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 76