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//===-- xray_inmemory_log.cc ------------------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of XRay, a dynamic runtime instrumentation system.
//
// Implementation of a simple in-memory log of XRay events. This defines a
// logging function that's compatible with the XRay handler interface, and
// routines for exporting data to files.
//
//===----------------------------------------------------------------------===//
#include <cassert>
#include <fcntl.h>
#include <mutex>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <thread>
#include <unistd.h>
#include "sanitizer_common/sanitizer_libc.h"
#include "xray/xray_records.h"
#include "xray_defs.h"
#include "xray_flags.h"
#include "xray_interface_internal.h"
#include "xray_tsc.h"
#include "xray_utils.h"
// __xray_InMemoryRawLog will use a thread-local aligned buffer capped to a
// certain size (32kb by default) and use it as if it were a circular buffer for
// events. We store simple fixed-sized entries in the log for external analysis.
extern "C" {
void __xray_InMemoryRawLog(int32_t FuncId,
XRayEntryType Type) XRAY_NEVER_INSTRUMENT;
}
namespace __xray {
std::mutex LogMutex;
class ThreadExitFlusher {
int Fd;
XRayRecord *Start;
size_t &Offset;
public:
explicit ThreadExitFlusher(int Fd, XRayRecord *Start,
size_t &Offset) XRAY_NEVER_INSTRUMENT
: Fd(Fd),
Start(Start),
Offset(Offset) {}
~ThreadExitFlusher() XRAY_NEVER_INSTRUMENT {
std::lock_guard<std::mutex> L(LogMutex);
if (Fd > 0 && Start != nullptr) {
retryingWriteAll(Fd, reinterpret_cast<char *>(Start),
reinterpret_cast<char *>(Start + Offset));
// Because this thread's exit could be the last one trying to write to the
// file and that we're not able to close out the file properly, we sync
// instead and hope that the pending writes are flushed as the thread
// exits.
fsync(Fd);
}
}
};
} // namespace __xray
using namespace __xray;
static int __xray_OpenLogFile() XRAY_NEVER_INSTRUMENT {
int F = getLogFD();
if (F == -1)
return -1;
// Test for required CPU features and cache the cycle frequency
static bool TSCSupported = probeRequiredCPUFeatures();
static uint64_t CycleFrequency = TSCSupported ? getTSCFrequency()
: __xray::NanosecondsPerSecond;
// Since we're here, we get to write the header. We set it up so that the
// header will only be written once, at the start, and let the threads
// logging do writes which just append.
XRayFileHeader Header;
Header.Version = 1;
Header.Type = FileTypes::NAIVE_LOG;
Header.CycleFrequency = CycleFrequency;
// FIXME: Actually check whether we have 'constant_tsc' and 'nonstop_tsc'
// before setting the values in the header.
Header.ConstantTSC = 1;
Header.NonstopTSC = 1;
retryingWriteAll(F, reinterpret_cast<char *>(&Header),
reinterpret_cast<char *>(&Header) + sizeof(Header));
return F;
}
template <class RDTSC>
void __xray_InMemoryRawLog(int32_t FuncId, XRayEntryType Type,
RDTSC ReadTSC) XRAY_NEVER_INSTRUMENT {
using Buffer =
std::aligned_storage<sizeof(XRayRecord), alignof(XRayRecord)>::type;
static constexpr size_t BuffLen = 1024;
thread_local static Buffer InMemoryBuffer[BuffLen] = {};
thread_local static size_t Offset = 0;
static int Fd = __xray_OpenLogFile();
if (Fd == -1)
return;
thread_local __xray::ThreadExitFlusher Flusher(
Fd, reinterpret_cast<__xray::XRayRecord *>(InMemoryBuffer), Offset);
thread_local pid_t TId = syscall(SYS_gettid);
// First we get the useful data, and stuff it into the already aligned buffer
// through a pointer offset.
auto &R = reinterpret_cast<__xray::XRayRecord *>(InMemoryBuffer)[Offset];
R.RecordType = RecordTypes::NORMAL;
R.TSC = ReadTSC(R.CPU);
R.TId = TId;
R.Type = Type;
R.FuncId = FuncId;
++Offset;
if (Offset == BuffLen) {
std::lock_guard<std::mutex> L(LogMutex);
auto RecordBuffer = reinterpret_cast<__xray::XRayRecord *>(InMemoryBuffer);
retryingWriteAll(Fd, reinterpret_cast<char *>(RecordBuffer),
reinterpret_cast<char *>(RecordBuffer + Offset));
Offset = 0;
}
}
void __xray_InMemoryRawLogRealTSC(int32_t FuncId,
XRayEntryType Type) XRAY_NEVER_INSTRUMENT {
__xray_InMemoryRawLog(FuncId, Type, __xray::readTSC);
}
void __xray_InMemoryEmulateTSC(int32_t FuncId,
XRayEntryType Type) XRAY_NEVER_INSTRUMENT {
__xray_InMemoryRawLog(FuncId, Type, [](uint8_t &CPU) XRAY_NEVER_INSTRUMENT {
timespec TS;
int result = clock_gettime(CLOCK_REALTIME, &TS);
if (result != 0) {
Report("clock_gettimg(2) return %d, errno=%d.", result, int(errno));
TS = {0, 0};
}
CPU = 0;
return TS.tv_sec * __xray::NanosecondsPerSecond + TS.tv_nsec;
});
}
static auto UNUSED Unused = [] {
auto UseRealTSC = probeRequiredCPUFeatures();
if (!UseRealTSC)
Report("WARNING: Required CPU features missing for XRay instrumentation, "
"using emulation instead.\n");
if (flags()->xray_naive_log)
__xray_set_handler(UseRealTSC ? __xray_InMemoryRawLogRealTSC
: __xray_InMemoryEmulateTSC);
return true;
}();
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