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Diffstat (limited to 'compiler-rt/lib/xray/xray_fdr_logging_impl.h')
| -rw-r--r-- | compiler-rt/lib/xray/xray_fdr_logging_impl.h | 486 |
1 files changed, 486 insertions, 0 deletions
diff --git a/compiler-rt/lib/xray/xray_fdr_logging_impl.h b/compiler-rt/lib/xray/xray_fdr_logging_impl.h new file mode 100644 index 00000000000..a06b22df920 --- /dev/null +++ b/compiler-rt/lib/xray/xray_fdr_logging_impl.h @@ -0,0 +1,486 @@ +//===-- 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 <cstdint> +#include <cstring> +#include <memory> +#include <sys/syscall.h> +#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" + +namespace __xray { + +/// 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 a +/// thread to MemPtr and increments MemPtr. Bypasses the thread local state +// machine and writes directly to memory without checks. +static void writeNewBufferPreamble(pid_t Tid, timespec TS, char *&MemPtr); + +/// Write a metadata record to switch to a new CPU to MemPtr and increments +/// MemPtr. Bypasses the thread local state machine and writes directly to +/// memory without checks. +static void writeNewCPUIdMetadata(uint16_t CPU, uint64_t TSC, char *&MemPtr); + +/// Writes an EOB metadata record to MemPtr and increments MemPtr. Bypasses the +/// thread local state machine and writes directly to memory without checks. +static void writeEOBMetadata(char *&MemPtr); + +/// Writes a TSC Wrap metadata record to MemPtr and increments MemPtr. Bypasses +/// the thread local state machine and directly writes to memory without checks. +static void writeTSCWrapMetadata(uint64_t TSC, char *&MemPtr); + +/// Writes a Function Record to MemPtr and increments MemPtr. Bypasses the +/// thread local state machine and writes the function record directly to +/// memory. +static void writeFunctionRecord(int FuncId, uint32_t TSCDelta, + XRayEntryType EntryType, char *&MemPtr); + +/// 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(const BufferQueue::Buffer &Buffer, + int (*wall_clock_reader)(clockid_t, + struct timespec *)); + +/// Called to record CPU time for a new CPU within the current thread. +static void writeNewCPUIdMetadata(uint16_t CPU, uint64_t TSC); + +/// Called to close the buffer when the thread exhausts the buffer or when the +/// thread exits (via a thread local variable destructor). +static void writeEOBMetadata(); + +/// TSC Wrap records are written when a TSC delta encoding scheme overflows. +static void writeTSCWrapMetadata(uint64_t TSC); + +/// 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. +static void +processFunctionHook(int32_t FuncId, XRayEntryType Entry, uint64_t TSC, + unsigned char CPU, + int (*wall_clock_reader)(clockid_t, struct timespec *), + const std::atomic<XRayLogInitStatus> &LoggingStatus, + const std::shared_ptr<BufferQueue> &BQ); + +//-----------------------------------------------------------------------------| +// 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 { +thread_local BufferQueue::Buffer Buffer; +thread_local char *RecordPtr = nullptr; + +constexpr auto MetadataRecSize = sizeof(MetadataRecord); +constexpr auto FunctionRecSize = sizeof(FunctionRecord); + +class ThreadExitBufferCleanup { + std::weak_ptr<BufferQueue> Buffers; + BufferQueue::Buffer &Buffer; + +public: + explicit ThreadExitBufferCleanup(std::weak_ptr<BufferQueue> BQ, + BufferQueue::Buffer &Buffer) + XRAY_NEVER_INSTRUMENT : Buffers(BQ), + Buffer(Buffer) {} + + ~ThreadExitBufferCleanup() noexcept XRAY_NEVER_INSTRUMENT { + if (RecordPtr == nullptr) + return; + + // We make sure that upon exit, a thread will write out the EOB + // MetadataRecord in the thread-local log, and also release the buffer to + // the queue. + assert((RecordPtr + MetadataRecSize) - static_cast<char *>(Buffer.Buffer) >= + static_cast<ptrdiff_t>(MetadataRecSize)); + if (auto BQ = Buffers.lock()) { + writeEOBMetadata(); + if (auto EC = BQ->releaseBuffer(Buffer)) + Report("Failed to release buffer at %p; error=%s\n", Buffer.Buffer, + EC.message().c_str()); + return; + } + } +}; + +class RecursionGuard { + bool &Running; + const bool Valid; + +public: + explicit RecursionGuard(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; + } +}; + +static inline bool loggingInitialized( + const std::atomic<XRayLogInitStatus> &LoggingStatus) XRAY_NEVER_INSTRUMENT { + return LoggingStatus.load(std::memory_order_acquire) == + XRayLogInitStatus::XRAY_LOG_INITIALIZED; +} + +} // namespace anonymous + +static inline void writeNewBufferPreamble(pid_t Tid, timespec TS, + char *&MemPtr) XRAY_NEVER_INSTRUMENT { + static constexpr int InitRecordsCount = 2; + std::aligned_storage<sizeof(MetadataRecord)>::type Records[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 = *reinterpret_cast<MetadataRecord *>(&Records[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 = *reinterpret_cast<MetadataRecord *>(&Records[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)); + } + std::memcpy(MemPtr, Records, sizeof(MetadataRecord) * InitRecordsCount); + MemPtr += sizeof(MetadataRecord) * InitRecordsCount; +} + +static inline void setupNewBuffer(const BufferQueue::Buffer &Buffer, + int (*wall_clock_reader)(clockid_t, + struct timespec *)) + XRAY_NEVER_INSTRUMENT { + RecordPtr = static_cast<char *>(Buffer.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, RecordPtr); +} + +static inline void writeNewCPUIdMetadata(uint16_t CPU, uint64_t TSC, + char *&MemPtr) XRAY_NEVER_INSTRUMENT { + 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 = 12 bytes. + std::memcpy(&NewCPUId.Data, &CPU, sizeof(CPU)); + std::memcpy(&NewCPUId.Data[sizeof(CPU)], &TSC, sizeof(TSC)); + std::memcpy(MemPtr, &NewCPUId, sizeof(MetadataRecord)); + MemPtr += sizeof(MetadataRecord); +} + +static inline void writeNewCPUIdMetadata(uint16_t CPU, + uint64_t TSC) XRAY_NEVER_INSTRUMENT { + writeNewCPUIdMetadata(CPU, TSC, RecordPtr); +} + +static inline void writeEOBMetadata(char *&MemPtr) XRAY_NEVER_INSTRUMENT { + MetadataRecord EOBMeta; + EOBMeta.Type = uint8_t(RecordType::Metadata); + EOBMeta.RecordKind = uint8_t(MetadataRecord::RecordKinds::EndOfBuffer); + // For now we don't write any bytes into the Data field. + std::memcpy(MemPtr, &EOBMeta, sizeof(MetadataRecord)); + MemPtr += sizeof(MetadataRecord); +} + +static inline void writeEOBMetadata() XRAY_NEVER_INSTRUMENT { + writeEOBMetadata(RecordPtr); +} + +static inline void writeTSCWrapMetadata(uint64_t TSC, + char *&MemPtr) XRAY_NEVER_INSTRUMENT { + 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(MemPtr, &TSCWrap, sizeof(MetadataRecord)); + MemPtr += sizeof(MetadataRecord); +} + +static inline void writeTSCWrapMetadata(uint64_t TSC) XRAY_NEVER_INSTRUMENT { + writeTSCWrapMetadata(TSC, RecordPtr); +} + +static inline void writeFunctionRecord(int FuncId, uint32_t TSCDelta, + XRayEntryType EntryType, + char *&MemPtr) XRAY_NEVER_INSTRUMENT { + std::aligned_storage<sizeof(FunctionRecord), alignof(FunctionRecord)>::type + AlignedFuncRecordBuffer; + auto &FuncRecord = + *reinterpret_cast<FunctionRecord *>(&AlignedFuncRecordBuffer); + FuncRecord.Type = uint8_t(RecordType::Function); + // Only take 28 bits of the function id. + FuncRecord.FuncId = FuncId & ~(0x0F << 28); + FuncRecord.TSCDelta = TSCDelta; + + switch (EntryType) { + case XRayEntryType::ENTRY: + case XRayEntryType::LOG_ARGS_ENTRY: + FuncRecord.RecordKind = uint8_t(FunctionRecord::RecordKinds::FunctionEnter); + break; + case XRayEntryType::EXIT: + FuncRecord.RecordKind = uint8_t(FunctionRecord::RecordKinds::FunctionExit); + break; + case XRayEntryType::TAIL: + FuncRecord.RecordKind = + uint8_t(FunctionRecord::RecordKinds::FunctionTailExit); + break; + } + + std::memcpy(MemPtr, &AlignedFuncRecordBuffer, sizeof(FunctionRecord)); + MemPtr += sizeof(FunctionRecord); +} + +static inline void processFunctionHook( + int32_t FuncId, XRayEntryType Entry, uint64_t TSC, unsigned char CPU, + int (*wall_clock_reader)(clockid_t, struct timespec *), + const std::atomic<XRayLogInitStatus> &LoggingStatus, + const std::shared_ptr<BufferQueue> &BQ) XRAY_NEVER_INSTRUMENT { + // Bail out right away if logging is not initialized yet. + if (LoggingStatus.load(std::memory_order_acquire) != + XRayLogInitStatus::XRAY_LOG_INITIALIZED) + return; + + // 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. + thread_local uint16_t CurrentCPU = std::numeric_limits<uint16_t>::max(); + thread_local uint64_t LastTSC = 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. + thread_local auto LocalBQ = BQ; + thread_local ThreadExitBufferCleanup Cleanup(LocalBQ, Buffer); + + // 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. + thread_local bool Running = false; + RecursionGuard Guard{Running}; + if (!Guard) { + assert(Running == true && "RecursionGuard is buggy!"); + return; + } + + if (!loggingInitialized(LoggingStatus) || LocalBQ->finalizing()) { + writeEOBMetadata(); + if (auto EC = BQ->releaseBuffer(Buffer)) { + Report("Failed to release buffer at %p; error=%s\n", Buffer.Buffer, + EC.message().c_str()); + return; + } + RecordPtr = nullptr; + } + + if (Buffer.Buffer == nullptr) { + if (auto EC = LocalBQ->getBuffer(Buffer)) { + auto LS = LoggingStatus.load(std::memory_order_acquire); + if (LS != XRayLogInitStatus::XRAY_LOG_FINALIZING && + LS != XRayLogInitStatus::XRAY_LOG_FINALIZED) + Report("Failed to acquire a buffer; error=%s\n", EC.message().c_str()); + return; + } + + setupNewBuffer(Buffer, wall_clock_reader); + } + + if (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. + CurrentCPU = CPU; + writeNewCPUIdMetadata(CPU, TSC); + } + + // 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 = 24. This is + // computed by: + // + // sizeof(FunctionRecord) + 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. + // + // - An End-of-Buffer (EOB) MetadataRecord is 16 bytes. + // + // So the math we need to do is to determine whether writing 24 bytes past the + // current pointer leaves us with enough bytes to write the EOB + // MetadataRecord. If we don't have enough space after writing as much as 24 + // bytes in the end of the buffer, we need to write out the EOB, get a new + // Buffer, set it up properly before doing any further writing. + // + char *BufferStart = static_cast<char *>(Buffer.Buffer); + if ((RecordPtr + (MetadataRecSize + FunctionRecSize)) - BufferStart < + static_cast<ptrdiff_t>(MetadataRecSize)) { + writeEOBMetadata(); + if (auto EC = LocalBQ->releaseBuffer(Buffer)) { + Report("Failed to release buffer at %p; error=%s\n", Buffer.Buffer, + EC.message().c_str()); + return; + } + if (auto EC = LocalBQ->getBuffer(Buffer)) { + Report("Failed to acquire a buffer; error=%s\n", EC.message().c_str()); + return; + } + setupNewBuffer(Buffer, wall_clock_reader); + } + + // By this point, we are now ready to write at most 24 bytes (one metadata + // record and one function record). + BufferStart = static_cast<char *>(Buffer.Buffer); + assert((RecordPtr + (MetadataRecSize + FunctionRecSize)) - BufferStart >= + static_cast<ptrdiff_t>(MetadataRecSize) && + "Misconfigured BufferQueue provided; Buffer size not large enough."); + + // Here we compute the TSC Delta. 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. + // + + uint32_t RecordTSCDelta = 0; + if (CPU != CurrentCPU) { + // We've moved to a new CPU. + writeNewCPUIdMetadata(CPU, TSC); + } else { + // 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. + auto Delta = TSC - LastTSC; + if (Delta > (1ULL << 32) - 1) + writeTSCWrapMetadata(TSC); + else + RecordTSCDelta = Delta; + } + + // We then update our "LastTSC" and "CurrentCPU" thread-local variables to aid + // us in future computations of this TSC delta value. + LastTSC = TSC; + CurrentCPU = CPU; + + writeFunctionRecord(FuncId, RecordTSCDelta, Entry, RecordPtr); + + // 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. + if ((RecordPtr + MetadataRecSize) - BufferStart == MetadataRecSize) { + writeEOBMetadata(); + if (auto EC = LocalBQ->releaseBuffer(Buffer)) { + Report("Failed releasing buffer at %p; error=%s\n", Buffer.Buffer, + EC.message().c_str()); + return; + } + RecordPtr = nullptr; + } +} + +} // namespace __xray_fdr_internal + +} // namespace __xray + +#endif // XRAY_XRAY_FDR_LOGGING_IMPL_H |
