compiler-rt/lib/xray/xray_fdr_log_records.h

   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
  16 namespace __xray {
  17
  18 enum 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.
  22 struct 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
  46 static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
  47
  48 struct 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
  71 static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
  72
  73 } // namespace __xray
  74
  75 #endif // XRAY_XRAY_FDR_LOG_RECORDS_H