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/*
* Copyright (C) 2019 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <inttypes.h>
#include <stdint.h>
#include <array>
#include <mutex>
#include <vector>
#include <android/fdsan.h>
#include <bionic/fdtrack.h>
#include <android-base/no_destructor.h>
#include <android-base/thread_annotations.h>
#include <async_safe/log.h>
#include <bionic/reserved_signals.h>
#include <unwindstack/LocalUnwinder.h>
struct FdEntry {
std::mutex mutex;
std::vector<unwindstack::LocalFrameData> backtrace GUARDED_BY(mutex);
};
extern "C" void fdtrack_dump();
using fdtrack_callback_t = bool (*)(int fd, const char* const* function_names,
const uint64_t* function_offsets, size_t count, void* arg);
extern "C" void fdtrack_iterate(fdtrack_callback_t callback, void* arg);
static void fd_hook(android_fdtrack_event* event);
// Backtraces for the first 4k file descriptors ought to be enough to diagnose an fd leak.
static constexpr size_t kFdTableSize = 4096;
// 32 frames, plus two to skip from fdtrack itself.
static constexpr size_t kStackDepth = 34;
static constexpr size_t kStackFrameSkip = 2;
static bool installed = false;
static std::array<FdEntry, kFdTableSize> stack_traces [[clang::no_destroy]];
static unwindstack::LocalUnwinder& Unwinder() {
static android::base::NoDestructor<unwindstack::LocalUnwinder> unwinder;
return *unwinder.get();
}
__attribute__((constructor)) static void ctor() {
for (auto& entry : stack_traces) {
entry.backtrace.reserve(kStackDepth);
}
signal(BIONIC_SIGNAL_FDTRACK, [](int) { fdtrack_dump(); });
if (Unwinder().Init()) {
android_fdtrack_hook_t expected = nullptr;
installed = android_fdtrack_compare_exchange_hook(&expected, &fd_hook);
}
}
__attribute__((destructor)) static void dtor() {
if (installed) {
android_fdtrack_hook_t expected = &fd_hook;
android_fdtrack_compare_exchange_hook(&expected, nullptr);
}
}
FdEntry* GetFdEntry(int fd) {
if (fd >= 0 && fd < static_cast<int>(kFdTableSize)) {
return &stack_traces[fd];
}
return nullptr;
}
static void fd_hook(android_fdtrack_event* event) {
if (event->type == ANDROID_FDTRACK_EVENT_TYPE_CREATE) {
if (FdEntry* entry = GetFdEntry(event->fd); entry) {
std::lock_guard<std::mutex> lock(entry->mutex);
entry->backtrace.clear();
Unwinder().Unwind(&entry->backtrace, kStackDepth);
}
} else if (event->type == ANDROID_FDTRACK_EVENT_TYPE_CLOSE) {
if (FdEntry* entry = GetFdEntry(event->fd); entry) {
std::lock_guard<std::mutex> lock(entry->mutex);
entry->backtrace.clear();
}
}
}
void fdtrack_iterate(fdtrack_callback_t callback, void* arg) {
bool prev = android_fdtrack_set_enabled(false);
for (int fd = 0; fd < static_cast<int>(stack_traces.size()); ++fd) {
const char* function_names[kStackDepth];
uint64_t function_offsets[kStackDepth];
FdEntry* entry = GetFdEntry(fd);
if (!entry) {
continue;
}
if (!entry->mutex.try_lock()) {
async_safe_format_log(ANDROID_LOG_WARN, "fdtrack", "fd %d locked, skipping", fd);
continue;
}
if (entry->backtrace.empty()) {
entry->mutex.unlock();
continue;
} else if (entry->backtrace.size() < 2) {
async_safe_format_log(ANDROID_LOG_WARN, "fdtrack", "fd %d missing frames: size = %zu", fd,
entry->backtrace.size());
entry->mutex.unlock();
continue;
}
for (size_t i = kStackFrameSkip; i < entry->backtrace.size(); ++i) {
size_t j = i - kStackFrameSkip;
function_names[j] = entry->backtrace[i].function_name.c_str();
function_offsets[j] = entry->backtrace[i].function_offset;
}
bool should_continue = callback(fd, function_names, function_offsets,
entry->backtrace.size() - kStackFrameSkip, arg);
entry->mutex.unlock();
if (!should_continue) {
break;
}
}
android_fdtrack_set_enabled(prev);
}
void fdtrack_dump() {
if (!installed) {
async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fdtrack not installed");
} else {
async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fdtrack dumping...");
}
fdtrack_iterate(
[](int fd, const char* const* function_names, const uint64_t* function_offsets, size_t count,
void*) {
uint64_t fdsan_owner = android_fdsan_get_owner_tag(fd);
if (fdsan_owner != 0) {
async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fd %d: (owner = 0x%" PRIx64 ")", fd,
fdsan_owner);
} else {
async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", "fd %d: (unowned)", fd);
}
for (size_t i = 0; i < count; ++i) {
async_safe_format_log(ANDROID_LOG_INFO, "fdtrack", " %zu: %s+%" PRIu64, i,
function_names[i], function_offsets[i]);
}
return true;
},
nullptr);
}
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