Merge changes I14df050f,I55c30f78,I269eae0f (3dd16b1e) · Commits · e / os / android_frameworks_base

core/jni/com_android_internal_os_Zygote.cpp

+136 −78

Original line number	Diff line number	Diff line
		@@ -71,6 +71,9 @@ using android::String8;
		using android::base::StringPrintf;
		using android::base::WriteStringToFile;

		#define CREATE_ERROR(...) StringPrintf("%s:%d: ", __FILE__, __LINE__). \
		append(StringPrintf(__VA_ARGS__))

		static pid_t gSystemServerPid = 0;

		static const char kZygoteClassName[] = "com/android/internal/os/Zygote";
		@@ -186,30 +189,32 @@ static void UnsetChldSignalHandler() {

		// Calls POSIX setgroups() using the int[] object as an argument.
		// A NULL argument is tolerated.
		static void SetGids(JNIEnv* env, jintArray javaGids) {
		static bool SetGids(JNIEnv* env, jintArray javaGids, std::string* error_msg) {
		if (javaGids == NULL) {
		return;
		return true;
		}

		ScopedIntArrayRO gids(env, javaGids);
		if (gids.get() == NULL) {
		RuntimeAbort(env, __LINE__, "Getting gids int array failed");
		*error_msg = CREATE_ERROR("Getting gids int array failed");
		return false;
		}
		int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0]));
		if (rc == -1) {
		std::ostringstream oss;
		oss << "setgroups failed: " << strerror(errno) << ", gids.size=" << gids.size();
		RuntimeAbort(env, __LINE__, oss.str().c_str());
		*error_msg = CREATE_ERROR("setgroups failed: %s, gids.size=%zu", strerror(errno), gids.size());
		return false;
		}

		return true;
		}

		// Sets the resource limits via setrlimit(2) for the values in the
		// two-dimensional array of integers that's passed in. The second dimension
		// contains a tuple of length 3: (resource, rlim_cur, rlim_max). NULL is
		// treated as an empty array.
		static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) {
		static bool SetRLimits(JNIEnv* env, jobjectArray javaRlimits, std::string* error_msg) {
		if (javaRlimits == NULL) {
		return;
		return true;
		}

		rlimit rlim;
		@@ -219,7 +224,8 @@ static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) {
		ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i));
		ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get()));
		if (javaRlimit.size() != 3) {
		RuntimeAbort(env, __LINE__, "rlimits array must have a second dimension of size 3");
		*error_msg = CREATE_ERROR("rlimits array must have a second dimension of size 3");
		return false;
		}

		rlim.rlim_cur = javaRlimit[1];
		@@ -227,11 +233,13 @@ static void SetRLimits(JNIEnv* env, jobjectArray javaRlimits) {

		int rc = setrlimit(javaRlimit[0], &rlim);
		if (rc == -1) {
		ALOGE("setrlimit(%d, {%ld, %ld}) failed", javaRlimit[0], rlim.rlim_cur,
		*error_msg = CREATE_ERROR("setrlimit(%d, {%ld, %ld}) failed", javaRlimit[0], rlim.rlim_cur,
		rlim.rlim_max);
		RuntimeAbort(env, __LINE__, "setrlimit failed");
		return false;
		}
		}

		return true;
		}

		// The debug malloc library needs to know whether it's the zygote or a child.
		@@ -259,14 +267,16 @@ static void SetUpSeccompFilter(uid_t uid) {
		}
		}

		static void EnableKeepCapabilities(JNIEnv* env) {
		static bool EnableKeepCapabilities(std::string* error_msg) {
		int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
		if (rc == -1) {
		RuntimeAbort(env, __LINE__, "prctl(PR_SET_KEEPCAPS) failed");
		*error_msg = CREATE_ERROR("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
		return false;
		}
		return true;
		}

		static void DropCapabilitiesBoundingSet(JNIEnv* env) {
		static bool DropCapabilitiesBoundingSet(std::string* error_msg) {
		for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {
		int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0);
		if (rc == -1) {
		@@ -274,14 +284,15 @@ static void DropCapabilitiesBoundingSet(JNIEnv* env) {
		ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
		"your kernel is compiled with file capabilities support");
		} else {
		ALOGE("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno));
		RuntimeAbort(env, __LINE__, "prctl(PR_CAPBSET_DROP) failed");
		*error_msg = CREATE_ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno));
		return false;
		}
		}
		}
		return true;
		}

		static void SetInheritable(JNIEnv* env, uint64_t inheritable) {
		static bool SetInheritable(uint64_t inheritable, std::string* error_msg) {
		__user_cap_header_struct capheader;
		memset(&capheader, 0, sizeof(capheader));
		capheader.version = _LINUX_CAPABILITY_VERSION_3;
		@@ -289,21 +300,23 @@ static void SetInheritable(JNIEnv* env, uint64_t inheritable) {

		__user_cap_data_struct capdata[2];
		if (capget(&capheader, &capdata[0]) == -1) {
		ALOGE("capget failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "capget failed");
		*error_msg = CREATE_ERROR("capget failed: %s", strerror(errno));
		return false;
		}

		capdata[0].inheritable = inheritable;
		capdata[1].inheritable = inheritable >> 32;

		if (capset(&capheader, &capdata[0]) == -1) {
		ALOGE("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno));
		RuntimeAbort(env, __LINE__, "capset failed");
		*error_msg = CREATE_ERROR("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno));
		return false;
		}

		return true;
		}

		static void SetCapabilities(JNIEnv* env, uint64_t permitted, uint64_t effective,
		uint64_t inheritable) {
		static bool SetCapabilities(uint64_t permitted, uint64_t effective, uint64_t inheritable,
		std::string* error_msg) {
		__user_cap_header_struct capheader;
		memset(&capheader, 0, sizeof(capheader));
		capheader.version = _LINUX_CAPABILITY_VERSION_3;
		@@ -319,18 +332,20 @@ static void SetCapabilities(JNIEnv* env, uint64_t permitted, uint64_t effective,
		capdata[1].inheritable = inheritable >> 32;

		if (capset(&capheader, &capdata[0]) == -1) {
		ALOGE("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") failed: %s", permitted,
		effective, inheritable, strerror(errno));
		RuntimeAbort(env, __LINE__, "capset failed");
		*error_msg = CREATE_ERROR("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") "
		"failed: %s", permitted, effective, inheritable, strerror(errno));
		return false;
		}
		return true;
		}

		static void SetSchedulerPolicy(JNIEnv* env) {
		static bool SetSchedulerPolicy(std::string* error_msg) {
		errno = -set_sched_policy(0, SP_DEFAULT);
		if (errno != 0) {
		ALOGE("set_sched_policy(0, SP_DEFAULT) failed");
		RuntimeAbort(env, __LINE__, "set_sched_policy(0, SP_DEFAULT) failed");
		*error_msg = CREATE_ERROR("set_sched_policy(0, SP_DEFAULT) failed: %s", strerror(errno));
		return false;
		}
		return true;
		}

		static int UnmountTree(const char* path) {
		@@ -364,7 +379,7 @@ static int UnmountTree(const char* path) {
		// Create a private mount namespace and bind mount appropriate emulated
		// storage for the given user.
		static bool MountEmulatedStorage(uid_t uid, jint mount_mode,
		bool force_mount_namespace) {
		bool force_mount_namespace, std::string* error_msg) {
		// See storage config details at http://source.android.com/tech/storage/

		String8 storageSource;
		@@ -381,7 +396,7 @@ static bool MountEmulatedStorage(uid_t uid, jint mount_mode,

		// Create a second private mount namespace for our process
		if (unshare(CLONE_NEWNS) == -1) {
		ALOGW("Failed to unshare(): %s", strerror(errno));
		*error_msg = CREATE_ERROR("Failed to unshare(): %s", strerror(errno));
		return false;
		}

		@@ -392,7 +407,9 @@ static bool MountEmulatedStorage(uid_t uid, jint mount_mode,

		if (TEMP_FAILURE_RETRY(mount(storageSource.string(), "/storage",
		NULL, MS_BIND \| MS_REC \| MS_SLAVE, NULL)) == -1) {
		ALOGW("Failed to mount %s to /storage: %s", storageSource.string(), strerror(errno));
		*error_msg = CREATE_ERROR("Failed to mount %s to /storage: %s",
		storageSource.string(),
		strerror(errno));
		return false;
		}

		@@ -400,11 +417,14 @@ static bool MountEmulatedStorage(uid_t uid, jint mount_mode,
		userid_t user_id = multiuser_get_user_id(uid);
		const String8 userSource(String8::format("/mnt/user/%d", user_id));
		if (fs_prepare_dir(userSource.string(), 0751, 0, 0) == -1) {
		*error_msg = CREATE_ERROR("fs_prepare_dir failed on %s", userSource.string());
		return false;
		}
		if (TEMP_FAILURE_RETRY(mount(userSource.string(), "/storage/self",
		NULL, MS_BIND, NULL)) == -1) {
		ALOGW("Failed to mount %s to /storage/self: %s", userSource.string(), strerror(errno));
		*error_msg = CREATE_ERROR("Failed to mount %s to /storage/self: %s",
		userSource.string(),
		strerror(errno));
		return false;
		}

		@@ -436,31 +456,32 @@ static bool NeedsNoRandomizeWorkaround() {
		// descriptor (if any) is closed via dup2(), replacing it with a valid
		// (open) descriptor to /dev/null.

		static void DetachDescriptors(JNIEnv* env, jintArray fdsToClose) {
		static bool DetachDescriptors(JNIEnv* env, jintArray fdsToClose, std::string* error_msg) {
		if (!fdsToClose) {
		return;
		return true;
		}
		jsize count = env->GetArrayLength(fdsToClose);
		ScopedIntArrayRO ar(env, fdsToClose);
		if (ar.get() == NULL) {
		RuntimeAbort(env, __LINE__, "Bad fd array");
		*error_msg = "Bad fd array";
		return false;
		}
		jsize i;
		int devnull;
		for (i = 0; i < count; i++) {
		devnull = open("/dev/null", O_RDWR);
		if (devnull < 0) {
		ALOGE("Failed to open /dev/null: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Failed to open /dev/null");
		continue;
		*error_msg = std::string("Failed to open /dev/null: ").append(strerror(errno));
		return false;
		}
		ALOGV("Switching descriptor %d to /dev/null: %s", ar[i], strerror(errno));
		if (dup2(devnull, ar[i]) < 0) {
		ALOGE("Failed dup2() on descriptor %d: %s", ar[i], strerror(errno));
		RuntimeAbort(env, __LINE__, "Failed dup2()");
		*error_msg = StringPrintf("Failed dup2() on descriptor %d: %s", ar[i], strerror(errno));
		return false;
		}
		close(devnull);
		}
		return true;
		}

		void SetThreadName(const char* thread_name) {
		@@ -495,20 +516,23 @@ void SetThreadName(const char* thread_name) {
		// The list of open zygote file descriptors.
		static FileDescriptorTable* gOpenFdTable = NULL;

		static void FillFileDescriptorVector(JNIEnv* env,
		static bool FillFileDescriptorVector(JNIEnv* env,
		jintArray java_fds,
		std::vector<int>* fds) {
		std::vector<int>* fds,
		std::string* error_msg) {
		CHECK(fds != nullptr);
		if (java_fds != nullptr) {
		ScopedIntArrayRO ar(env, java_fds);
		if (ar.get() == nullptr) {
		RuntimeAbort(env, __LINE__, "Bad fd array");
		*error_msg = "Bad fd array";
		return false;
		}
		fds->reserve(ar.size());
		for (size_t i = 0; i < ar.size(); ++i) {
		fds->push_back(ar[i]);
		}
		}
		return true;
		}

		// Utility routine to fork zygote and specialize the child process.
		@@ -526,32 +550,53 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		sigemptyset(&sigchld);
		sigaddset(&sigchld, SIGCHLD);

		auto fail_fn = [env, java_se_name, is_system_server](const std::string& msg)
		__attribute__ ((noreturn)) {
		const char* se_name_c_str = nullptr;
		std::unique_ptr<ScopedUtfChars> se_name;
		if (java_se_name != nullptr) {
		se_name.reset(new ScopedUtfChars(env, java_se_name));
		se_name_c_str = se_name->c_str();
		}
		if (se_name_c_str == nullptr && is_system_server) {
		se_name_c_str = "system_server";
		}
		const std::string& error_msg = (se_name_c_str == nullptr)
		? msg
		: StringPrintf("(%s) %s", se_name_c_str, msg.c_str());
		env->FatalError(error_msg.c_str());
		__builtin_unreachable();
		};

		// Temporarily block SIGCHLD during forks. The SIGCHLD handler might
		// log, which would result in the logging FDs we close being reopened.
		// This would cause failures because the FDs are not whitelisted.
		//
		// Note that the zygote process is single threaded at this point.
		if (sigprocmask(SIG_BLOCK, &sigchld, nullptr) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_BLOCK, { SIGCHLD }) failed.");
		fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
		}

		// Close any logging related FDs before we start evaluating the list of
		// file descriptors.
		__android_log_close();

		std::string error_msg;

		// If this is the first fork for this zygote, create the open FD table.
		// If it isn't, we just need to check whether the list of open files has
		// changed (and it shouldn't in the normal case).
		std::vector<int> fds_to_ignore;
		FillFileDescriptorVector(env, fdsToIgnore, &fds_to_ignore);
		if (!FillFileDescriptorVector(env, fdsToIgnore, &fds_to_ignore, &error_msg)) {
		fail_fn(error_msg);
		}
		if (gOpenFdTable == NULL) {
		gOpenFdTable = FileDescriptorTable::Create(fds_to_ignore);
		gOpenFdTable = FileDescriptorTable::Create(fds_to_ignore, &error_msg);
		if (gOpenFdTable == NULL) {
		RuntimeAbort(env, __LINE__, "Unable to construct file descriptor table.");
		fail_fn(error_msg);
		}
		} else if (!gOpenFdTable->Restat(fds_to_ignore)) {
		RuntimeAbort(env, __LINE__, "Unable to restat file descriptor table.");
		} else if (!gOpenFdTable->Restat(fds_to_ignore, &error_msg)) {
		fail_fn(error_msg);
		}

		pid_t pid = fork();
		@@ -560,17 +605,18 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		PreApplicationInit();

		// Clean up any descriptors which must be closed immediately
		DetachDescriptors(env, fdsToClose);
		if (!DetachDescriptors(env, fdsToClose, &error_msg)) {
		fail_fn(error_msg);
		}

		// Re-open all remaining open file descriptors so that they aren't shared
		// with the zygote across a fork.
		if (!gOpenFdTable->ReopenOrDetach()) {
		RuntimeAbort(env, __LINE__, "Unable to reopen whitelisted descriptors.");
		if (!gOpenFdTable->ReopenOrDetach(&error_msg)) {
		fail_fn(error_msg);
		}

		if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed.");
		fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
		}

		// Must be called when the new process still has CAP_SYS_ADMIN. The other alternative is to
		@@ -580,11 +626,17 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra

		// Keep capabilities across UID change, unless we're staying root.
		if (uid != 0) {
		EnableKeepCapabilities(env);
		if (!EnableKeepCapabilities(&error_msg)) {
		fail_fn(error_msg);
		}
		}

		SetInheritable(env, permittedCapabilities);
		DropCapabilitiesBoundingSet(env);
		if (!SetInheritable(permittedCapabilities, &error_msg)) {
		fail_fn(error_msg);
		}
		if (!DropCapabilitiesBoundingSet(&error_msg)) {
		fail_fn(error_msg);
		}

		bool use_native_bridge = !is_system_server && (instructionSet != NULL)
		&& android::NativeBridgeAvailable();
		@@ -601,8 +653,8 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		ALOGW("Native bridge will not be used because dataDir == NULL.");
		}

		if (!MountEmulatedStorage(uid, mount_external, use_native_bridge)) {
		ALOGW("Failed to mount emulated storage: %s", strerror(errno));
		if (!MountEmulatedStorage(uid, mount_external, use_native_bridge, &error_msg)) {
		ALOGW("Failed to mount emulated storage: %s (%s)", error_msg.c_str(), strerror(errno));
		if (errno == ENOTCONN \|\| errno == EROFS) {
		// When device is actively encrypting, we get ENOTCONN here
		// since FUSE was mounted before the framework restarted.
		@@ -610,7 +662,7 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		// FUSE hasn't been created yet by init.
		// In either case, continue without external storage.
		} else {
		RuntimeAbort(env, __LINE__, "Cannot continue without emulated storage");
		fail_fn(error_msg);
		}
		}

		@@ -625,9 +677,14 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		}
		}

		SetGids(env, javaGids);
		std::string error_msg;
		if (!SetGids(env, javaGids, &error_msg)) {
		fail_fn(error_msg);
		}

		SetRLimits(env, javaRlimits);
		if (!SetRLimits(env, javaRlimits, &error_msg)) {
		fail_fn(error_msg);
		}

		if (use_native_bridge) {
		ScopedUtfChars isa_string(env, instructionSet);
		@@ -637,14 +694,12 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra

		int rc = setresgid(gid, gid, gid);
		if (rc == -1) {
		ALOGE("setresgid(%d) failed: %s", gid, strerror(errno));
		RuntimeAbort(env, __LINE__, "setresgid failed");
		fail_fn(CREATE_ERROR("setresgid(%d) failed: %s", gid, strerror(errno)));
		}

		rc = setresuid(uid, uid, uid);
		if (rc == -1) {
		ALOGE("setresuid(%d) failed: %s", uid, strerror(errno));
		RuntimeAbort(env, __LINE__, "setresuid failed");
		fail_fn(CREATE_ERROR("setresuid(%d) failed: %s", uid, strerror(errno)));
		}

		if (NeedsNoRandomizeWorkaround()) {
		@@ -656,9 +711,14 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		}
		}

		SetCapabilities(env, permittedCapabilities, effectiveCapabilities, permittedCapabilities);
		if (!SetCapabilities(permittedCapabilities, effectiveCapabilities, permittedCapabilities,
		&error_msg)) {
		fail_fn(error_msg);
		}

		SetSchedulerPolicy(env);
		if (!SetSchedulerPolicy(&error_msg)) {
		fail_fn(error_msg);
		}

		const char* se_info_c_str = NULL;
		ScopedUtfChars* se_info = NULL;
		@@ -666,7 +726,7 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		se_info = new ScopedUtfChars(env, java_se_info);
		se_info_c_str = se_info->c_str();
		if (se_info_c_str == NULL) {
		RuntimeAbort(env, __LINE__, "se_info_c_str == NULL");
		fail_fn("se_info_c_str == NULL");
		}
		}
		const char* se_name_c_str = NULL;
		@@ -675,14 +735,13 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		se_name = new ScopedUtfChars(env, java_se_name);
		se_name_c_str = se_name->c_str();
		if (se_name_c_str == NULL) {
		RuntimeAbort(env, __LINE__, "se_name_c_str == NULL");
		fail_fn("se_name_c_str == NULL");
		}
		}
		rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str);
		if (rc == -1) {
		ALOGE("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed", uid,
		is_system_server, se_info_c_str, se_name_c_str);
		RuntimeAbort(env, __LINE__, "selinux_android_setcontext failed");
		fail_fn(CREATE_ERROR("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed", uid,
		is_system_server, se_info_c_str, se_name_c_str));
		}

		// Make it easier to debug audit logs by setting the main thread's name to the
		@@ -703,15 +762,14 @@ static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArra
		env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, runtime_flags,
		is_system_server, is_child_zygote, instructionSet);
		if (env->ExceptionCheck()) {
		RuntimeAbort(env, __LINE__, "Error calling post fork hooks.");
		fail_fn("Error calling post fork hooks.");
		}
		} else if (pid > 0) {
		// the parent process

		// We blocked SIGCHLD prior to a fork, we unblock it here.
		if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) {
		ALOGE("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno));
		RuntimeAbort(env, __LINE__, "Call to sigprocmask(SIG_UNBLOCK, { SIGCHLD }) failed.");
		fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
		}
		}
		return pid;

core/jni/fd_utils.cpp

+122 −43

File changed.

Preview size limit exceeded, changes collapsed.

core/jni/fd_utils.h

+7 −47

Original line number	Diff line number	Diff line
		@@ -28,6 +28,8 @@

		#include <android-base/macros.h>

		class FileDescriptorInfo;

		// Whitelist of open paths that the zygote is allowed to keep open.
		//
		// In addition to the paths listed in kPathWhitelist in file_utils.cpp, and
		@@ -66,49 +68,6 @@ class FileDescriptorWhitelist {
		DISALLOW_COPY_AND_ASSIGN(FileDescriptorWhitelist);
		};

		// Keeps track of all relevant information (flags, offset etc.) of an
		// open zygote file descriptor.
		class FileDescriptorInfo {
		public:
		// Create a FileDescriptorInfo for a given file descriptor. Returns
		// \|NULL\| if an error occurred.
		static FileDescriptorInfo* CreateFromFd(int fd);

		// Checks whether the file descriptor associated with this object
		// refers to the same description.
		bool Restat() const;

		bool ReopenOrDetach() const;

		const int fd;
		const struct stat stat;
		const std::string file_path;
		const int open_flags;
		const int fd_flags;
		const int fs_flags;
		const off_t offset;
		const bool is_sock;

		private:
		FileDescriptorInfo(int fd);

		FileDescriptorInfo(struct stat stat, const std::string& file_path, int fd, int open_flags,
		int fd_flags, int fs_flags, off_t offset);

		// Returns the locally-bound name of the socket \|fd\|. Returns true
		// iff. all of the following hold :
		//
		// - the socket's sa_family is AF_UNIX.
		// - the length of the path is greater than zero (i.e, not an unnamed socket).
		// - the first byte of the path isn't zero (i.e, not a socket with an abstract
		// address).
		static bool GetSocketName(const int fd, std::string* result);

		bool DetachSocket() const;

		DISALLOW_COPY_AND_ASSIGN(FileDescriptorInfo);
		};

		// A FileDescriptorTable is a collection of FileDescriptorInfo objects
		// keyed by their FDs.
		class FileDescriptorTable {
		@@ -116,19 +75,20 @@ class FileDescriptorTable {
		// Creates a new FileDescriptorTable. This function scans
		// /proc/self/fd for the list of open file descriptors and collects
		// information about them. Returns NULL if an error occurs.
		static FileDescriptorTable* Create(const std::vector<int>& fds_to_ignore);
		static FileDescriptorTable* Create(const std::vector<int>& fds_to_ignore,
		std::string* error_msg);

		bool Restat(const std::vector<int>& fds_to_ignore);
		bool Restat(const std::vector<int>& fds_to_ignore, std::string* error_msg);

		// Reopens all file descriptors that are contained in the table. Returns true
		// if all descriptors were successfully re-opened or detached, and false if an
		// error occurred.
		bool ReopenOrDetach();
		bool ReopenOrDetach(std::string* error_msg);

		private:
		FileDescriptorTable(const std::unordered_map<int, FileDescriptorInfo*>& map);

		bool RestatInternal(std::set<int>& open_fds);
		bool RestatInternal(std::set<int>& open_fds, std::string* error_msg);

		static int ParseFd(dirent* e, int dir_fd);