1 //===-- xray_profile_collector.cpp -----------------------------*- 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 XRay, a dynamic runtime instrumentation system.
10 //
11 // This implements the interface for the profileCollectorService.
12 //
13 //===----------------------------------------------------------------------===//
14 #include "xray_profile_collector.h"
15 #include "sanitizer_common/sanitizer_common.h"
16 #include "xray_allocator.h"
17 #include "xray_defs.h"
18 #include "xray_profiling_flags.h"
19 #include "xray_segmented_array.h"
20 #include <memory>
21 #include <pthread.h>
22 #include <utility>
23
24 namespace __xray {
25 namespace profileCollectorService {
26
27 namespace {
28
29 SpinMutex GlobalMutex;
30 struct ThreadTrie {
31 tid_t TId;
32 alignas(FunctionCallTrie) std::byte TrieStorage[sizeof(FunctionCallTrie)];
33 };
34
35 struct ProfileBuffer {
36 void *Data;
37 size_t Size;
38 };
39
40 // Current version of the profile format.
41 constexpr u64 XRayProfilingVersion = 0x20180424;
42
43 // Identifier for XRay profiling files 'xrayprof' in hex.
44 constexpr u64 XRayMagicBytes = 0x7872617970726f66;
45
46 struct XRayProfilingFileHeader {
47 const u64 MagicBytes = XRayMagicBytes;
48 const u64 Version = XRayProfilingVersion;
49 u64 Timestamp = 0; // System time in nanoseconds.
50 u64 PID = 0; // Process ID.
51 };
52
53 struct BlockHeader {
54 u32 BlockSize;
55 u32 BlockNum;
56 u64 ThreadId;
57 };
58
59 struct ThreadData {
60 BufferQueue *BQ;
61 FunctionCallTrie::Allocators::Buffers Buffers;
62 FunctionCallTrie::Allocators Allocators;
63 FunctionCallTrie FCT;
64 tid_t TId;
65 };
66
67 using ThreadDataArray = Array<ThreadData>;
68 using ThreadDataAllocator = ThreadDataArray::AllocatorType;
69
70 // We use a separate buffer queue for the backing store for the allocator used
71 // by the ThreadData array. This lets us host the buffers, allocators, and tries
72 // associated with a thread by moving the data into the array instead of
73 // attempting to copy the data to a separately backed set of tries.
74 alignas(BufferQueue) static std::byte BufferQueueStorage[sizeof(BufferQueue)];
75 static BufferQueue *BQ = nullptr;
76 static BufferQueue::Buffer Buffer;
77 alignas(ThreadDataAllocator) static std::byte
78 ThreadDataAllocatorStorage[sizeof(ThreadDataAllocator)];
79 alignas(ThreadDataArray) static std::byte
80 ThreadDataArrayStorage[sizeof(ThreadDataArray)];
81
82 static ThreadDataAllocator *TDAllocator = nullptr;
83 static ThreadDataArray *TDArray = nullptr;
84
85 using ProfileBufferArray = Array<ProfileBuffer>;
86 using ProfileBufferArrayAllocator = typename ProfileBufferArray::AllocatorType;
87
88 // These need to be global aligned storage to avoid dynamic initialization. We
89 // need these to be aligned to allow us to placement new objects into the
90 // storage, and have pointers to those objects be appropriately aligned.
91 alignas(ProfileBufferArray) static std::byte
92 ProfileBuffersStorage[sizeof(ProfileBufferArray)];
93 alignas(ProfileBufferArrayAllocator) static std::byte
94 ProfileBufferArrayAllocatorStorage[sizeof(ProfileBufferArrayAllocator)];
95
96 static ProfileBufferArrayAllocator *ProfileBuffersAllocator = nullptr;
97 static ProfileBufferArray *ProfileBuffers = nullptr;
98
99 // Use a global flag to determine whether the collector implementation has been
100 // initialized.
101 static atomic_uint8_t CollectorInitialized{0};
102
103 } // namespace
104
post(BufferQueue * Q,FunctionCallTrie && T,FunctionCallTrie::Allocators && A,FunctionCallTrie::Allocators::Buffers && B,tid_t TId)105 void post(BufferQueue *Q, FunctionCallTrie &&T,
106 FunctionCallTrie::Allocators &&A,
107 FunctionCallTrie::Allocators::Buffers &&B,
108 tid_t TId) XRAY_NEVER_INSTRUMENT {
109 DCHECK_NE(Q, nullptr);
110
111 // Bail out early if the collector has not been initialized.
112 if (!atomic_load(&CollectorInitialized, memory_order_acquire)) {
113 T.~FunctionCallTrie();
114 A.~Allocators();
115 Q->releaseBuffer(B.NodeBuffer);
116 Q->releaseBuffer(B.RootsBuffer);
117 Q->releaseBuffer(B.ShadowStackBuffer);
118 Q->releaseBuffer(B.NodeIdPairBuffer);
119 B.~Buffers();
120 return;
121 }
122
123 {
124 SpinMutexLock Lock(&GlobalMutex);
125 DCHECK_NE(TDAllocator, nullptr);
126 DCHECK_NE(TDArray, nullptr);
127
128 if (TDArray->AppendEmplace(Q, std::move(B), std::move(A), std::move(T),
129 TId) == nullptr) {
130 // If we fail to add the data to the array, we should destroy the objects
131 // handed us.
132 T.~FunctionCallTrie();
133 A.~Allocators();
134 Q->releaseBuffer(B.NodeBuffer);
135 Q->releaseBuffer(B.RootsBuffer);
136 Q->releaseBuffer(B.ShadowStackBuffer);
137 Q->releaseBuffer(B.NodeIdPairBuffer);
138 B.~Buffers();
139 }
140 }
141 }
142
143 // A PathArray represents the function id's representing a stack trace. In this
144 // context a path is almost always represented from the leaf function in a call
145 // stack to a root of the call trie.
146 using PathArray = Array<int32_t>;
147
148 struct ProfileRecord {
149 using PathAllocator = typename PathArray::AllocatorType;
150
151 // The Path in this record is the function id's from the leaf to the root of
152 // the function call stack as represented from a FunctionCallTrie.
153 PathArray Path;
154 const FunctionCallTrie::Node *Node;
155 };
156
157 namespace {
158
159 using ProfileRecordArray = Array<ProfileRecord>;
160
161 // Walk a depth-first traversal of each root of the FunctionCallTrie to generate
162 // the path(s) and the data associated with the path.
163 static void
populateRecords(ProfileRecordArray & PRs,ProfileRecord::PathAllocator & PA,const FunctionCallTrie & Trie)164 populateRecords(ProfileRecordArray &PRs, ProfileRecord::PathAllocator &PA,
165 const FunctionCallTrie &Trie) XRAY_NEVER_INSTRUMENT {
166 using StackArray = Array<const FunctionCallTrie::Node *>;
167 using StackAllocator = typename StackArray::AllocatorType;
168 StackAllocator StackAlloc(profilingFlags()->stack_allocator_max);
169 StackArray DFSStack(StackAlloc);
170 for (const auto *R : Trie.getRoots()) {
171 DFSStack.Append(R);
172 while (!DFSStack.empty()) {
173 auto *Node = DFSStack.back();
174 DFSStack.trim(1);
175 if (Node == nullptr)
176 continue;
177 auto Record = PRs.AppendEmplace(PathArray{PA}, Node);
178 if (Record == nullptr)
179 return;
180 DCHECK_NE(Record, nullptr);
181
182 // Traverse the Node's parents and as we're doing so, get the FIds in
183 // the order they appear.
184 for (auto N = Node; N != nullptr; N = N->Parent)
185 Record->Path.Append(N->FId);
186 DCHECK(!Record->Path.empty());
187
188 for (const auto C : Node->Callees)
189 DFSStack.Append(C.NodePtr);
190 }
191 }
192 }
193
serializeRecords(ProfileBuffer * Buffer,const BlockHeader & Header,const ProfileRecordArray & ProfileRecords)194 static void serializeRecords(ProfileBuffer *Buffer, const BlockHeader &Header,
195 const ProfileRecordArray &ProfileRecords)
196 XRAY_NEVER_INSTRUMENT {
197 auto NextPtr = static_cast<uint8_t *>(
198 internal_memcpy(Buffer->Data, &Header, sizeof(Header))) +
199 sizeof(Header);
200 for (const auto &Record : ProfileRecords) {
201 // List of IDs follow:
202 for (const auto FId : Record.Path)
203 NextPtr =
204 static_cast<uint8_t *>(internal_memcpy(NextPtr, &FId, sizeof(FId))) +
205 sizeof(FId);
206
207 // Add the sentinel here.
208 constexpr int32_t SentinelFId = 0;
209 NextPtr = static_cast<uint8_t *>(
210 internal_memset(NextPtr, SentinelFId, sizeof(SentinelFId))) +
211 sizeof(SentinelFId);
212
213 // Add the node data here.
214 NextPtr =
215 static_cast<uint8_t *>(internal_memcpy(
216 NextPtr, &Record.Node->CallCount, sizeof(Record.Node->CallCount))) +
217 sizeof(Record.Node->CallCount);
218 NextPtr = static_cast<uint8_t *>(
219 internal_memcpy(NextPtr, &Record.Node->CumulativeLocalTime,
220 sizeof(Record.Node->CumulativeLocalTime))) +
221 sizeof(Record.Node->CumulativeLocalTime);
222 }
223
224 DCHECK_EQ(NextPtr - static_cast<uint8_t *>(Buffer->Data), Buffer->Size);
225 }
226
227 } // namespace
228
serialize()229 void serialize() XRAY_NEVER_INSTRUMENT {
230 if (!atomic_load(&CollectorInitialized, memory_order_acquire))
231 return;
232
233 SpinMutexLock Lock(&GlobalMutex);
234
235 // Clear out the global ProfileBuffers, if it's not empty.
236 for (auto &B : *ProfileBuffers)
237 deallocateBuffer(reinterpret_cast<unsigned char *>(B.Data), B.Size);
238 ProfileBuffers->trim(ProfileBuffers->size());
239
240 DCHECK_NE(TDArray, nullptr);
241 if (TDArray->empty())
242 return;
243
244 // Then repopulate the global ProfileBuffers.
245 u32 I = 0;
246 auto MaxSize = profilingFlags()->global_allocator_max;
247 auto ProfileArena = allocateBuffer(MaxSize);
248 if (ProfileArena == nullptr)
249 return;
250
251 auto ProfileArenaCleanup = at_scope_exit(
252 [&]() XRAY_NEVER_INSTRUMENT { deallocateBuffer(ProfileArena, MaxSize); });
253
254 auto PathArena = allocateBuffer(profilingFlags()->global_allocator_max);
255 if (PathArena == nullptr)
256 return;
257
258 auto PathArenaCleanup = at_scope_exit(
259 [&]() XRAY_NEVER_INSTRUMENT { deallocateBuffer(PathArena, MaxSize); });
260
261 for (const auto &ThreadTrie : *TDArray) {
262 using ProfileRecordAllocator = typename ProfileRecordArray::AllocatorType;
263 ProfileRecordAllocator PRAlloc(ProfileArena,
264 profilingFlags()->global_allocator_max);
265 ProfileRecord::PathAllocator PathAlloc(
266 PathArena, profilingFlags()->global_allocator_max);
267 ProfileRecordArray ProfileRecords(PRAlloc);
268
269 // First, we want to compute the amount of space we're going to need. We'll
270 // use a local allocator and an __xray::Array<...> to store the intermediary
271 // data, then compute the size as we're going along. Then we'll allocate the
272 // contiguous space to contain the thread buffer data.
273 if (ThreadTrie.FCT.getRoots().empty())
274 continue;
275
276 populateRecords(ProfileRecords, PathAlloc, ThreadTrie.FCT);
277 DCHECK(!ThreadTrie.FCT.getRoots().empty());
278 DCHECK(!ProfileRecords.empty());
279
280 // Go through each record, to compute the sizes.
281 //
282 // header size = block size (4 bytes)
283 // + block number (4 bytes)
284 // + thread id (8 bytes)
285 // record size = path ids (4 bytes * number of ids + sentinel 4 bytes)
286 // + call count (8 bytes)
287 // + local time (8 bytes)
288 // + end of record (8 bytes)
289 u32 CumulativeSizes = 0;
290 for (const auto &Record : ProfileRecords)
291 CumulativeSizes += 20 + (4 * Record.Path.size());
292
293 BlockHeader Header{16 + CumulativeSizes, I++, ThreadTrie.TId};
294 auto B = ProfileBuffers->Append({});
295 B->Size = sizeof(Header) + CumulativeSizes;
296 B->Data = allocateBuffer(B->Size);
297 DCHECK_NE(B->Data, nullptr);
298 serializeRecords(B, Header, ProfileRecords);
299 }
300 }
301
reset()302 void reset() XRAY_NEVER_INSTRUMENT {
303 atomic_store(&CollectorInitialized, 0, memory_order_release);
304 SpinMutexLock Lock(&GlobalMutex);
305
306 if (ProfileBuffers != nullptr) {
307 // Clear out the profile buffers that have been serialized.
308 for (auto &B : *ProfileBuffers)
309 deallocateBuffer(reinterpret_cast<uint8_t *>(B.Data), B.Size);
310 ProfileBuffers->trim(ProfileBuffers->size());
311 ProfileBuffers = nullptr;
312 }
313
314 if (TDArray != nullptr) {
315 // Release the resources as required.
316 for (auto &TD : *TDArray) {
317 TD.BQ->releaseBuffer(TD.Buffers.NodeBuffer);
318 TD.BQ->releaseBuffer(TD.Buffers.RootsBuffer);
319 TD.BQ->releaseBuffer(TD.Buffers.ShadowStackBuffer);
320 TD.BQ->releaseBuffer(TD.Buffers.NodeIdPairBuffer);
321 }
322 // We don't bother destroying the array here because we've already
323 // potentially freed the backing store for the array. Instead we're going to
324 // reset the pointer to nullptr, and re-use the storage later instead
325 // (placement-new'ing into the storage as-is).
326 TDArray = nullptr;
327 }
328
329 if (TDAllocator != nullptr) {
330 TDAllocator->~Allocator();
331 TDAllocator = nullptr;
332 }
333
334 if (Buffer.Data != nullptr) {
335 BQ->releaseBuffer(Buffer);
336 }
337
338 if (BQ == nullptr) {
339 bool Success = false;
340 new (&BufferQueueStorage)
341 BufferQueue(profilingFlags()->global_allocator_max, 1, Success);
342 if (!Success)
343 return;
344 BQ = reinterpret_cast<BufferQueue *>(&BufferQueueStorage);
345 } else {
346 BQ->finalize();
347
348 if (BQ->init(profilingFlags()->global_allocator_max, 1) !=
349 BufferQueue::ErrorCode::Ok)
350 return;
351 }
352
353 if (BQ->getBuffer(Buffer) != BufferQueue::ErrorCode::Ok)
354 return;
355
356 new (&ProfileBufferArrayAllocatorStorage)
357 ProfileBufferArrayAllocator(profilingFlags()->global_allocator_max);
358 ProfileBuffersAllocator = reinterpret_cast<ProfileBufferArrayAllocator *>(
359 &ProfileBufferArrayAllocatorStorage);
360
361 new (&ProfileBuffersStorage) ProfileBufferArray(*ProfileBuffersAllocator);
362 ProfileBuffers =
363 reinterpret_cast<ProfileBufferArray *>(&ProfileBuffersStorage);
364
365 new (&ThreadDataAllocatorStorage)
366 ThreadDataAllocator(Buffer.Data, Buffer.Size);
367 TDAllocator =
368 reinterpret_cast<ThreadDataAllocator *>(&ThreadDataAllocatorStorage);
369 new (&ThreadDataArrayStorage) ThreadDataArray(*TDAllocator);
370 TDArray = reinterpret_cast<ThreadDataArray *>(&ThreadDataArrayStorage);
371
372 atomic_store(&CollectorInitialized, 1, memory_order_release);
373 }
374
nextBuffer(XRayBuffer B)375 XRayBuffer nextBuffer(XRayBuffer B) XRAY_NEVER_INSTRUMENT {
376 SpinMutexLock Lock(&GlobalMutex);
377
378 if (ProfileBuffers == nullptr || ProfileBuffers->size() == 0)
379 return {nullptr, 0};
380
381 static pthread_once_t Once = PTHREAD_ONCE_INIT;
382 alignas(XRayProfilingFileHeader) static std::byte
383 FileHeaderStorage[sizeof(XRayProfilingFileHeader)];
384 pthread_once(
385 &Once, +[]() XRAY_NEVER_INSTRUMENT {
386 new (&FileHeaderStorage) XRayProfilingFileHeader{};
387 });
388
389 if (UNLIKELY(B.Data == nullptr)) {
390 // The first buffer should always contain the file header information.
391 auto &FileHeader =
392 *reinterpret_cast<XRayProfilingFileHeader *>(&FileHeaderStorage);
393 FileHeader.Timestamp = NanoTime();
394 FileHeader.PID = internal_getpid();
395 return {&FileHeaderStorage, sizeof(XRayProfilingFileHeader)};
396 }
397
398 if (UNLIKELY(B.Data == &FileHeaderStorage))
399 return {(*ProfileBuffers)[0].Data, (*ProfileBuffers)[0].Size};
400
401 BlockHeader Header;
402 internal_memcpy(&Header, B.Data, sizeof(BlockHeader));
403 auto NextBlock = Header.BlockNum + 1;
404 if (NextBlock < ProfileBuffers->size())
405 return {(*ProfileBuffers)[NextBlock].Data,
406 (*ProfileBuffers)[NextBlock].Size};
407 return {nullptr, 0};
408 }
409
410 } // namespace profileCollectorService
411 } // namespace __xray
412