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//===-- xray_fdr_logging.h ------------------------------------------------===//
//
// 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 function call tracing system.
//
//===----------------------------------------------------------------------===//
#ifndef XRAY_XRAY_FDR_LOGGING_H
#define XRAY_XRAY_FDR_LOGGING_H
#include "xray/xray_log_interface.h"
// FDR (Flight Data Recorder) Mode
// ===============================
//
// The XRay whitepaper describes a mode of operation for function call trace
// logging that involves writing small records into an in-memory circular
// buffer, that then gets logged to disk on demand. To do this efficiently and
// capture as much data as we can, we use smaller records compared to the
// default mode of always writing fixed-size records.
namespace __xray {
enum class RecordType : uint8_t {
Function, Metadata
};
// A MetadataRecord encodes the kind of record in its first byte, and have 15
// additional bytes in the end to hold free-form data.
struct alignas(16) MetadataRecord {
// A MetadataRecord must always have a type of 1.
RecordType Type : 1;
// Each kind of record is represented as a 7-bit value (even though we use an
// unsigned 8-bit enum class to do so).
enum class RecordKinds : uint8_t {
NewBuffer,
EndOfBuffer,
NewCPUId,
TSCWrap,
WalltimeMarker,
};
RecordKinds RecordKind : 7; // Use 7 bits to identify this record type.
char Data[15];
} __attribute__((packed));
static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
struct alignas(8) FunctionRecord {
// A FunctionRecord must always have a type of 0.
RecordType Type : 1;
enum class RecordKinds {
FunctionEnter = 0x00,
FunctionExit = 0x01,
FunctionTailExit = 0x02,
};
RecordKinds RecordKind : 3;
// We only use 28 bits of the function ID, so that we can use as few bytes as
// possible. This means we only support 2^28 (268,435,456) unique function ids
// in a single binary.
int FuncId : 28;
// We use another 4 bytes to hold the delta between the previous entry's TSC.
// In case we've found that the distance is greater than the allowable 32 bits
// (either because we are running in a different CPU and the TSC might be
// different then), we should use a MetadataRecord before this FunctionRecord
// that will contain the full TSC for that CPU, and keep this to 0.
uint32_t TSCDelta;
} __attribute__((packed));
static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
// Options used by the FDR implementation.
struct FDRLoggingOptions {
bool ReportErrors = false;
int Fd = -1;
};
// Flight Data Recorder mode implementation interfaces.
XRayLogInitStatus FDRLogging_init(std::size_t BufferSize, std::size_t BufferMax,
void *Options, size_t OptionsSize);
XRayLogInitStatus FDRLogging_finalize();
void FDRLogging_handleArg0(int32_t FuncId, XRayEntryType Entry);
XRayLogFlushStatus FDRLogging_flush();
XRayLogInitStatus FDRLogging_reset();
} // namespace __xray
#endif // XRAY_XRAY_FDR_LOGGING_H
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