263faa90e1
Trying to find a leak this year, it was very annoying that our traces were mostly filled with "junk" frames from the JNI implementation, making it quite a struggle to see what the actual calling code was... Bug: http://b/236197847 Test: treehugger Change-Id: I69e7d9b6432e1872e238168ebf3dc36feb7de7df
321 lines
11 KiB
C++
321 lines
11 KiB
C++
/*
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* Copyright (C) 2019 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <inttypes.h>
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#include <stdint.h>
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#include <array>
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#include <mutex>
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#include <string>
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#include <string_view>
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#include <thread>
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#include <utility>
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#include <vector>
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#include <android/fdsan.h>
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#include <android/set_abort_message.h>
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#include <bionic/fdtrack.h>
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#include <android-base/no_destructor.h>
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#include <android-base/thread_annotations.h>
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#include <async_safe/log.h>
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#include <bionic/reserved_signals.h>
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#include <unwindstack/Maps.h>
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#include <unwindstack/Regs.h>
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#include <unwindstack/RegsGetLocal.h>
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#include <unwindstack/Unwinder.h>
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struct FdEntry {
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std::mutex mutex;
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std::vector<unwindstack::FrameData> backtrace GUARDED_BY(mutex);
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};
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extern "C" void fdtrack_dump();
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extern "C" void fdtrack_dump_fatal();
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using fdtrack_callback_t = bool (*)(int fd, const char* const* function_names,
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const uint64_t* function_offsets, size_t count, void* arg);
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extern "C" void fdtrack_iterate(fdtrack_callback_t callback, void* arg);
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static void fd_hook(android_fdtrack_event* event);
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// Backtraces for the first 4k file descriptors ought to be enough to diagnose an fd leak.
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static constexpr size_t kFdTableSize = 4096;
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// Only unwind up to 32 frames outside of libfdtrack.so.
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static constexpr size_t kStackDepth = 32;
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// Skip any initial frames from libfdtrack.so.
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// Also ignore frames from ART (http://b/236197847) because we'd rather spend
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// our precious few frames on the actual Java calling code rather than the
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// implementation of JNI!
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static std::vector<std::string> kSkipFdtrackLib
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[[clang::no_destroy]] = {"libfdtrack.so", "libart.so"};
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static bool installed = false;
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static std::array<FdEntry, kFdTableSize> stack_traces [[clang::no_destroy]];
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static unwindstack::LocalUpdatableMaps& Maps() {
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static android::base::NoDestructor<unwindstack::LocalUpdatableMaps> maps;
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return *maps.get();
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}
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static std::shared_ptr<unwindstack::Memory>& ProcessMemory() {
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static android::base::NoDestructor<std::shared_ptr<unwindstack::Memory>> process_memory;
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return *process_memory.get();
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}
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__attribute__((constructor)) static void ctor() {
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for (auto& entry : stack_traces) {
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entry.backtrace.reserve(kStackDepth);
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}
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struct sigaction sa = {};
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sa.sa_sigaction = [](int, siginfo_t* siginfo, void*) {
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if (siginfo->si_code == SI_QUEUE && siginfo->si_int == 1) {
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fdtrack_dump_fatal();
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} else {
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fdtrack_dump();
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}
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};
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sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
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sigaction(BIONIC_SIGNAL_FDTRACK, &sa, nullptr);
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if (Maps().Parse()) {
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ProcessMemory() = unwindstack::Memory::CreateProcessMemoryThreadCached(getpid());
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android_fdtrack_hook_t expected = nullptr;
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installed = android_fdtrack_compare_exchange_hook(&expected, &fd_hook);
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}
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android_fdtrack_set_globally_enabled(true);
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}
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__attribute__((destructor)) static void dtor() {
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if (installed) {
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android_fdtrack_hook_t expected = &fd_hook;
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android_fdtrack_compare_exchange_hook(&expected, nullptr);
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}
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}
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FdEntry* GetFdEntry(int fd) {
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if (fd >= 0 && fd < static_cast<int>(kFdTableSize)) {
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return &stack_traces[fd];
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}
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return nullptr;
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}
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static void fd_hook(android_fdtrack_event* event) {
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if (event->type == ANDROID_FDTRACK_EVENT_TYPE_CREATE) {
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if (FdEntry* entry = GetFdEntry(event->fd); entry) {
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std::lock_guard<std::mutex> lock(entry->mutex);
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entry->backtrace.clear();
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std::unique_ptr<unwindstack::Regs> regs(unwindstack::Regs::CreateFromLocal());
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unwindstack::RegsGetLocal(regs.get());
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unwindstack::Unwinder unwinder(kStackDepth, &Maps(), regs.get(), ProcessMemory());
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unwinder.Unwind(&kSkipFdtrackLib);
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entry->backtrace = unwinder.ConsumeFrames();
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}
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} else if (event->type == ANDROID_FDTRACK_EVENT_TYPE_CLOSE) {
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if (FdEntry* entry = GetFdEntry(event->fd); entry) {
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std::lock_guard<std::mutex> lock(entry->mutex);
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entry->backtrace.clear();
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}
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}
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}
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void fdtrack_iterate(fdtrack_callback_t callback, void* arg) {
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bool prev = android_fdtrack_set_enabled(false);
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for (int fd = 0; fd < static_cast<int>(stack_traces.size()); ++fd) {
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const char* function_names[kStackDepth];
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uint64_t function_offsets[kStackDepth];
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FdEntry* entry = GetFdEntry(fd);
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if (!entry) {
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continue;
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}
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if (!entry->mutex.try_lock()) {
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async_safe_format_log(ANDROID_LOG_WARN, "fdtrack", "fd %d locked, skipping", fd);
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continue;
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}
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if (entry->backtrace.empty()) {
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entry->mutex.unlock();
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continue;
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} else if (entry->backtrace.size() < 2) {
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async_safe_format_log(ANDROID_LOG_WARN, "fdtrack", "fd %d missing frames: size = %zu", fd,
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entry->backtrace.size());
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entry->mutex.unlock();
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continue;
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}
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for (size_t i = 0; i < entry->backtrace.size(); ++i) {
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function_names[i] = entry->backtrace[i].function_name.c_str();
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function_offsets[i] = entry->backtrace[i].function_offset;
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}
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bool should_continue =
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callback(fd, function_names, function_offsets, entry->backtrace.size(), arg);
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entry->mutex.unlock();
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if (!should_continue) {
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break;
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}
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}
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android_fdtrack_set_enabled(prev);
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}
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static size_t hash_stack(const char* const* function_names, const uint64_t* function_offsets,
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size_t stack_depth) {
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size_t hash = 0;
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for (size_t i = 0; i < stack_depth; ++i) {
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// To future maintainers: if a libc++ update ever makes this invalid, replace this with +.
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hash = std::__hash_combine(hash, std::hash<std::string_view>()(function_names[i]));
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hash = std::__hash_combine(hash, std::hash<uint64_t>()(function_offsets[i]));
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}
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return hash;
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}
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static void fdtrack_dump_impl(bool fatal) {
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if (!installed) {
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async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fdtrack not installed");
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} else {
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async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fdtrack dumping...");
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}
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// If we're aborting, identify the most common stack in the hopes that it's the culprit,
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// and emit that in the abort message so crash reporting can separate different fd leaks out.
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// This is horrible and quadratic, but we need to avoid allocation since this can happen in
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// response to a signal generated asynchronously. We're only going to dump 1k fds by default,
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// and we're about to blow up the entire system, so this isn't too expensive.
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struct StackInfo {
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size_t hash = 0;
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size_t count = 0;
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size_t stack_depth = 0;
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const char* function_names[kStackDepth];
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uint64_t function_offsets[kStackDepth];
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};
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struct StackList {
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size_t count = 0;
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std::array<StackInfo, 128> data;
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};
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static StackList stacks;
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fdtrack_iterate(
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[](int fd, const char* const* function_names, const uint64_t* function_offsets,
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size_t stack_depth, void* stacks_ptr) {
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auto stacks = static_cast<StackList*>(stacks_ptr);
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uint64_t fdsan_owner = android_fdsan_get_owner_tag(fd);
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if (fdsan_owner != 0) {
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async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fd %d: (owner = 0x%" PRIx64 ")", fd,
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fdsan_owner);
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} else {
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async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fd %d: (unowned)", fd);
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}
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for (size_t i = 0; i < stack_depth; ++i) {
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async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", " %zu: %s+%" PRIu64, i,
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function_names[i], function_offsets[i]);
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}
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if (stacks) {
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size_t hash = hash_stack(function_names, function_offsets, stack_depth);
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bool found_stack = false;
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for (size_t i = 0; i < stacks->count; ++i) {
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if (stacks->data[i].hash == hash) {
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++stacks->data[i].count;
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found_stack = true;
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break;
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}
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}
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if (!found_stack) {
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if (stacks->count < stacks->data.size()) {
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auto& stack = stacks->data[stacks->count++];
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stack.hash = hash;
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stack.count = 1;
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stack.stack_depth = stack_depth;
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for (size_t i = 0; i < stack_depth; ++i) {
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stack.function_names[i] = function_names[i];
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stack.function_offsets[i] = function_offsets[i];
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}
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}
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}
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}
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return true;
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},
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fatal ? &stacks : nullptr);
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if (fatal) {
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// Find the most common stack.
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size_t max = 0;
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StackInfo* stack = nullptr;
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for (size_t i = 0; i < stacks.count; ++i) {
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if (stacks.data[i].count > max) {
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stack = &stacks.data[i];
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max = stack->count;
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}
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}
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static char buf[1024];
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if (!stack) {
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async_safe_format_buffer(buf, sizeof(buf),
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"aborting due to fd leak: failed to find most common stack");
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} else {
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char* p = buf;
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p += async_safe_format_buffer(buf, sizeof(buf),
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"aborting due to fd leak: most common stack =\n");
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for (size_t i = 0; i < stack->stack_depth; ++i) {
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ssize_t bytes_left = buf + sizeof(buf) - p;
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if (bytes_left > 0) {
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p += async_safe_format_buffer(p, buf + sizeof(buf) - p, " %zu: %s+%" PRIu64 "\n", i,
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stack->function_names[i], stack->function_offsets[i]);
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}
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}
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}
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android_set_abort_message(buf);
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// Abort on a different thread to avoid ART dumping runtime stacks.
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std::thread([]() { abort(); }).join();
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}
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}
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void fdtrack_dump() {
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fdtrack_dump_impl(false);
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}
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void fdtrack_dump_fatal() {
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fdtrack_dump_impl(true);
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}
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