1//===-- xray_fdr_log_records.h  -------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file is a part of XRay, a function call tracing system.
10//
11//===----------------------------------------------------------------------===//
12#ifndef XRAY_XRAY_FDR_LOG_RECORDS_H
13#define XRAY_XRAY_FDR_LOG_RECORDS_H
14#include <cstdint>
15
16namespace __xray {
17
18enum class RecordType : uint8_t { Function, Metadata };
19
20// A MetadataRecord encodes the kind of record in its first byte, and have 15
21// additional bytes in the end to hold free-form data.
22struct alignas(16) MetadataRecord {
23  // A MetadataRecord must always have a type of 1.
24  /* RecordType */ uint8_t Type : 1;
25
26  // Each kind of record is represented as a 7-bit value (even though we use an
27  // unsigned 8-bit enum class to do so).
28  enum class RecordKinds : uint8_t {
29    NewBuffer,
30    EndOfBuffer,
31    NewCPUId,
32    TSCWrap,
33    WalltimeMarker,
34    CustomEventMarker,
35    CallArgument,
36    BufferExtents,
37    TypedEventMarker,
38    Pid,
39  };
40
41  // Use 7 bits to identify this record type.
42  /* RecordKinds */ uint8_t RecordKind : 7;
43  char Data[15];
44} __attribute__((packed));
45
46static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
47
48struct alignas(8) FunctionRecord {
49  // A FunctionRecord must always have a type of 0.
50  /* RecordType */ uint8_t Type : 1;
51  enum class RecordKinds {
52    FunctionEnter = 0x00,
53    FunctionExit = 0x01,
54    FunctionTailExit = 0x02,
55  };
56  /* RecordKinds */ uint8_t RecordKind : 3;
57
58  // We only use 28 bits of the function ID, so that we can use as few bytes as
59  // possible. This means we only support 2^28 (268,435,456) unique function ids
60  // in a single binary.
61  int FuncId : 28;
62
63  // We use another 4 bytes to hold the delta between the previous entry's TSC.
64  // In case we've found that the distance is greater than the allowable 32 bits
65  // (either because we are running in a different CPU and the TSC might be
66  // different then), we should use a MetadataRecord before this FunctionRecord
67  // that will contain the full TSC for that CPU, and keep this to 0.
68  uint32_t TSCDelta;
69} __attribute__((packed));
70
71static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
72
73} // namespace __xray
74
75#endif // XRAY_XRAY_FDR_LOG_RECORDS_H
76