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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 "tools/cygprofile/lightweight_cygprofile.h"
#include <atomic>
#include <cstdio>
#include <cstring>
#include <string>
#include <vector>
#include "base/android/library_loader/anchor_functions.h"
#include "base/files/file.h"
#include "base/format_macros.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/strings/stringprintf.h"
#include "build/build_config.h"
#if !defined(ARCH_CPU_ARMEL)
#error Only supported on ARM.
#endif // !defined(ARCH_CPU_ARMEL)
// Must be applied to all functions within this file.
#define NO_INSTRUMENT_FUNCTION __attribute__((no_instrument_function))
namespace cygprofile {
namespace {
// 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;
// |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)) {
Disable();
// If the start and end addresses are set incorrectly, this code path is
// likely happening during a static initializer. Logging at this time is
// prone 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();
}
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 void 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;
}
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);
file.WriteAtCurrentPos(offset_str.c_str(),
static_cast<int>(offset_str.size()));
}
}
// Stops recording, and outputs the data to |path|.
NO_INSTRUMENT_FUNCTION void StopAndDumpToFile(int pid,
uint64_t start_ns_since_epoch) {
Disable();
for (int phase = 0; phase < kPhases; phase++) {
auto path = base::StringPrintf(
"/data/local/tmp/chrome/cyglog/"
"cygprofile-instrumented-code-hitmap-%d-%" PRIu64 ".txt_%d",
pid, start_ns_since_epoch, phase);
DumpToFile(base::FilePath(path), g_data[phase]);
}
}
} // namespace
NO_INSTRUMENT_FUNCTION void Disable() {
g_data_index.store(kPhases, std::memory_order_relaxed);
std::atomic_thread_fence(std::memory_order_seq_cst);
}
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 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);
}
}
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 cygprofile
extern "C" {
NO_INSTRUMENT_FUNCTION void __cyg_profile_func_enter_bare() {
cygprofile::RecordAddress<false>(
reinterpret_cast<size_t>(__builtin_return_address(0)));
}
} // extern "C"
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