throw new RuntimeException(ex); 783 } catch (InvocationTargetException ex) { 784 Throwable cause = ex.getCause(); 785 if (cause instanceof RuntimeException) { 786 throw (RuntimeException) cause; 787 } else if (cause instanceof Error) { 788 throw (Error) cause; 789 } 790 throw new RuntimeException(ex); 791 } 792 } 793 } 794} 795