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| //===-- xray_fdr_log_records.h -------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of XRay, a function call tracing system.
//
//===----------------------------------------------------------------------===//
#ifndef XRAY_XRAY_FDR_LOG_RECORDS_H
#define XRAY_XRAY_FDR_LOG_RECORDS_H
#include <cstdint>
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 */ uint8_t 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,
CustomEventMarker,
CallArgument,
BufferExtents,
TypedEventMarker,
Pid,
};
// Use 7 bits to identify this record type.
/* RecordKinds */ uint8_t RecordKind : 7;
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 */ uint8_t Type : 1;
enum class RecordKinds {
FunctionEnter = 0x00,
FunctionExit = 0x01,
FunctionTailExit = 0x02,
};
/* RecordKinds */ uint8_t 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.");
} // namespace __xray
#endif // XRAY_XRAY_FDR_LOG_RECORDS_H
|