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- // Copyright (c) 2017 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #include "base/android/orderfile/orderfile_instrumentation.h"
- #include <time.h>
- #include <unistd.h>
- #include <atomic>
- #include <cstdio>
- #include <cstring>
- #include <sstream>
- #include <string>
- #include <thread>
- #include <vector>
- #include "base/android/library_loader/anchor_functions.h"
- #include "base/android/orderfile/orderfile_buildflags.h"
- #include "base/files/file.h"
- #include "base/format_macros.h"
- #include "base/logging.h"
- #include "base/strings/stringprintf.h"
- #include "build/build_config.h"
- #if BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- #include <sstream>
- #include "base/command_line.h"
- #include "base/time/time.h"
- #include "base/trace_event/memory_dump_manager.h" // no-presubmit-check
- #include "base/trace_event/memory_dump_provider.h" // no-presubmit-check
- #endif // BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- #if !BUILDFLAG(SUPPORTS_CODE_ORDERING)
- #error Requires code ordering support (arm/arm64/x86/x86_64).
- #endif // !BUILDFLAG(SUPPORTS_CODE_ORDERING)
- // Must be applied to all functions within this file.
- #define NO_INSTRUMENT_FUNCTION __attribute__((no_instrument_function))
- namespace base {
- namespace android {
- namespace orderfile {
- namespace {
- // Constants used for StartDelayedDump().
- constexpr int kDelayInSeconds = 30;
- constexpr int kInitialDelayInSeconds = kPhases == 1 ? kDelayInSeconds : 5;
- #if BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- // This is defined in content/public/common/content_switches.h, which is not
- // accessible in ::base.
- constexpr const char kProcessTypeSwitch[] = "type";
- #endif // BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- // These are large overestimates, which is not an issue, as the data is
- // allocated in .bss, and on linux doesn't take any actual memory when it's not
- // touched.
- constexpr size_t kBitfieldSize = 1 << 22;
- constexpr size_t kMaxTextSizeInBytes = kBitfieldSize * (4 * 32);
- constexpr size_t kMaxElements = 1 << 20;
- // Data required to log reached offsets.
- struct LogData {
- std::atomic<uint32_t> offsets[kBitfieldSize];
- std::atomic<size_t> ordered_offsets[kMaxElements];
- std::atomic<size_t> index;
- };
- LogData g_data[kPhases];
- std::atomic<int> g_data_index;
- // Number of unexpected addresses, that is addresses that are not within [start,
- // end) bounds for the executable code.
- //
- // This should be exactly 0, since the start and end of .text should be known
- // perfectly by the linker, but it does happen. See crbug.com/1186598.
- std::atomic<int> g_unexpected_addresses;
- #if BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- // Dump offsets when a memory dump is requested. Used only if
- // switches::kDevtoolsInstrumentationDumping is set.
- class OrderfileMemoryDumpHook : public base::trace_event::MemoryDumpProvider {
- NO_INSTRUMENT_FUNCTION bool OnMemoryDump(
- const base::trace_event::MemoryDumpArgs& args,
- base::trace_event::ProcessMemoryDump* pmd) override {
- // Disable instrumentation now to cut down on orderfile pollution.
- if (!Disable()) {
- return true; // A dump has already been started.
- }
- std::stringstream process_type_str;
- Dump(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
- kProcessTypeSwitch));
- return true; // If something goes awry, a fatal error will be created
- // internally.
- }
- };
- #endif // BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- // |RecordAddress()| adds an element to a concurrent bitset and to a concurrent
- // append-only list of offsets.
- //
- // Ordering:
- // Two consecutive calls to |RecordAddress()| from the same thread will be
- // ordered in the same way in the result, as written by
- // |StopAndDumpToFile()|. The result will contain exactly one instance of each
- // unique offset relative to |kStartOfText| passed to |RecordAddress()|.
- //
- // Implementation:
- // The "set" part is implemented with a bitfield, |g_offset|. The insertion
- // order is recorded in |g_ordered_offsets|.
- // This is not a class to make sure there isn't a static constructor, as it
- // would cause issue with an instrumented static constructor calling this code.
- //
- // Limitations:
- // - Only records offsets to addresses between |kStartOfText| and |kEndOfText|.
- // - Capacity of the set is limited by |kMaxElements|.
- // - Some insertions at the end of collection may be lost.
- // Records that |address| has been reached, if recording is enabled.
- // To avoid infinite recursion, this *must* *never* call any instrumented
- // function, unless |Disable()| is called first.
- template <bool for_testing>
- __attribute__((always_inline, no_instrument_function)) void RecordAddress(
- size_t address) {
- int index = g_data_index.load(std::memory_order_relaxed);
- if (index >= kPhases)
- return;
- const size_t start =
- for_testing ? kStartOfTextForTesting : base::android::kStartOfText;
- const size_t end =
- for_testing ? kEndOfTextForTesting : base::android::kEndOfText;
- if (UNLIKELY(address < start || address > end)) {
- if (!AreAnchorsSane()) {
- // Something is really wrong with the anchors, and this is likely to be
- // triggered from within a static constructor, where logging is likely to
- // deadlock. By crashing immediately we at least have a chance to get a
- // stack trace from the system to give some clue about the nature of the
- // problem.
- IMMEDIATE_CRASH();
- }
- // We should really crash at the first instance, but it does happen on bots,
- // for a mysterious reason. Give it some leeway. Note that since we don't
- // remember the caller address, if a single function is misplaced but we get
- // many calls to it, then we still crash. If this is the case, add
- // deduplication.
- //
- // Bumped to 100 temporarily as part of crbug.com/1265928 investigation.
- if (g_unexpected_addresses.fetch_add(1, std::memory_order_relaxed) < 100) {
- return;
- }
- Disable();
- LOG(FATAL) << "Too many unexpected addresses! start = " << std::hex << start
- << " end = " << end << " address = " << address;
- }
- size_t offset = address - start;
- static_assert(sizeof(int) == 4,
- "Collection and processing code assumes that sizeof(int) == 4");
- size_t offset_index = offset / 4;
- auto* offsets = g_data[index].offsets;
- // Atomically set the corresponding bit in the array.
- std::atomic<uint32_t>* element = offsets + (offset_index / 32);
- // First, a racy check. This saves a CAS if the bit is already set, and
- // allows the cache line to remain shared acoss CPUs in this case.
- uint32_t value = element->load(std::memory_order_relaxed);
- uint32_t mask = 1 << (offset_index % 32);
- if (value & mask)
- return;
- auto before = element->fetch_or(mask, std::memory_order_relaxed);
- if (before & mask)
- return;
- // We were the first one to set the element, record it in the ordered
- // elements list.
- // Use relaxed ordering, as the value is not published, or used for
- // synchronization.
- auto* ordered_offsets = g_data[index].ordered_offsets;
- auto& ordered_offsets_index = g_data[index].index;
- size_t insertion_index =
- ordered_offsets_index.fetch_add(1, std::memory_order_relaxed);
- if (UNLIKELY(insertion_index >= kMaxElements)) {
- Disable();
- LOG(FATAL) << "Too many reached offsets";
- }
- ordered_offsets[insertion_index].store(offset, std::memory_order_relaxed);
- }
- NO_INSTRUMENT_FUNCTION bool DumpToFile(const base::FilePath& path,
- const LogData& data) {
- auto file =
- base::File(path, base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE);
- if (!file.IsValid()) {
- PLOG(ERROR) << "Could not open " << path;
- return false;
- }
- if (data.index == 0) {
- LOG(ERROR) << "No entries to dump";
- return false;
- }
- size_t count = data.index - 1;
- for (size_t i = 0; i < count; i++) {
- // |g_ordered_offsets| is initialized to 0, so a 0 in the middle of it
- // indicates a case where the index was incremented, but the write is not
- // visible in this thread yet. Safe to skip, also because the function at
- // the start of text is never called.
- auto offset = data.ordered_offsets[i].load(std::memory_order_relaxed);
- if (!offset)
- continue;
- auto offset_str = base::StringPrintf("%" PRIuS "\n", offset);
- if (file.WriteAtCurrentPos(offset_str.c_str(),
- static_cast<int>(offset_str.size())) < 0) {
- // If the file could be opened, but writing has failed, it's likely that
- // data was partially written. Producing incomplete profiling data would
- // lead to a poorly performing orderfile, but might not be otherwised
- // noticed. So we crash instead.
- LOG(FATAL) << "Error writing profile data";
- }
- }
- return true;
- }
- // Stops recording, and outputs the data to |path|.
- NO_INSTRUMENT_FUNCTION void StopAndDumpToFile(int pid,
- uint64_t start_ns_since_epoch,
- const std::string& tag) {
- Disable();
- for (int phase = 0; phase < kPhases; phase++) {
- std::string tag_str;
- if (!tag.empty())
- tag_str = base::StringPrintf("%s-", tag.c_str());
- auto path = base::StringPrintf(
- "/data/local/tmp/chrome/orderfile/profile-hitmap-%s%d-%" PRIu64
- ".txt_%d",
- tag_str.c_str(), pid, start_ns_since_epoch, phase);
- if (!DumpToFile(base::FilePath(path), g_data[phase])) {
- LOG(ERROR) << "Problem with dump " << phase << " (" << tag << ")";
- }
- }
- int unexpected_addresses =
- g_unexpected_addresses.load(std::memory_order_relaxed);
- if (unexpected_addresses != 0) {
- LOG(WARNING) << "Got " << unexpected_addresses << " unexpected addresses!";
- }
- }
- } // namespace
- // After a call to Disable(), any function can be called, as reentrancy into the
- // instrumentation function will be mitigated.
- NO_INSTRUMENT_FUNCTION bool Disable() {
- auto old_phase = g_data_index.exchange(kPhases, std::memory_order_relaxed);
- std::atomic_thread_fence(std::memory_order_seq_cst);
- return old_phase != kPhases;
- }
- NO_INSTRUMENT_FUNCTION void SanityChecks() {
- CHECK_LT(base::android::kEndOfText - base::android::kStartOfText,
- kMaxTextSizeInBytes);
- CHECK(base::android::IsOrderingSane());
- }
- NO_INSTRUMENT_FUNCTION bool SwitchToNextPhaseOrDump(
- int pid,
- uint64_t start_ns_since_epoch) {
- int before = g_data_index.fetch_add(1, std::memory_order_relaxed);
- if (before + 1 == kPhases) {
- StopAndDumpToFile(pid, start_ns_since_epoch, "");
- return true;
- }
- return false;
- }
- NO_INSTRUMENT_FUNCTION void StartDelayedDump() {
- // Using std::thread and not using base::TimeTicks() in order to to not call
- // too many base:: symbols that would pollute the reached symbol dumps.
- struct timespec ts;
- if (clock_gettime(CLOCK_MONOTONIC, &ts))
- PLOG(FATAL) << "clock_gettime.";
- uint64_t start_ns_since_epoch =
- static_cast<uint64_t>(ts.tv_sec) * 1000 * 1000 * 1000 + ts.tv_nsec;
- int pid = getpid();
- #if BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- static auto* g_orderfile_memory_dump_hook = new OrderfileMemoryDumpHook();
- base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
- g_orderfile_memory_dump_hook, "Orderfile", nullptr);
- #endif // BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- std::thread([pid, start_ns_since_epoch]() {
- sleep(kInitialDelayInSeconds);
- #if BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- SwitchToNextPhaseOrDump(pid, start_ns_since_epoch);
- // Return, letting devtools tracing handle any post-startup phases.
- #else
- while (!SwitchToNextPhaseOrDump(pid, start_ns_since_epoch))
- sleep(kDelayInSeconds);
- #endif // BUILDFLAG(DEVTOOLS_INSTRUMENTATION_DUMPING)
- })
- .detach();
- }
- NO_INSTRUMENT_FUNCTION void Dump(const std::string& tag) {
- // As profiling has been disabled, none of the uses of ::base symbols below
- // will enter the symbol dump.
- StopAndDumpToFile(
- getpid(), (base::Time::Now() - base::Time::UnixEpoch()).InNanoseconds(),
- tag);
- }
- NO_INSTRUMENT_FUNCTION void ResetForTesting() {
- Disable();
- g_data_index = 0;
- for (int i = 0; i < kPhases; i++) {
- memset(reinterpret_cast<uint32_t*>(g_data[i].offsets), 0,
- sizeof(uint32_t) * kBitfieldSize);
- memset(reinterpret_cast<uint32_t*>(g_data[i].ordered_offsets), 0,
- sizeof(uint32_t) * kMaxElements);
- g_data[i].index.store(0);
- }
- g_unexpected_addresses.store(0, std::memory_order_relaxed);
- }
- NO_INSTRUMENT_FUNCTION void RecordAddressForTesting(size_t address) {
- return RecordAddress<true>(address);
- }
- NO_INSTRUMENT_FUNCTION std::vector<size_t> GetOrderedOffsetsForTesting() {
- std::vector<size_t> result;
- size_t max_index = g_data[0].index.load(std::memory_order_relaxed);
- for (size_t i = 0; i < max_index; ++i) {
- auto value = g_data[0].ordered_offsets[i].load(std::memory_order_relaxed);
- if (value)
- result.push_back(value);
- }
- return result;
- }
- } // namespace orderfile
- } // namespace android
- } // namespace base
- extern "C" {
- NO_INSTRUMENT_FUNCTION void __cyg_profile_func_enter_bare() {
- base::android::orderfile::RecordAddress<false>(
- reinterpret_cast<size_t>(__builtin_return_address(0)));
- }
- } // extern "C"
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