com_android_internal_os_Zygote.cpp revision df781cc5147c07f1d28b78806b3578a2ff571497
1/* 2 * Copyright (C) 2008 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 17#define LOG_TAG "Zygote" 18 19// sys/mount.h has to come before linux/fs.h due to redefinition of MS_RDONLY, MS_BIND, etc 20#include <sys/mount.h> 21#include <linux/fs.h> 22 23#include <list> 24#include <sstream> 25#include <string> 26 27#include <fcntl.h> 28#include <grp.h> 29#include <inttypes.h> 30#include <mntent.h> 31#include <paths.h> 32#include <signal.h> 33#include <stdlib.h> 34#include <sys/capability.h> 35#include <sys/cdefs.h> 36#include <sys/personality.h> 37#include <sys/prctl.h> 38#include <sys/resource.h> 39#include <sys/stat.h> 40#include <sys/time.h> 41#include <sys/types.h> 42#include <sys/utsname.h> 43#include <sys/wait.h> 44#include <unistd.h> 45 46#include <cutils/fs.h> 47#include <cutils/multiuser.h> 48#include <cutils/sched_policy.h> 49#include <private/android_filesystem_config.h> 50#include <utils/String8.h> 51#include <selinux/android.h> 52#include <processgroup/processgroup.h> 53 54#include "core_jni_helpers.h" 55#include "JNIHelp.h" 56#include "ScopedLocalRef.h" 57#include "ScopedPrimitiveArray.h" 58#include "ScopedUtfChars.h" 59#include "fd_utils.h" 60 61#include "nativebridge/native_bridge.h" 62 63namespace { 64 65using android::String8; 66 67static pid_t gSystemServerPid = 0; 68 69static const char kZygoteClassName[] = "com/android/internal/os/Zygote"; 70static jclass gZygoteClass; 71static jmethodID gCallPostForkChildHooks; 72 73// Must match values in com.android.internal.os.Zygote. 74enum MountExternalKind { 75 MOUNT_EXTERNAL_NONE = 0, 76 MOUNT_EXTERNAL_DEFAULT = 1, 77 MOUNT_EXTERNAL_READ = 2, 78 MOUNT_EXTERNAL_WRITE = 3, 79}; 80 81static void RuntimeAbort(JNIEnv* env, int line, const char* msg) { 82 std::ostringstream oss; 83 oss << __FILE__ << ":" << line << ": " << msg; 84 env->FatalError(oss.str().c_str()); 85} 86 87// This signal handler is for zygote mode, since the zygote must reap its children 88static void SigChldHandler(int /*signal_number*/) { 89 pid_t pid; 90 int status; 91 92 // It's necessary to save and restore the errno during this function. 93 // Since errno is stored per thread, changing it here modifies the errno 94 // on the thread on which this signal handler executes. If a signal occurs 95 // between a call and an errno check, it's possible to get the errno set 96 // here. 97 // See b/23572286 for extra information. 98 int saved_errno = errno; 99 100 while ((pid = waitpid(-1, &status, WNOHANG)) > 0) { 101 // Log process-death status that we care about. In general it is 102 // not safe to call LOG(...) from a signal handler because of 103 // possible reentrancy. However, we know a priori that the 104 // current implementation of LOG() is safe to call from a SIGCHLD 105 // handler in the zygote process. If the LOG() implementation 106 // changes its locking strategy or its use of syscalls within the 107 // lazy-init critical section, its use here may become unsafe. 108 if (WIFEXITED(status)) { 109 if (WEXITSTATUS(status)) { 110 ALOGI("Process %d exited cleanly (%d)", pid, WEXITSTATUS(status)); 111 } 112 } else if (WIFSIGNALED(status)) { 113 if (WTERMSIG(status) != SIGKILL) { 114 ALOGI("Process %d exited due to signal (%d)", pid, WTERMSIG(status)); 115 } 116 if (WCOREDUMP(status)) { 117 ALOGI("Process %d dumped core.", pid); 118 } 119 } 120 121 // If the just-crashed process is the system_server, bring down zygote 122 // so that it is restarted by init and system server will be restarted 123 // from there. 124 if (pid == gSystemServerPid) { 125 ALOGE("Exit zygote because system server (%d) has terminated", pid); 126 kill(getpid(), SIGKILL); 127 } 128 } 129 130 // Note that we shouldn't consider ECHILD an error because 131 // the secondary zygote might have no children left to wait for. 132 if (pid < 0 && errno != ECHILD) { 133 ALOGW("Zygote SIGCHLD error in waitpid: %s", strerror(errno)); 134 } 135 136 errno = saved_errno; 137} 138 139// Configures the SIGCHLD handler for the zygote process. This is configured 140// very late, because earlier in the runtime we may fork() and exec() 141// other processes, and we want to waitpid() for those rather than 142// have them be harvested immediately. 143// 144// This ends up being called repeatedly before each fork(), but there's 145// no real harm in that. 146static void SetSigChldHandler() { 147 struct sigaction sa; 148 memset(&sa, 0, sizeof(sa)); 149 sa.sa_handler = SigChldHandler; 150 151 int err = sigaction(SIGCHLD, &sa, NULL); 152 if (err < 0) { 153 ALOGW("Error setting SIGCHLD handler: %s", strerror(errno)); 154 } 155} 156 157// Resets nice priority for zygote process. Zygote priority can be set 158// to high value during boot phase to speed it up. We want to ensure 159// zygote is running at normal priority before childs are forked from it. 160// 161// This ends up being called repeatedly before each fork(), but there's 162// no real harm in that. 163static void ResetNicePriority(JNIEnv* env) { 164 errno = 0; 165 int prio = getpriority(PRIO_PROCESS, 0); 166 if (prio == -1 && errno != 0) { 167 ALOGW("getpriority failed: %s\n", strerror(errno)); 168 } 169 if (prio != 0 && setpriority(PRIO_PROCESS, 0, 0) != 0) { 170 ALOGE("setpriority(%d, 0, 0) failed: %s", PRIO_PROCESS, strerror(errno)); 171 RuntimeAbort(env, __LINE__, "setpriority failed"); 172 } 173} 174 175// Sets the SIGCHLD handler back to default behavior in zygote children. 176static void UnsetSigChldHandler() { 177 struct sigaction sa; 178 memset(&sa, 0, sizeof(sa)); 179 sa.sa_handler = SIG_DFL; 180 181 int err = sigaction(SIGCHLD, &sa, NULL); 182 if (err < 0) { 183 ALOGW("Error unsetting SIGCHLD handler: %s", strerror(errno)); 184 } 185} 186 187// Calls POSIX setgroups() using the int[] object as an argument. 188// A NULL argument is tolerated. 189static void SetGids(JNIEnv* env, jintArray javaGids) { 190 if (javaGids == NULL) { 191 return; 192 } 193 194 ScopedIntArrayRO gids(env, javaGids); 195 if (gids.get() == NULL) { 196 RuntimeAbort(env, __LINE__, "Getting gids int array failed"); 197 } 198 int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0])); 199 if (rc == -1) { 200 std::ostringstream oss; 201 oss << "setgroups failed: " << strerror(errno) << ", gids.size=" << gids.size(); 202 RuntimeAbort(env, __LINE__, oss.str().c_str()); 203 } 204} 205 206// Sets the resource limits via setrlimit(2) for the values in the 207// two-dimensional array of integers that's passed in. The second dimension 208// contains a tuple of length 3: (resource, rlim_cur, rlim_max). NULL is 209// treated as an empty array. 210static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) { 211 if (javaRlimits == NULL) { 212 return; 213 } 214 215 rlimit rlim; 216 memset(&rlim, 0, sizeof(rlim)); 217 218 for (int i = 0; i < env->GetArrayLength(javaRlimits); ++i) { 219 ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i)); 220 ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get())); 221 if (javaRlimit.size() != 3) { 222 RuntimeAbort(env, __LINE__, "rlimits array must have a second dimension of size 3"); 223 } 224 225 rlim.rlim_cur = javaRlimit[1]; 226 rlim.rlim_max = javaRlimit[2]; 227 228 int rc = setrlimit(javaRlimit[0], &rlim); 229 if (rc == -1) { 230 ALOGE("setrlimit(%d, {%ld, %ld}) failed", javaRlimit[0], rlim.rlim_cur, 231 rlim.rlim_max); 232 RuntimeAbort(env, __LINE__, "setrlimit failed"); 233 } 234 } 235} 236 237// The debug malloc library needs to know whether it's the zygote or a child. 238extern "C" int gMallocLeakZygoteChild; 239 240static void EnableKeepCapabilities(JNIEnv* env) { 241 int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0); 242 if (rc == -1) { 243 RuntimeAbort(env, __LINE__, "prctl(PR_SET_KEEPCAPS) failed"); 244 } 245} 246 247static void DropCapabilitiesBoundingSet(JNIEnv* env) { 248 for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) { 249 int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0); 250 if (rc == -1) { 251 if (errno == EINVAL) { 252 ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify " 253 "your kernel is compiled with file capabilities support"); 254 } else { 255 RuntimeAbort(env, __LINE__, "prctl(PR_CAPBSET_DROP) failed"); 256 } 257 } 258 } 259} 260 261static void SetCapabilities(JNIEnv* env, int64_t permitted, int64_t effective) { 262 __user_cap_header_struct capheader; 263 memset(&capheader, 0, sizeof(capheader)); 264 capheader.version = _LINUX_CAPABILITY_VERSION_3; 265 capheader.pid = 0; 266 267 __user_cap_data_struct capdata[2]; 268 memset(&capdata, 0, sizeof(capdata)); 269 capdata[0].effective = effective; 270 capdata[1].effective = effective >> 32; 271 capdata[0].permitted = permitted; 272 capdata[1].permitted = permitted >> 32; 273 274 if (capset(&capheader, &capdata[0]) == -1) { 275 ALOGE("capset(%" PRId64 ", %" PRId64 ") failed", permitted, effective); 276 RuntimeAbort(env, __LINE__, "capset failed"); 277 } 278} 279 280static void SetSchedulerPolicy(JNIEnv* env) { 281 errno = -set_sched_policy(0, SP_DEFAULT); 282 if (errno != 0) { 283 ALOGE("set_sched_policy(0, SP_DEFAULT) failed"); 284 RuntimeAbort(env, __LINE__, "set_sched_policy(0, SP_DEFAULT) failed"); 285 } 286} 287 288static int UnmountTree(const char* path) { 289 size_t path_len = strlen(path); 290 291 FILE* fp = setmntent("/proc/mounts", "r"); 292 if (fp == NULL) { 293 ALOGE("Error opening /proc/mounts: %s", strerror(errno)); 294 return -errno; 295 } 296 297 // Some volumes can be stacked on each other, so force unmount in 298 // reverse order to give us the best chance of success. 299 std::list<std::string> toUnmount; 300 mntent* mentry; 301 while ((mentry = getmntent(fp)) != NULL) { 302 if (strncmp(mentry->mnt_dir, path, path_len) == 0) { 303 toUnmount.push_front(std::string(mentry->mnt_dir)); 304 } 305 } 306 endmntent(fp); 307 308 for (auto path : toUnmount) { 309 if (umount2(path.c_str(), MNT_DETACH)) { 310 ALOGW("Failed to unmount %s: %s", path.c_str(), strerror(errno)); 311 } 312 } 313 return 0; 314} 315 316// Create a private mount namespace and bind mount appropriate emulated 317// storage for the given user. 318static bool MountEmulatedStorage(uid_t uid, jint mount_mode, 319 bool force_mount_namespace) { 320 // See storage config details at http://source.android.com/tech/storage/ 321 322 String8 storageSource; 323 if (mount_mode == MOUNT_EXTERNAL_DEFAULT) { 324 storageSource = "/mnt/runtime/default"; 325 } else if (mount_mode == MOUNT_EXTERNAL_READ) { 326 storageSource = "/mnt/runtime/read"; 327 } else if (mount_mode == MOUNT_EXTERNAL_WRITE) { 328 storageSource = "/mnt/runtime/write"; 329 } else if (!force_mount_namespace) { 330 // Sane default of no storage visible 331 return true; 332 } 333 334 // Create a second private mount namespace for our process 335 if (unshare(CLONE_NEWNS) == -1) { 336 ALOGW("Failed to unshare(): %s", strerror(errno)); 337 return false; 338 } 339 340 if (TEMP_FAILURE_RETRY(mount(storageSource.string(), "/storage", 341 NULL, MS_BIND | MS_REC | MS_SLAVE, NULL)) == -1) { 342 ALOGW("Failed to mount %s to /storage: %s", storageSource.string(), strerror(errno)); 343 return false; 344 } 345 346 // Mount user-specific symlink helper into place 347 userid_t user_id = multiuser_get_user_id(uid); 348 const String8 userSource(String8::format("/mnt/user/%d", user_id)); 349 if (fs_prepare_dir(userSource.string(), 0751, 0, 0) == -1) { 350 return false; 351 } 352 if (TEMP_FAILURE_RETRY(mount(userSource.string(), "/storage/self", 353 NULL, MS_BIND, NULL)) == -1) { 354 ALOGW("Failed to mount %s to /storage/self: %s", userSource.string(), strerror(errno)); 355 return false; 356 } 357 358 return true; 359} 360 361static bool NeedsNoRandomizeWorkaround() { 362#if !defined(__arm__) 363 return false; 364#else 365 int major; 366 int minor; 367 struct utsname uts; 368 if (uname(&uts) == -1) { 369 return false; 370 } 371 372 if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) { 373 return false; 374 } 375 376 // Kernels before 3.4.* need the workaround. 377 return (major < 3) || ((major == 3) && (minor < 4)); 378#endif 379} 380 381// Utility to close down the Zygote socket file descriptors while 382// the child is still running as root with Zygote's privileges. Each 383// descriptor (if any) is closed via dup2(), replacing it with a valid 384// (open) descriptor to /dev/null. 385 386static void DetachDescriptors(JNIEnv* env, jintArray fdsToClose) { 387 if (!fdsToClose) { 388 return; 389 } 390 jsize count = env->GetArrayLength(fdsToClose); 391 ScopedIntArrayRO ar(env, fdsToClose); 392 if (ar.get() == NULL) { 393 RuntimeAbort(env, __LINE__, "Bad fd array"); 394 } 395 jsize i; 396 int devnull; 397 for (i = 0; i < count; i++) { 398 devnull = open("/dev/null", O_RDWR); 399 if (devnull < 0) { 400 ALOGE("Failed to open /dev/null: %s", strerror(errno)); 401 RuntimeAbort(env, __LINE__, "Failed to open /dev/null"); 402 continue; 403 } 404 ALOGV("Switching descriptor %d to /dev/null: %s", ar[i], strerror(errno)); 405 if (dup2(devnull, ar[i]) < 0) { 406 ALOGE("Failed dup2() on descriptor %d: %s", ar[i], strerror(errno)); 407 RuntimeAbort(env, __LINE__, "Failed dup2()"); 408 } 409 close(devnull); 410 } 411} 412 413void SetThreadName(const char* thread_name) { 414 bool hasAt = false; 415 bool hasDot = false; 416 const char* s = thread_name; 417 while (*s) { 418 if (*s == '.') { 419 hasDot = true; 420 } else if (*s == '@') { 421 hasAt = true; 422 } 423 s++; 424 } 425 const int len = s - thread_name; 426 if (len < 15 || hasAt || !hasDot) { 427 s = thread_name; 428 } else { 429 s = thread_name + len - 15; 430 } 431 // pthread_setname_np fails rather than truncating long strings. 432 char buf[16]; // MAX_TASK_COMM_LEN=16 is hard-coded into bionic 433 strlcpy(buf, s, sizeof(buf)-1); 434 errno = pthread_setname_np(pthread_self(), buf); 435 if (errno != 0) { 436 ALOGW("Unable to set the name of current thread to '%s': %s", buf, strerror(errno)); 437 } 438} 439 440// The list of open zygote file descriptors. 441static FileDescriptorTable* gOpenFdTable = NULL; 442 443// Utility routine to fork zygote and specialize the child process. 444static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids, 445 jint debug_flags, jobjectArray javaRlimits, 446 jlong permittedCapabilities, jlong effectiveCapabilities, 447 jint mount_external, 448 jstring java_se_info, jstring java_se_name, 449 bool is_system_server, jintArray fdsToClose, 450 jstring instructionSet, jstring dataDir) { 451 SetSigChldHandler(); 452 453 sigset_t sigchld; 454 sigemptyset(&sigchld); 455 sigaddset(&sigchld, SIGCHLD); 456 457 // Temporarily block SIGCHLD during forks. The SIGCHLD handler might 458 // log, which would result in the logging FDs we close being reopened. 459 // This would cause failures because the FDs are not whitelisted. 460 // 461 // Note that the zygote process is single threaded at this point. 462 if (sigprocmask(SIG_BLOCK, &sigchld, nullptr) == -1) { 463 ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)); 464 RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_BLOCK, { SIGCHLD }) failed."); 465 } 466 467 // Close any logging related FDs before we start evaluating the list of 468 // file descriptors. 469 __android_log_close(); 470 471 // If this is the first fork for this zygote, create the open FD table. 472 // If it isn't, we just need to check whether the list of open files has 473 // changed (and it shouldn't in the normal case). 474 if (gOpenFdTable == NULL) { 475 gOpenFdTable = FileDescriptorTable::Create(); 476 if (gOpenFdTable == NULL) { 477 RuntimeAbort(env, __LINE__, "Unable to construct file descriptor table."); 478 } 479 } else if (!gOpenFdTable->Restat()) { 480 RuntimeAbort(env, __LINE__, "Unable to restat file descriptor table."); 481 } 482 483 ResetNicePriority(env); 484 485 pid_t pid = fork(); 486 487 if (pid == 0) { 488 // The child process. 489 gMallocLeakZygoteChild = 1; 490 491 // Clean up any descriptors which must be closed immediately 492 DetachDescriptors(env, fdsToClose); 493 494 // Re-open all remaining open file descriptors so that they aren't shared 495 // with the zygote across a fork. 496 if (!gOpenFdTable->ReopenOrDetach()) { 497 RuntimeAbort(env, __LINE__, "Unable to reopen whitelisted descriptors."); 498 } 499 500 if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) { 501 ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)); 502 RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed."); 503 } 504 505 // Keep capabilities across UID change, unless we're staying root. 506 if (uid != 0) { 507 EnableKeepCapabilities(env); 508 } 509 510 DropCapabilitiesBoundingSet(env); 511 512 bool use_native_bridge = !is_system_server && (instructionSet != NULL) 513 && android::NativeBridgeAvailable(); 514 if (use_native_bridge) { 515 ScopedUtfChars isa_string(env, instructionSet); 516 use_native_bridge = android::NeedsNativeBridge(isa_string.c_str()); 517 } 518 if (use_native_bridge && dataDir == NULL) { 519 // dataDir should never be null if we need to use a native bridge. 520 // In general, dataDir will never be null for normal applications. It can only happen in 521 // special cases (for isolated processes which are not associated with any app). These are 522 // launched by the framework and should not be emulated anyway. 523 use_native_bridge = false; 524 ALOGW("Native bridge will not be used because dataDir == NULL."); 525 } 526 527 if (!MountEmulatedStorage(uid, mount_external, use_native_bridge)) { 528 ALOGW("Failed to mount emulated storage: %s", strerror(errno)); 529 if (errno == ENOTCONN || errno == EROFS) { 530 // When device is actively encrypting, we get ENOTCONN here 531 // since FUSE was mounted before the framework restarted. 532 // When encrypted device is booting, we get EROFS since 533 // FUSE hasn't been created yet by init. 534 // In either case, continue without external storage. 535 } else { 536 RuntimeAbort(env, __LINE__, "Cannot continue without emulated storage"); 537 } 538 } 539 540 if (!is_system_server) { 541 int rc = createProcessGroup(uid, getpid()); 542 if (rc != 0) { 543 if (rc == -EROFS) { 544 ALOGW("createProcessGroup failed, kernel missing CONFIG_CGROUP_CPUACCT?"); 545 } else { 546 ALOGE("createProcessGroup(%d, %d) failed: %s", uid, pid, strerror(-rc)); 547 } 548 } 549 } 550 551 SetGids(env, javaGids); 552 553 SetRLimits(env, javaRlimits); 554 555 if (use_native_bridge) { 556 ScopedUtfChars isa_string(env, instructionSet); 557 ScopedUtfChars data_dir(env, dataDir); 558 android::PreInitializeNativeBridge(data_dir.c_str(), isa_string.c_str()); 559 } 560 561 int rc = setresgid(gid, gid, gid); 562 if (rc == -1) { 563 ALOGE("setresgid(%d) failed: %s", gid, strerror(errno)); 564 RuntimeAbort(env, __LINE__, "setresgid failed"); 565 } 566 567 rc = setresuid(uid, uid, uid); 568 if (rc == -1) { 569 ALOGE("setresuid(%d) failed: %s", uid, strerror(errno)); 570 RuntimeAbort(env, __LINE__, "setresuid failed"); 571 } 572 573 if (NeedsNoRandomizeWorkaround()) { 574 // Work around ARM kernel ASLR lossage (http://b/5817320). 575 int old_personality = personality(0xffffffff); 576 int new_personality = personality(old_personality | ADDR_NO_RANDOMIZE); 577 if (new_personality == -1) { 578 ALOGW("personality(%d) failed: %s", new_personality, strerror(errno)); 579 } 580 } 581 582 SetCapabilities(env, permittedCapabilities, effectiveCapabilities); 583 584 SetSchedulerPolicy(env); 585 586 const char* se_info_c_str = NULL; 587 ScopedUtfChars* se_info = NULL; 588 if (java_se_info != NULL) { 589 se_info = new ScopedUtfChars(env, java_se_info); 590 se_info_c_str = se_info->c_str(); 591 if (se_info_c_str == NULL) { 592 RuntimeAbort(env, __LINE__, "se_info_c_str == NULL"); 593 } 594 } 595 const char* se_name_c_str = NULL; 596 ScopedUtfChars* se_name = NULL; 597 if (java_se_name != NULL) { 598 se_name = new ScopedUtfChars(env, java_se_name); 599 se_name_c_str = se_name->c_str(); 600 if (se_name_c_str == NULL) { 601 RuntimeAbort(env, __LINE__, "se_name_c_str == NULL"); 602 } 603 } 604 rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str); 605 if (rc == -1) { 606 ALOGE("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed", uid, 607 is_system_server, se_info_c_str, se_name_c_str); 608 RuntimeAbort(env, __LINE__, "selinux_android_setcontext failed"); 609 } 610 611 // Make it easier to debug audit logs by setting the main thread's name to the 612 // nice name rather than "app_process". 613 if (se_info_c_str == NULL && is_system_server) { 614 se_name_c_str = "system_server"; 615 } 616 if (se_info_c_str != NULL) { 617 SetThreadName(se_name_c_str); 618 } 619 620 delete se_info; 621 delete se_name; 622 623 UnsetSigChldHandler(); 624 625 env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, debug_flags, 626 is_system_server, instructionSet); 627 if (env->ExceptionCheck()) { 628 RuntimeAbort(env, __LINE__, "Error calling post fork hooks."); 629 } 630 } else if (pid > 0) { 631 // the parent process 632 633 // We blocked SIGCHLD prior to a fork, we unblock it here. 634 if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) { 635 ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)); 636 RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed."); 637 } 638 } 639 return pid; 640} 641} // anonymous namespace 642 643namespace android { 644 645static jint com_android_internal_os_Zygote_nativeForkAndSpecialize( 646 JNIEnv* env, jclass, jint uid, jint gid, jintArray gids, 647 jint debug_flags, jobjectArray rlimits, 648 jint mount_external, jstring se_info, jstring se_name, 649 jintArray fdsToClose, jstring instructionSet, jstring appDataDir) { 650 jlong capabilities = 0; 651 652 // Grant CAP_WAKE_ALARM to the Bluetooth process. 653 // Additionally, allow bluetooth to open packet sockets so it can start the DHCP client. 654 // TODO: consider making such functionality an RPC to netd. 655 if (multiuser_get_app_id(uid) == AID_BLUETOOTH) { 656 capabilities |= (1LL << CAP_WAKE_ALARM); 657 capabilities |= (1LL << CAP_NET_RAW); 658 capabilities |= (1LL << CAP_NET_BIND_SERVICE); 659 } 660 661 // Grant CAP_BLOCK_SUSPEND to processes that belong to GID "wakelock" 662 bool gid_wakelock_found = false; 663 if (gid == AID_WAKELOCK) { 664 gid_wakelock_found = true; 665 } else if (gids != NULL) { 666 jsize gids_num = env->GetArrayLength(gids); 667 ScopedIntArrayRO ar(env, gids); 668 if (ar.get() == NULL) { 669 RuntimeAbort(env, __LINE__, "Bad gids array"); 670 } 671 for (int i = 0; i < gids_num; i++) { 672 if (ar[i] == AID_WAKELOCK) { 673 gid_wakelock_found = true; 674 break; 675 } 676 } 677 } 678 if (gid_wakelock_found) { 679 capabilities |= (1LL << CAP_BLOCK_SUSPEND); 680 } 681 682 return ForkAndSpecializeCommon(env, uid, gid, gids, debug_flags, 683 rlimits, capabilities, capabilities, mount_external, se_info, 684 se_name, false, fdsToClose, instructionSet, appDataDir); 685} 686 687static jint com_android_internal_os_Zygote_nativeForkSystemServer( 688 JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids, 689 jint debug_flags, jobjectArray rlimits, jlong permittedCapabilities, 690 jlong effectiveCapabilities) { 691 pid_t pid = ForkAndSpecializeCommon(env, uid, gid, gids, 692 debug_flags, rlimits, 693 permittedCapabilities, effectiveCapabilities, 694 MOUNT_EXTERNAL_DEFAULT, NULL, NULL, true, NULL, 695 NULL, NULL); 696 if (pid > 0) { 697 // The zygote process checks whether the child process has died or not. 698 ALOGI("System server process %d has been created", pid); 699 gSystemServerPid = pid; 700 // There is a slight window that the system server process has crashed 701 // but it went unnoticed because we haven't published its pid yet. So 702 // we recheck here just to make sure that all is well. 703 int status; 704 if (waitpid(pid, &status, WNOHANG) == pid) { 705 ALOGE("System server process %d has died. Restarting Zygote!", pid); 706 RuntimeAbort(env, __LINE__, "System server process has died. Restarting Zygote!"); 707 } 708 } 709 return pid; 710} 711 712static void com_android_internal_os_Zygote_nativeAllowFileAcrossFork( 713 JNIEnv* env, jclass, jstring path) { 714 ScopedUtfChars path_native(env, path); 715 const char* path_cstr = path_native.c_str(); 716 if (!path_cstr) { 717 RuntimeAbort(env, __LINE__, "path_cstr == NULL"); 718 } 719 FileDescriptorWhitelist::Get()->Allow(path_cstr); 720} 721 722static void com_android_internal_os_Zygote_nativeUnmountStorageOnInit(JNIEnv* env, jclass) { 723 // Zygote process unmount root storage space initially before every child processes are forked. 724 // Every forked child processes (include SystemServer) only mount their own root storage space 725 // and no need unmount storage operation in MountEmulatedStorage method. 726 // Zygote process does not utilize root storage spaces and unshares its mount namespace below. 727 728 // See storage config details at http://source.android.com/tech/storage/ 729 // Create private mount namespace shared by all children 730 if (unshare(CLONE_NEWNS) == -1) { 731 RuntimeAbort(env, __LINE__, "Failed to unshare()"); 732 return; 733 } 734 735 // Mark rootfs as being a slave so that changes from default 736 // namespace only flow into our children. 737 if (mount("rootfs", "/", nullptr, (MS_SLAVE | MS_REC), nullptr) == -1) { 738 RuntimeAbort(env, __LINE__, "Failed to mount() rootfs as MS_SLAVE"); 739 return; 740 } 741 742 // Create a staging tmpfs that is shared by our children; they will 743 // bind mount storage into their respective private namespaces, which 744 // are isolated from each other. 745 const char* target_base = getenv("EMULATED_STORAGE_TARGET"); 746 if (target_base != nullptr) { 747#define STRINGIFY_UID(x) __STRING(x) 748 if (mount("tmpfs", target_base, "tmpfs", MS_NOSUID | MS_NODEV, 749 "uid=0,gid=" STRINGIFY_UID(AID_SDCARD_R) ",mode=0751") == -1) { 750 ALOGE("Failed to mount tmpfs to %s", target_base); 751 RuntimeAbort(env, __LINE__, "Failed to mount tmpfs"); 752 return; 753 } 754#undef STRINGIFY_UID 755 } 756 757 UnmountTree("/storage"); 758} 759 760static const JNINativeMethod gMethods[] = { 761 { "nativeForkAndSpecialize", 762 "(II[II[[IILjava/lang/String;Ljava/lang/String;[ILjava/lang/String;Ljava/lang/String;)I", 763 (void *) com_android_internal_os_Zygote_nativeForkAndSpecialize }, 764 { "nativeForkSystemServer", "(II[II[[IJJ)I", 765 (void *) com_android_internal_os_Zygote_nativeForkSystemServer }, 766 { "nativeAllowFileAcrossFork", "(Ljava/lang/String;)V", 767 (void *) com_android_internal_os_Zygote_nativeAllowFileAcrossFork }, 768 { "nativeUnmountStorageOnInit", "()V", 769 (void *) com_android_internal_os_Zygote_nativeUnmountStorageOnInit } 770}; 771 772int register_com_android_internal_os_Zygote(JNIEnv* env) { 773 gZygoteClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteClassName)); 774 gCallPostForkChildHooks = GetStaticMethodIDOrDie(env, gZygoteClass, "callPostForkChildHooks", 775 "(IZLjava/lang/String;)V"); 776 777 return RegisterMethodsOrDie(env, "com/android/internal/os/Zygote", gMethods, NELEM(gMethods)); 778} 779} // namespace android 780