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      1 //===-- xray_fdr_log_records.h  -------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file is a part of XRay, a function call tracing system.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 #ifndef XRAY_XRAY_FDR_LOG_RECORDS_H
     14 #define XRAY_XRAY_FDR_LOG_RECORDS_H
     15 #include <cstdint>
     16 
     17 namespace __xray {
     18 
     19 enum class RecordType : uint8_t { Function, Metadata };
     20 
     21 // A MetadataRecord encodes the kind of record in its first byte, and have 15
     22 // additional bytes in the end to hold free-form data.
     23 struct alignas(16) MetadataRecord {
     24   // A MetadataRecord must always have a type of 1.
     25   /* RecordType */ uint8_t Type : 1;
     26 
     27   // Each kind of record is represented as a 7-bit value (even though we use an
     28   // unsigned 8-bit enum class to do so).
     29   enum class RecordKinds : uint8_t {
     30     NewBuffer,
     31     EndOfBuffer,
     32     NewCPUId,
     33     TSCWrap,
     34     WalltimeMarker,
     35     CustomEventMarker,
     36     CallArgument,
     37     BufferExtents,
     38     TypedEventMarker,
     39     Pid,
     40   };
     41 
     42   // Use 7 bits to identify this record type.
     43   /* RecordKinds */ uint8_t RecordKind : 7;
     44   char Data[15];
     45 } __attribute__((packed));
     46 
     47 static_assert(sizeof(MetadataRecord) == 16, "Wrong size for MetadataRecord.");
     48 
     49 struct alignas(8) FunctionRecord {
     50   // A FunctionRecord must always have a type of 0.
     51   /* RecordType */ uint8_t Type : 1;
     52   enum class RecordKinds {
     53     FunctionEnter = 0x00,
     54     FunctionExit = 0x01,
     55     FunctionTailExit = 0x02,
     56   };
     57   /* RecordKinds */ uint8_t RecordKind : 3;
     58 
     59   // We only use 28 bits of the function ID, so that we can use as few bytes as
     60   // possible. This means we only support 2^28 (268,435,456) unique function ids
     61   // in a single binary.
     62   int FuncId : 28;
     63 
     64   // We use another 4 bytes to hold the delta between the previous entry's TSC.
     65   // In case we've found that the distance is greater than the allowable 32 bits
     66   // (either because we are running in a different CPU and the TSC might be
     67   // different then), we should use a MetadataRecord before this FunctionRecord
     68   // that will contain the full TSC for that CPU, and keep this to 0.
     69   uint32_t TSCDelta;
     70 } __attribute__((packed));
     71 
     72 static_assert(sizeof(FunctionRecord) == 8, "Wrong size for FunctionRecord.");
     73 
     74 } // namespace __xray
     75 
     76 #endif // XRAY_XRAY_FDR_LOG_RECORDS_H
     77