1 //===-- tsan_trace.h --------------------------------------------*- C++ -*-===// 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 ThreadSanitizer (TSan), a race detector. 10 // 11 //===----------------------------------------------------------------------===// 12 #ifndef TSAN_TRACE_H 13 #define TSAN_TRACE_H 14 15 #include "tsan_defs.h" 16 #include "tsan_ilist.h" 17 #include "tsan_mutexset.h" 18 #include "tsan_stack_trace.h" 19 20 namespace __tsan { 21 22 enum class EventType : u64 { 23 kAccessExt, 24 kAccessRange, 25 kLock, 26 kRLock, 27 kUnlock, 28 kTime, 29 }; 30 31 // "Base" type for all events for type dispatch. 32 struct Event { 33 // We use variable-length type encoding to give more bits to some event 34 // types that need them. If is_access is set, this is EventAccess. 35 // Otherwise, if is_func is set, this is EventFunc. 36 // Otherwise type denotes the type. 37 u64 is_access : 1; 38 u64 is_func : 1; 39 EventType type : 3; 40 u64 _ : 59; 41 }; 42 static_assert(sizeof(Event) == 8, "bad Event size"); 43 44 // Nop event used as padding and does not affect state during replay. 45 static constexpr Event NopEvent = {1, 0, EventType::kAccessExt, 0}; 46 47 // Compressed memory access can represent only some events with PCs 48 // close enough to each other. Otherwise we fall back to EventAccessExt. 49 struct EventAccess { 50 static constexpr uptr kPCBits = 15; 51 static_assert(kPCBits + kCompressedAddrBits + 5 == 64, 52 "unused bits in EventAccess"); 53 54 u64 is_access : 1; // = 1 55 u64 is_read : 1; 56 u64 is_atomic : 1; 57 u64 size_log : 2; 58 u64 pc_delta : kPCBits; // signed delta from the previous memory access PC 59 u64 addr : kCompressedAddrBits; 60 }; 61 static_assert(sizeof(EventAccess) == 8, "bad EventAccess size"); 62 63 // Function entry (pc != 0) or exit (pc == 0). 64 struct EventFunc { 65 u64 is_access : 1; // = 0 66 u64 is_func : 1; // = 1 67 u64 pc : 62; 68 }; 69 static_assert(sizeof(EventFunc) == 8, "bad EventFunc size"); 70 71 // Extended memory access with full PC. 72 struct EventAccessExt { 73 // Note: precisely specifying the unused parts of the bitfield is critical for 74 // performance. If we don't specify them, compiler will generate code to load 75 // the old value and shuffle it to extract the unused bits to apply to the new 76 // value. If we specify the unused part and store 0 in there, all that 77 // unnecessary code goes away (store of the 0 const is combined with other 78 // constant parts). 79 static constexpr uptr kUnusedBits = 11; 80 static_assert(kCompressedAddrBits + kUnusedBits + 9 == 64, 81 "unused bits in EventAccessExt"); 82 83 u64 is_access : 1; // = 0 84 u64 is_func : 1; // = 0 85 EventType type : 3; // = EventType::kAccessExt 86 u64 is_read : 1; 87 u64 is_atomic : 1; 88 u64 size_log : 2; 89 u64 _ : kUnusedBits; 90 u64 addr : kCompressedAddrBits; 91 u64 pc; 92 }; 93 static_assert(sizeof(EventAccessExt) == 16, "bad EventAccessExt size"); 94 95 // Access to a memory range. 96 struct EventAccessRange { 97 static constexpr uptr kSizeLoBits = 13; 98 static_assert(kCompressedAddrBits + kSizeLoBits + 7 == 64, 99 "unused bits in EventAccessRange"); 100 101 u64 is_access : 1; // = 0 102 u64 is_func : 1; // = 0 103 EventType type : 3; // = EventType::kAccessRange 104 u64 is_read : 1; 105 u64 is_free : 1; 106 u64 size_lo : kSizeLoBits; 107 u64 pc : kCompressedAddrBits; 108 u64 addr : kCompressedAddrBits; 109 u64 size_hi : 64 - kCompressedAddrBits; 110 }; 111 static_assert(sizeof(EventAccessRange) == 16, "bad EventAccessRange size"); 112 113 // Mutex lock. 114 struct EventLock { 115 static constexpr uptr kStackIDLoBits = 15; 116 static constexpr uptr kStackIDHiBits = 117 sizeof(StackID) * kByteBits - kStackIDLoBits; 118 static constexpr uptr kUnusedBits = 3; 119 static_assert(kCompressedAddrBits + kStackIDLoBits + 5 == 64, 120 "unused bits in EventLock"); 121 static_assert(kCompressedAddrBits + kStackIDHiBits + kUnusedBits == 64, 122 "unused bits in EventLock"); 123 124 u64 is_access : 1; // = 0 125 u64 is_func : 1; // = 0 126 EventType type : 3; // = EventType::kLock or EventType::kRLock 127 u64 pc : kCompressedAddrBits; 128 u64 stack_lo : kStackIDLoBits; 129 u64 stack_hi : sizeof(StackID) * kByteBits - kStackIDLoBits; 130 u64 _ : kUnusedBits; 131 u64 addr : kCompressedAddrBits; 132 }; 133 static_assert(sizeof(EventLock) == 16, "bad EventLock size"); 134 135 // Mutex unlock. 136 struct EventUnlock { 137 static constexpr uptr kUnusedBits = 15; 138 static_assert(kCompressedAddrBits + kUnusedBits + 5 == 64, 139 "unused bits in EventUnlock"); 140 141 u64 is_access : 1; // = 0 142 u64 is_func : 1; // = 0 143 EventType type : 3; // = EventType::kUnlock 144 u64 _ : kUnusedBits; 145 u64 addr : kCompressedAddrBits; 146 }; 147 static_assert(sizeof(EventUnlock) == 8, "bad EventUnlock size"); 148 149 // Time change event. 150 struct EventTime { 151 static constexpr uptr kUnusedBits = 37; 152 static_assert(kUnusedBits + sizeof(Sid) * kByteBits + kEpochBits + 5 == 64, 153 "unused bits in EventTime"); 154 155 u64 is_access : 1; // = 0 156 u64 is_func : 1; // = 0 157 EventType type : 3; // = EventType::kTime 158 u64 sid : sizeof(Sid) * kByteBits; 159 u64 epoch : kEpochBits; 160 u64 _ : kUnusedBits; 161 }; 162 static_assert(sizeof(EventTime) == 8, "bad EventTime size"); 163 164 struct Trace; 165 166 struct TraceHeader { 167 Trace* trace = nullptr; // back-pointer to Trace containing this part 168 INode trace_parts; // in Trace::parts 169 INode global; // in Contex::trace_part_recycle 170 }; 171 172 struct TracePart : TraceHeader { 173 // There are a lot of goroutines in Go, so we use smaller parts. 174 static constexpr uptr kByteSize = (SANITIZER_GO ? 128 : 256) << 10; 175 static constexpr uptr kSize = 176 (kByteSize - sizeof(TraceHeader)) / sizeof(Event); 177 // TraceAcquire does a fast event pointer overflow check by comparing 178 // pointer into TracePart::events with kAlignment mask. Since TracePart's 179 // are allocated page-aligned, this check detects end of the array 180 // (it also have false positives in the middle that are filtered separately). 181 // This also requires events to be the last field. 182 static constexpr uptr kAlignment = 0xff0; 183 Event events[kSize]; 184 185 TracePart() {} 186 }; 187 static_assert(sizeof(TracePart) == TracePart::kByteSize, "bad TracePart size"); 188 189 struct Trace { 190 Mutex mtx; 191 IList<TraceHeader, &TraceHeader::trace_parts, TracePart> parts; 192 // First node non-queued into ctx->trace_part_recycle. 193 TracePart* local_head; 194 // Final position in the last part for finished threads. 195 Event* final_pos = nullptr; 196 // Number of trace parts allocated on behalf of this trace specifically. 197 // Total number of parts in this trace can be larger if we retake some 198 // parts from other traces. 199 uptr parts_allocated = 0; 200 201 Trace() : mtx(MutexTypeTrace) {} 202 203 // We need at least 3 parts per thread, because we want to keep at last 204 // 2 parts per thread that are not queued into ctx->trace_part_recycle 205 // (the current one being filled and one full part that ensures that 206 // we always have at least one part worth of previous memory accesses). 207 static constexpr uptr kMinParts = 3; 208 209 static constexpr uptr kFinishedThreadLo = 16; 210 static constexpr uptr kFinishedThreadHi = 64; 211 }; 212 213 } // namespace __tsan 214 215 #endif // TSAN_TRACE_H 216
Indexes created Sat Aug 01 00:24:56 UTC 2026