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Diffstat (limited to 'lib/xray/xray_fdr_logging_impl.h')
| -rw-r--r-- | lib/xray/xray_fdr_logging_impl.h | 705 |
1 files changed, 0 insertions, 705 deletions
diff --git a/lib/xray/xray_fdr_logging_impl.h b/lib/xray/xray_fdr_logging_impl.h deleted file mode 100644 index 59eab55b2573..000000000000 --- a/lib/xray/xray_fdr_logging_impl.h +++ /dev/null @@ -1,705 +0,0 @@ -//===-- xray_fdr_logging_impl.h ---------------------------------*- 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. -// -// Here we implement the thread local state management and record i/o for Flight -// Data Recorder mode for XRay, where we use compact structures to store records -// in memory as well as when writing out the data to files. -// -//===----------------------------------------------------------------------===// -#ifndef XRAY_XRAY_FDR_LOGGING_IMPL_H -#define XRAY_XRAY_FDR_LOGGING_IMPL_H - -#include <cassert> -#include <cstddef> -#include <cstring> -#include <limits> -#include <pthread.h> -#include <sys/syscall.h> -#include <time.h> -#include <type_traits> -#include <unistd.h> - -#include "sanitizer_common/sanitizer_common.h" -#include "xray/xray_log_interface.h" -#include "xray_buffer_queue.h" -#include "xray_defs.h" -#include "xray_fdr_log_records.h" -#include "xray_flags.h" -#include "xray_tsc.h" - -namespace __xray { - -__sanitizer::atomic_sint32_t LoggingStatus = { - XRayLogInitStatus::XRAY_LOG_UNINITIALIZED}; - -/// We expose some of the state transitions when FDR logging mode is operating -/// such that we can simulate a series of log events that may occur without -/// and test with determinism without worrying about the real CPU time. -/// -/// Because the code uses thread_local allocation extensively as part of its -/// design, callers that wish to test events occuring on different threads -/// will actually have to run them on different threads. -/// -/// This also means that it is possible to break invariants maintained by -/// cooperation with xray_fdr_logging class, so be careful and think twice. -namespace __xray_fdr_internal { - -/// Writes the new buffer record and wallclock time that begin a buffer for the -/// current thread. -static void writeNewBufferPreamble(pid_t Tid, timespec TS); - -/// Writes a Function Record to the buffer associated with the current thread. -static void writeFunctionRecord(int FuncId, uint32_t TSCDelta, - XRayEntryType EntryType); - -/// Sets up a new buffer in thread_local storage and writes a preamble. The -/// wall_clock_reader function is used to populate the WallTimeRecord entry. -static void setupNewBuffer(int (*wall_clock_reader)(clockid_t, - struct timespec *)); - -/// TSC Wrap records are written when a TSC delta encoding scheme overflows. -static void writeTSCWrapMetadata(uint64_t TSC); - -// Group together thread-local-data in a struct, then hide it behind a function -// call so that it can be initialized on first use instead of as a global. We -// force the alignment to 64-bytes for x86 cache line alignment, as this -// structure is used in the hot path of implementation. -struct alignas(64) ThreadLocalData { - BufferQueue::Buffer Buffer; - char *RecordPtr = nullptr; - // The number of FunctionEntry records immediately preceding RecordPtr. - uint8_t NumConsecutiveFnEnters = 0; - - // The number of adjacent, consecutive pairs of FunctionEntry, Tail Exit - // records preceding RecordPtr. - uint8_t NumTailCalls = 0; - - // We use a thread_local variable to keep track of which CPUs we've already - // run, and the TSC times for these CPUs. This allows us to stop repeating the - // CPU field in the function records. - // - // We assume that we'll support only 65536 CPUs for x86_64. - uint16_t CurrentCPU = std::numeric_limits<uint16_t>::max(); - uint64_t LastTSC = 0; - uint64_t LastFunctionEntryTSC = 0; - - // Make sure a thread that's ever called handleArg0 has a thread-local - // live reference to the buffer queue for this particular instance of - // FDRLogging, and that we're going to clean it up when the thread exits. - BufferQueue *BQ = nullptr; -}; - -static_assert(std::is_trivially_destructible<ThreadLocalData>::value, - "ThreadLocalData must be trivially destructible"); - -static constexpr auto MetadataRecSize = sizeof(MetadataRecord); -static constexpr auto FunctionRecSize = sizeof(FunctionRecord); - -// Use a global pthread key to identify thread-local data for logging. -static pthread_key_t Key; - -// This function will initialize the thread-local data structure used by the FDR -// logging implementation and return a reference to it. The implementation -// details require a bit of care to maintain. -// -// First, some requirements on the implementation in general: -// -// - XRay handlers should not call any memory allocation routines that may -// delegate to an instrumented implementation. This means functions like -// malloc() and free() should not be called while instrumenting. -// -// - We would like to use some thread-local data initialized on first-use of -// the XRay instrumentation. These allow us to implement unsynchronized -// routines that access resources associated with the thread. -// -// The implementation here uses a few mechanisms that allow us to provide both -// the requirements listed above. We do this by: -// -// 1. Using a thread-local aligned storage buffer for representing the -// ThreadLocalData struct. This data will be uninitialized memory by -// design. -// -// 2. Not requiring a thread exit handler/implementation, keeping the -// thread-local as purely a collection of references/data that do not -// require cleanup. -// -// We're doing this to avoid using a `thread_local` object that has a -// non-trivial destructor, because the C++ runtime might call std::malloc(...) -// to register calls to destructors. Deadlocks may arise when, for example, an -// externally provided malloc implementation is XRay instrumented, and -// initializing the thread-locals involves calling into malloc. A malloc -// implementation that does global synchronization might be holding a lock for a -// critical section, calling a function that might be XRay instrumented (and -// thus in turn calling into malloc by virtue of registration of the -// thread_local's destructor). -static ThreadLocalData &getThreadLocalData() { - static_assert(alignof(ThreadLocalData) >= 64, - "ThreadLocalData must be cache line aligned."); - thread_local ThreadLocalData TLD; - thread_local bool UNUSED ThreadOnce = [] { - pthread_setspecific(Key, &TLD); - return false; - }(); - return TLD; -} - -//-----------------------------------------------------------------------------| -// The rest of the file is implementation. | -//-----------------------------------------------------------------------------| -// Functions are implemented in the header for inlining since we don't want | -// to grow the stack when we've hijacked the binary for logging. | -//-----------------------------------------------------------------------------| - -namespace { - -class RecursionGuard { - volatile bool &Running; - const bool Valid; - -public: - explicit RecursionGuard(volatile bool &R) : Running(R), Valid(!R) { - if (Valid) - Running = true; - } - - RecursionGuard(const RecursionGuard &) = delete; - RecursionGuard(RecursionGuard &&) = delete; - RecursionGuard &operator=(const RecursionGuard &) = delete; - RecursionGuard &operator=(RecursionGuard &&) = delete; - - explicit operator bool() const { return Valid; } - - ~RecursionGuard() noexcept { - if (Valid) - Running = false; - } -}; - -} // namespace - -static void writeNewBufferPreamble(pid_t Tid, - timespec TS) XRAY_NEVER_INSTRUMENT { - static constexpr int InitRecordsCount = 2; - auto &TLD = getThreadLocalData(); - MetadataRecord Metadata[InitRecordsCount]; - { - // Write out a MetadataRecord to signify that this is the start of a new - // buffer, associated with a particular thread, with a new CPU. For the - // data, we have 15 bytes to squeeze as much information as we can. At this - // point we only write down the following bytes: - // - Thread ID (pid_t, 4 bytes) - auto &NewBuffer = Metadata[0]; - NewBuffer.Type = uint8_t(RecordType::Metadata); - NewBuffer.RecordKind = uint8_t(MetadataRecord::RecordKinds::NewBuffer); - std::memcpy(&NewBuffer.Data, &Tid, sizeof(pid_t)); - } - - // Also write the WalltimeMarker record. - { - static_assert(sizeof(time_t) <= 8, "time_t needs to be at most 8 bytes"); - auto &WalltimeMarker = Metadata[1]; - WalltimeMarker.Type = uint8_t(RecordType::Metadata); - WalltimeMarker.RecordKind = - uint8_t(MetadataRecord::RecordKinds::WalltimeMarker); - - // We only really need microsecond precision here, and enforce across - // platforms that we need 64-bit seconds and 32-bit microseconds encoded in - // the Metadata record. - int32_t Micros = TS.tv_nsec / 1000; - int64_t Seconds = TS.tv_sec; - std::memcpy(WalltimeMarker.Data, &Seconds, sizeof(Seconds)); - std::memcpy(WalltimeMarker.Data + sizeof(Seconds), &Micros, sizeof(Micros)); - } - - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; - if (TLD.BQ == nullptr || TLD.BQ->finalizing()) - return; - std::memcpy(TLD.RecordPtr, Metadata, sizeof(Metadata)); - TLD.RecordPtr += sizeof(Metadata); - // Since we write out the extents as the first metadata record of the - // buffer, we need to write out the extents including the extents record. - __sanitizer::atomic_store(&TLD.Buffer.Extents->Size, sizeof(Metadata), - __sanitizer::memory_order_release); -} - -inline void setupNewBuffer(int (*wall_clock_reader)( - clockid_t, struct timespec *)) XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - auto &B = TLD.Buffer; - TLD.RecordPtr = static_cast<char *>(B.Buffer); - pid_t Tid = syscall(SYS_gettid); - timespec TS{0, 0}; - // This is typically clock_gettime, but callers have injection ability. - wall_clock_reader(CLOCK_MONOTONIC, &TS); - writeNewBufferPreamble(Tid, TS); - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; -} - -static void incrementExtents(size_t Add) { - auto &TLD = getThreadLocalData(); - __sanitizer::atomic_fetch_add(&TLD.Buffer.Extents->Size, Add, - __sanitizer::memory_order_acq_rel); -} - -static void decrementExtents(size_t Subtract) { - auto &TLD = getThreadLocalData(); - __sanitizer::atomic_fetch_sub(&TLD.Buffer.Extents->Size, Subtract, - __sanitizer::memory_order_acq_rel); -} - -inline void writeNewCPUIdMetadata(uint16_t CPU, - uint64_t TSC) XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - MetadataRecord NewCPUId; - NewCPUId.Type = uint8_t(RecordType::Metadata); - NewCPUId.RecordKind = uint8_t(MetadataRecord::RecordKinds::NewCPUId); - - // The data for the New CPU will contain the following bytes: - // - CPU ID (uint16_t, 2 bytes) - // - Full TSC (uint64_t, 8 bytes) - // Total = 10 bytes. - std::memcpy(&NewCPUId.Data, &CPU, sizeof(CPU)); - std::memcpy(&NewCPUId.Data[sizeof(CPU)], &TSC, sizeof(TSC)); - std::memcpy(TLD.RecordPtr, &NewCPUId, sizeof(MetadataRecord)); - TLD.RecordPtr += sizeof(MetadataRecord); - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; - incrementExtents(sizeof(MetadataRecord)); -} - -inline void writeTSCWrapMetadata(uint64_t TSC) XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - MetadataRecord TSCWrap; - TSCWrap.Type = uint8_t(RecordType::Metadata); - TSCWrap.RecordKind = uint8_t(MetadataRecord::RecordKinds::TSCWrap); - - // The data for the TSCWrap record contains the following bytes: - // - Full TSC (uint64_t, 8 bytes) - // Total = 8 bytes. - std::memcpy(&TSCWrap.Data, &TSC, sizeof(TSC)); - std::memcpy(TLD.RecordPtr, &TSCWrap, sizeof(MetadataRecord)); - TLD.RecordPtr += sizeof(MetadataRecord); - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; - incrementExtents(sizeof(MetadataRecord)); -} - -// Call Argument metadata records store the arguments to a function in the -// order of their appearance; holes are not supported by the buffer format. -static inline void writeCallArgumentMetadata(uint64_t A) XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - MetadataRecord CallArg; - CallArg.Type = uint8_t(RecordType::Metadata); - CallArg.RecordKind = uint8_t(MetadataRecord::RecordKinds::CallArgument); - - std::memcpy(CallArg.Data, &A, sizeof(A)); - std::memcpy(TLD.RecordPtr, &CallArg, sizeof(MetadataRecord)); - TLD.RecordPtr += sizeof(MetadataRecord); - incrementExtents(sizeof(MetadataRecord)); -} - -static inline void -writeFunctionRecord(int FuncId, uint32_t TSCDelta, - XRayEntryType EntryType) XRAY_NEVER_INSTRUMENT { - FunctionRecord FuncRecord; - FuncRecord.Type = uint8_t(RecordType::Function); - // Only take 28 bits of the function id. - FuncRecord.FuncId = FuncId & ~(0x0F << 28); - FuncRecord.TSCDelta = TSCDelta; - - auto &TLD = getThreadLocalData(); - switch (EntryType) { - case XRayEntryType::ENTRY: - ++TLD.NumConsecutiveFnEnters; - FuncRecord.RecordKind = uint8_t(FunctionRecord::RecordKinds::FunctionEnter); - break; - case XRayEntryType::LOG_ARGS_ENTRY: - // We should not rewind functions with logged args. - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; - FuncRecord.RecordKind = uint8_t(FunctionRecord::RecordKinds::FunctionEnter); - break; - case XRayEntryType::EXIT: - // If we've decided to log the function exit, we will never erase the log - // before it. - TLD.NumConsecutiveFnEnters = 0; - TLD.NumTailCalls = 0; - FuncRecord.RecordKind = uint8_t(FunctionRecord::RecordKinds::FunctionExit); - break; - case XRayEntryType::TAIL: - // If we just entered the function we're tail exiting from or erased every - // invocation since then, this function entry tail pair is a candidate to - // be erased when the child function exits. - if (TLD.NumConsecutiveFnEnters > 0) { - ++TLD.NumTailCalls; - TLD.NumConsecutiveFnEnters = 0; - } else { - // We will never be able to erase this tail call since we have logged - // something in between the function entry and tail exit. - TLD.NumTailCalls = 0; - TLD.NumConsecutiveFnEnters = 0; - } - FuncRecord.RecordKind = - uint8_t(FunctionRecord::RecordKinds::FunctionTailExit); - break; - case XRayEntryType::CUSTOM_EVENT: { - // This is a bug in patching, so we'll report it once and move on. - static bool Once = [&] { - Report("Internal error: patched an XRay custom event call as a function; " - "func id = %d\n", - FuncId); - return true; - }(); - (void)Once; - return; - } - } - - std::memcpy(TLD.RecordPtr, &FuncRecord, sizeof(FunctionRecord)); - TLD.RecordPtr += sizeof(FunctionRecord); - incrementExtents(sizeof(FunctionRecord)); -} - -static uint64_t thresholdTicks() { - static uint64_t TicksPerSec = probeRequiredCPUFeatures() - ? getTSCFrequency() - : __xray::NanosecondsPerSecond; - static const uint64_t ThresholdTicks = - TicksPerSec * flags()->xray_fdr_log_func_duration_threshold_us / 1000000; - return ThresholdTicks; -} - -// Re-point the thread local pointer into this thread's Buffer before the recent -// "Function Entry" record and any "Tail Call Exit" records after that. -static void rewindRecentCall(uint64_t TSC, uint64_t &LastTSC, - uint64_t &LastFunctionEntryTSC, int32_t FuncId) { - auto &TLD = getThreadLocalData(); - TLD.RecordPtr -= FunctionRecSize; - decrementExtents(FunctionRecSize); - FunctionRecord FuncRecord; - std::memcpy(&FuncRecord, TLD.RecordPtr, FunctionRecSize); - assert(FuncRecord.RecordKind == - uint8_t(FunctionRecord::RecordKinds::FunctionEnter) && - "Expected to find function entry recording when rewinding."); - assert(FuncRecord.FuncId == (FuncId & ~(0x0F << 28)) && - "Expected matching function id when rewinding Exit"); - --TLD.NumConsecutiveFnEnters; - LastTSC -= FuncRecord.TSCDelta; - - // We unwound one call. Update the state and return without writing a log. - if (TLD.NumConsecutiveFnEnters != 0) { - LastFunctionEntryTSC -= FuncRecord.TSCDelta; - return; - } - - // Otherwise we've rewound the stack of all function entries, we might be - // able to rewind further by erasing tail call functions that are being - // exited from via this exit. - LastFunctionEntryTSC = 0; - auto RewindingTSC = LastTSC; - auto RewindingRecordPtr = TLD.RecordPtr - FunctionRecSize; - while (TLD.NumTailCalls > 0) { - // Rewind the TSC back over the TAIL EXIT record. - FunctionRecord ExpectedTailExit; - std::memcpy(&ExpectedTailExit, RewindingRecordPtr, FunctionRecSize); - - assert(ExpectedTailExit.RecordKind == - uint8_t(FunctionRecord::RecordKinds::FunctionTailExit) && - "Expected to find tail exit when rewinding."); - RewindingRecordPtr -= FunctionRecSize; - RewindingTSC -= ExpectedTailExit.TSCDelta; - FunctionRecord ExpectedFunctionEntry; - std::memcpy(&ExpectedFunctionEntry, RewindingRecordPtr, FunctionRecSize); - assert(ExpectedFunctionEntry.RecordKind == - uint8_t(FunctionRecord::RecordKinds::FunctionEnter) && - "Expected to find function entry when rewinding tail call."); - assert(ExpectedFunctionEntry.FuncId == ExpectedTailExit.FuncId && - "Expected funcids to match when rewinding tail call."); - - // This tail call exceeded the threshold duration. It will not be erased. - if ((TSC - RewindingTSC) >= thresholdTicks()) { - TLD.NumTailCalls = 0; - return; - } - - // We can erase a tail exit pair that we're exiting through since - // its duration is under threshold. - --TLD.NumTailCalls; - RewindingRecordPtr -= FunctionRecSize; - RewindingTSC -= ExpectedFunctionEntry.TSCDelta; - TLD.RecordPtr -= 2 * FunctionRecSize; - LastTSC = RewindingTSC; - decrementExtents(2 * FunctionRecSize); - } -} - -inline bool releaseThreadLocalBuffer(BufferQueue &BQArg) { - auto &TLD = getThreadLocalData(); - auto EC = BQArg.releaseBuffer(TLD.Buffer); - if (EC != BufferQueue::ErrorCode::Ok) { - Report("Failed to release buffer at %p; error=%s\n", TLD.Buffer.Buffer, - BufferQueue::getErrorString(EC)); - return false; - } - return true; -} - -inline bool prepareBuffer(uint64_t TSC, unsigned char CPU, - int (*wall_clock_reader)(clockid_t, - struct timespec *), - size_t MaxSize) XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - char *BufferStart = static_cast<char *>(TLD.Buffer.Buffer); - if ((TLD.RecordPtr + MaxSize) > (BufferStart + TLD.Buffer.Size)) { - if (!releaseThreadLocalBuffer(*TLD.BQ)) - return false; - auto EC = TLD.BQ->getBuffer(TLD.Buffer); - if (EC != BufferQueue::ErrorCode::Ok) { - Report("Failed to acquire a buffer; error=%s\n", - BufferQueue::getErrorString(EC)); - return false; - } - setupNewBuffer(wall_clock_reader); - - // Always write the CPU metadata as the first record in the buffer. - writeNewCPUIdMetadata(CPU, TSC); - } - return true; -} - -inline bool -isLogInitializedAndReady(BufferQueue *LBQ, uint64_t TSC, unsigned char CPU, - int (*wall_clock_reader)(clockid_t, struct timespec *)) - XRAY_NEVER_INSTRUMENT { - // Bail out right away if logging is not initialized yet. - // We should take the opportunity to release the buffer though. - auto Status = __sanitizer::atomic_load(&LoggingStatus, - __sanitizer::memory_order_acquire); - auto &TLD = getThreadLocalData(); - if (Status != XRayLogInitStatus::XRAY_LOG_INITIALIZED) { - if (TLD.RecordPtr != nullptr && - (Status == XRayLogInitStatus::XRAY_LOG_FINALIZING || - Status == XRayLogInitStatus::XRAY_LOG_FINALIZED)) { - if (!releaseThreadLocalBuffer(*LBQ)) - return false; - TLD.RecordPtr = nullptr; - return false; - } - return false; - } - - if (__sanitizer::atomic_load(&LoggingStatus, - __sanitizer::memory_order_acquire) != - XRayLogInitStatus::XRAY_LOG_INITIALIZED || - LBQ->finalizing()) { - if (!releaseThreadLocalBuffer(*LBQ)) - return false; - TLD.RecordPtr = nullptr; - } - - if (TLD.Buffer.Buffer == nullptr) { - auto EC = LBQ->getBuffer(TLD.Buffer); - if (EC != BufferQueue::ErrorCode::Ok) { - auto LS = __sanitizer::atomic_load(&LoggingStatus, - __sanitizer::memory_order_acquire); - if (LS != XRayLogInitStatus::XRAY_LOG_FINALIZING && - LS != XRayLogInitStatus::XRAY_LOG_FINALIZED) - Report("Failed to acquire a buffer; error=%s\n", - BufferQueue::getErrorString(EC)); - return false; - } - - setupNewBuffer(wall_clock_reader); - - // Always write the CPU metadata as the first record in the buffer. - writeNewCPUIdMetadata(CPU, TSC); - } - - if (TLD.CurrentCPU == std::numeric_limits<uint16_t>::max()) { - // This means this is the first CPU this thread has ever run on. We set - // the current CPU and record this as the first TSC we've seen. - TLD.CurrentCPU = CPU; - writeNewCPUIdMetadata(CPU, TSC); - } - - return true; -} // namespace __xray_fdr_internal - -// Compute the TSC difference between the time of measurement and the previous -// event. There are a few interesting situations we need to account for: -// -// - The thread has migrated to a different CPU. If this is the case, then -// we write down the following records: -// -// 1. A 'NewCPUId' Metadata record. -// 2. A FunctionRecord with a 0 for the TSCDelta field. -// -// - The TSC delta is greater than the 32 bits we can store in a -// FunctionRecord. In this case we write down the following records: -// -// 1. A 'TSCWrap' Metadata record. -// 2. A FunctionRecord with a 0 for the TSCDelta field. -// -// - The TSC delta is representable within the 32 bits we can store in a -// FunctionRecord. In this case we write down just a FunctionRecord with -// the correct TSC delta. -inline uint32_t writeCurrentCPUTSC(ThreadLocalData &TLD, uint64_t TSC, - uint8_t CPU) { - if (CPU != TLD.CurrentCPU) { - // We've moved to a new CPU. - writeNewCPUIdMetadata(CPU, TSC); - return 0; - } - // If the delta is greater than the range for a uint32_t, then we write out - // the TSC wrap metadata entry with the full TSC, and the TSC for the - // function record be 0. - uint64_t Delta = TSC - TLD.LastTSC; - if (Delta <= std::numeric_limits<uint32_t>::max()) - return Delta; - - writeTSCWrapMetadata(TSC); - return 0; -} - -inline void endBufferIfFull() XRAY_NEVER_INSTRUMENT { - auto &TLD = getThreadLocalData(); - auto BufferStart = static_cast<char *>(TLD.Buffer.Buffer); - if ((TLD.RecordPtr + MetadataRecSize) - BufferStart <= - ptrdiff_t{MetadataRecSize}) { - if (!releaseThreadLocalBuffer(*TLD.BQ)) - return; - TLD.RecordPtr = nullptr; - } -} - -thread_local volatile bool Running = false; - -/// Here's where the meat of the processing happens. The writer captures -/// function entry, exit and tail exit points with a time and will create -/// TSCWrap, NewCPUId and Function records as necessary. The writer might -/// walk backward through its buffer and erase trivial functions to avoid -/// polluting the log and may use the buffer queue to obtain or release a -/// buffer. -inline void processFunctionHook(int32_t FuncId, XRayEntryType Entry, - uint64_t TSC, unsigned char CPU, uint64_t Arg1, - int (*wall_clock_reader)(clockid_t, - struct timespec *), - BufferQueue *BQ) XRAY_NEVER_INSTRUMENT { - // Prevent signal handler recursion, so in case we're already in a log writing - // mode and the signal handler comes in (and is also instrumented) then we - // don't want to be clobbering potentially partial writes already happening in - // the thread. We use a simple thread_local latch to only allow one on-going - // handleArg0 to happen at any given time. - RecursionGuard Guard{Running}; - if (!Guard) { - assert(Running == true && "RecursionGuard is buggy!"); - return; - } - - auto &TLD = getThreadLocalData(); - - // In case the reference has been cleaned up before, we make sure we - // initialize it to the provided BufferQueue. - if (TLD.BQ == nullptr) - TLD.BQ = BQ; - - if (!isLogInitializedAndReady(TLD.BQ, TSC, CPU, wall_clock_reader)) - return; - - // Before we go setting up writing new function entries, we need to be really - // careful about the pointer math we're doing. This means we need to ensure - // that the record we are about to write is going to fit into the buffer, - // without overflowing the buffer. - // - // To do this properly, we use the following assumptions: - // - // - The least number of bytes we will ever write is 8 - // (sizeof(FunctionRecord)) only if the delta between the previous entry - // and this entry is within 32 bits. - // - The most number of bytes we will ever write is 8 + 16 + 16 = 40. - // This is computed by: - // - // MaxSize = sizeof(FunctionRecord) + 2 * sizeof(MetadataRecord) - // - // These arise in the following cases: - // - // 1. When the delta between the TSC we get and the previous TSC for the - // same CPU is outside of the uint32_t range, we end up having to - // write a MetadataRecord to indicate a "tsc wrap" before the actual - // FunctionRecord. - // 2. When we learn that we've moved CPUs, we need to write a - // MetadataRecord to indicate a "cpu change", and thus write out the - // current TSC for that CPU before writing out the actual - // FunctionRecord. - // 3. When we learn about a new CPU ID, we need to write down a "new cpu - // id" MetadataRecord before writing out the actual FunctionRecord. - // 4. The second MetadataRecord is the optional function call argument. - // - // So the math we need to do is to determine whether writing 40 bytes past the - // current pointer exceeds the buffer's maximum size. If we don't have enough - // space to write 40 bytes in the buffer, we need get a new Buffer, set it up - // properly before doing any further writing. - size_t MaxSize = FunctionRecSize + 2 * MetadataRecSize; - if (!prepareBuffer(TSC, CPU, wall_clock_reader, MaxSize)) { - TLD.BQ = nullptr; - return; - } - - // By this point, we are now ready to write up to 40 bytes (explained above). - assert((TLD.RecordPtr + MaxSize) - static_cast<char *>(TLD.Buffer.Buffer) >= - static_cast<ptrdiff_t>(MetadataRecSize) && - "Misconfigured BufferQueue provided; Buffer size not large enough."); - - auto RecordTSCDelta = writeCurrentCPUTSC(TLD, TSC, CPU); - TLD.LastTSC = TSC; - TLD.CurrentCPU = CPU; - switch (Entry) { - case XRayEntryType::ENTRY: - case XRayEntryType::LOG_ARGS_ENTRY: - // Update the thread local state for the next invocation. - TLD.LastFunctionEntryTSC = TSC; - break; - case XRayEntryType::TAIL: - case XRayEntryType::EXIT: - // Break out and write the exit record if we can't erase any functions. - if (TLD.NumConsecutiveFnEnters == 0 || - (TSC - TLD.LastFunctionEntryTSC) >= thresholdTicks()) - break; - rewindRecentCall(TSC, TLD.LastTSC, TLD.LastFunctionEntryTSC, FuncId); - return; // without writing log. - case XRayEntryType::CUSTOM_EVENT: { - // This is a bug in patching, so we'll report it once and move on. - static bool Once = [&] { - Report("Internal error: patched an XRay custom event call as a function; " - "func id = %d", - FuncId); - return true; - }(); - (void)Once; - return; - } - } - - writeFunctionRecord(FuncId, RecordTSCDelta, Entry); - if (Entry == XRayEntryType::LOG_ARGS_ENTRY) - writeCallArgumentMetadata(Arg1); - - // If we've exhausted the buffer by this time, we then release the buffer to - // make sure that other threads may start using this buffer. - endBufferIfFull(); -} - -} // namespace __xray_fdr_internal -} // namespace __xray - -#endif // XRAY_XRAY_FDR_LOGGING_IMPL_H |