1 //===-- PerfJITEventListener.cpp - Tell Linux's perf about JITted code ----===//
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
7 //===----------------------------------------------------------------------===//
9 // This file defines a JITEventListener object that tells perf about JITted
10 // functions, including source line information.
12 // Documentation for perf jit integration is available at:
13 // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jitdump-specification.txt
14 // https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Documentation/jit-interface.txt
16 //===----------------------------------------------------------------------===//
18 #include "llvm/ADT/Twine.h"
19 #include "llvm/Config/config.h"
20 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
21 #include "llvm/ExecutionEngine/JITEventListener.h"
22 #include "llvm/Object/ObjectFile.h"
23 #include "llvm/Object/SymbolSize.h"
24 #include "llvm/Support/Debug.h"
25 #include "llvm/Support/Errno.h"
26 #include "llvm/Support/FileSystem.h"
27 #include "llvm/Support/ManagedStatic.h"
28 #include "llvm/Support/MemoryBuffer.h"
29 #include "llvm/Support/Mutex.h"
30 #include "llvm/Support/Path.h"
31 #include "llvm/Support/Process.h"
32 #include "llvm/Support/Threading.h"
33 #include "llvm/Support/raw_ostream.h"
36 #include <sys/mman.h> // mmap()
37 #include <sys/types.h> // getpid()
38 #include <time.h> // clock_gettime(), time(), localtime_r() */
39 #include <unistd.h> // for getpid(), read(), close()
42 using namespace llvm::object;
43 typedef DILineInfoSpecifier::FileLineInfoKind FileLineInfoKind;
47 // language identifier (XXX: should we generate something better from debug
49 #define JIT_LANG "llvm-IR"
50 #define LLVM_PERF_JIT_MAGIC \
51 ((uint32_t)'J' << 24 | (uint32_t)'i' << 16 | (uint32_t)'T' << 8 | \
53 #define LLVM_PERF_JIT_VERSION 1
55 // bit 0: set if the jitdump file is using an architecture-specific timestamp
57 #define JITDUMP_FLAGS_ARCH_TIMESTAMP (1ULL << 0)
59 struct LLVMPerfJitHeader;
61 class PerfJITEventListener : public JITEventListener {
63 PerfJITEventListener();
64 ~PerfJITEventListener() {
69 void notifyObjectLoaded(ObjectKey K, const ObjectFile &Obj,
70 const RuntimeDyld::LoadedObjectInfo &L) override;
71 void notifyFreeingObject(ObjectKey K) override;
74 bool InitDebuggingDir();
77 static bool FillMachine(LLVMPerfJitHeader &hdr);
79 void NotifyCode(Expected<llvm::StringRef> &Symbol, uint64_t CodeAddr,
81 void NotifyDebug(uint64_t CodeAddr, DILineInfoTable Lines);
86 // base directory for output data
89 // output data stream, closed via Dumpstream
93 std::unique_ptr<raw_fd_ostream> Dumpstream;
95 // prevent concurrent dumps from messing up the output file
99 void *MarkerAddr = NULL;
101 // perf support ready
102 bool SuccessfullyInitialized = false;
104 // identifier for functions, primarily to identify when moving them around
105 uint64_t CodeGeneration = 1;
108 // The following are POD struct definitions from the perf jit specification
110 enum LLVMPerfJitRecordType {
112 JIT_CODE_MOVE = 1, // not emitted, code isn't moved
113 JIT_CODE_DEBUG_INFO = 2,
114 JIT_CODE_CLOSE = 3, // not emitted, unnecessary
115 JIT_CODE_UNWINDING_INFO = 4, // not emitted
120 struct LLVMPerfJitHeader {
121 uint32_t Magic; // characters "JiTD"
122 uint32_t Version; // header version
123 uint32_t TotalSize; // total size of header
124 uint32_t ElfMach; // elf mach target
125 uint32_t Pad1; // reserved
127 uint64_t Timestamp; // timestamp
128 uint64_t Flags; // flags
131 // record prefix (mandatory in each record)
132 struct LLVMPerfJitRecordPrefix {
133 uint32_t Id; // record type identifier
138 struct LLVMPerfJitRecordCodeLoad {
139 LLVMPerfJitRecordPrefix Prefix;
149 struct LLVMPerfJitDebugEntry {
151 int Lineno; // source line number starting at 1
152 int Discrim; // column discriminator, 0 is default
153 // followed by null terminated filename, \xff\0 if same as previous entry
156 struct LLVMPerfJitRecordDebugInfo {
157 LLVMPerfJitRecordPrefix Prefix;
161 // followed by NrEntry LLVMPerfJitDebugEntry records
164 static inline uint64_t timespec_to_ns(const struct timespec *ts) {
165 const uint64_t NanoSecPerSec = 1000000000;
166 return ((uint64_t)ts->tv_sec * NanoSecPerSec) + ts->tv_nsec;
169 static inline uint64_t perf_get_timestamp(void) {
173 ret = clock_gettime(CLOCK_MONOTONIC, &ts);
177 return timespec_to_ns(&ts);
180 PerfJITEventListener::PerfJITEventListener() : Pid(::getpid()) {
181 // check if clock-source is supported
182 if (!perf_get_timestamp()) {
183 errs() << "kernel does not support CLOCK_MONOTONIC\n";
187 if (!InitDebuggingDir()) {
188 errs() << "could not initialize debugging directory\n";
192 std::string Filename;
193 raw_string_ostream FilenameBuf(Filename);
194 FilenameBuf << JitPath << "/jit-" << Pid << ".dump";
196 // Need to open ourselves, because we need to hand the FD to OpenMarker() and
197 // raw_fd_ostream doesn't expose the FD.
198 using sys::fs::openFileForWrite;
200 openFileForReadWrite(FilenameBuf.str(), DumpFd,
201 sys::fs::CD_CreateNew, sys::fs::OF_None)) {
202 errs() << "could not open JIT dump file " << FilenameBuf.str() << ": "
203 << EC.message() << "\n";
207 Dumpstream = std::make_unique<raw_fd_ostream>(DumpFd, true);
209 LLVMPerfJitHeader Header = {0};
210 if (!FillMachine(Header))
213 // signal this process emits JIT information
217 // emit dumpstream header
218 Header.Magic = LLVM_PERF_JIT_MAGIC;
219 Header.Version = LLVM_PERF_JIT_VERSION;
220 Header.TotalSize = sizeof(Header);
222 Header.Timestamp = perf_get_timestamp();
223 Dumpstream->write(reinterpret_cast<const char *>(&Header), sizeof(Header));
225 // Everything initialized, can do profiling now.
226 if (!Dumpstream->has_error())
227 SuccessfullyInitialized = true;
230 void PerfJITEventListener::notifyObjectLoaded(
231 ObjectKey K, const ObjectFile &Obj,
232 const RuntimeDyld::LoadedObjectInfo &L) {
234 if (!SuccessfullyInitialized)
237 OwningBinary<ObjectFile> DebugObjOwner = L.getObjectForDebug(Obj);
238 const ObjectFile &DebugObj = *DebugObjOwner.getBinary();
240 // Get the address of the object image for use as a unique identifier
241 std::unique_ptr<DIContext> Context = DWARFContext::create(DebugObj);
243 // Use symbol info to iterate over functions in the object.
244 for (const std::pair<SymbolRef, uint64_t> &P : computeSymbolSizes(DebugObj)) {
245 SymbolRef Sym = P.first;
246 std::string SourceFileName;
248 Expected<SymbolRef::Type> SymTypeOrErr = Sym.getType();
250 // There's not much we can with errors here
251 consumeError(SymTypeOrErr.takeError());
254 SymbolRef::Type SymType = *SymTypeOrErr;
255 if (SymType != SymbolRef::ST_Function)
258 Expected<StringRef> Name = Sym.getName();
260 consumeError(Name.takeError());
264 Expected<uint64_t> AddrOrErr = Sym.getAddress();
266 consumeError(AddrOrErr.takeError());
269 uint64_t Size = P.second;
270 object::SectionedAddress Address;
271 Address.Address = *AddrOrErr;
273 uint64_t SectionIndex = object::SectionedAddress::UndefSection;
274 if (auto SectOrErr = Sym.getSection())
275 if (*SectOrErr != Obj.section_end())
276 SectionIndex = SectOrErr.get()->getIndex();
278 // According to spec debugging info has to come before loading the
279 // corresonding code load.
280 DILineInfoTable Lines = Context->getLineInfoForAddressRange(
281 {*AddrOrErr, SectionIndex}, Size, FileLineInfoKind::AbsoluteFilePath);
283 NotifyDebug(*AddrOrErr, Lines);
284 NotifyCode(Name, *AddrOrErr, Size);
290 void PerfJITEventListener::notifyFreeingObject(ObjectKey K) {
291 // perf currently doesn't have an interface for unloading. But munmap()ing the
292 // code section does, so that's ok.
295 bool PerfJITEventListener::InitDebuggingDir() {
298 char TimeBuffer[sizeof("YYYYMMDD")];
299 SmallString<64> Path;
301 // search for location to dump data to
302 if (const char *BaseDir = getenv("JITDUMPDIR"))
303 Path.append(BaseDir);
304 else if (!sys::path::home_directory(Path))
307 // create debug directory
308 Path += "/.debug/jit/";
309 if (auto EC = sys::fs::create_directories(Path)) {
310 errs() << "could not create jit cache directory " << Path << ": "
311 << EC.message() << "\n";
315 // create unique directory for dump data related to this process
317 localtime_r(&Time, &LocalTime);
318 strftime(TimeBuffer, sizeof(TimeBuffer), "%Y%m%d", &LocalTime);
319 Path += JIT_LANG "-jit-";
322 SmallString<128> UniqueDebugDir;
324 using sys::fs::createUniqueDirectory;
325 if (auto EC = createUniqueDirectory(Path, UniqueDebugDir)) {
326 errs() << "could not create unique jit cache directory " << UniqueDebugDir
327 << ": " << EC.message() << "\n";
331 JitPath = UniqueDebugDir.str();
336 bool PerfJITEventListener::OpenMarker() {
337 // We mmap the jitdump to create an MMAP RECORD in perf.data file. The mmap
338 // is captured either live (perf record running when we mmap) or in deferred
339 // mode, via /proc/PID/maps. The MMAP record is used as a marker of a jitdump
340 // file for more meta data info about the jitted code. Perf report/annotate
341 // detect this special filename and process the jitdump file.
343 // Mapping must be PROT_EXEC to ensure it is captured by perf record
344 // even when not using -d option.
345 MarkerAddr = ::mmap(NULL, sys::Process::getPageSizeEstimate(),
346 PROT_READ | PROT_EXEC, MAP_PRIVATE, DumpFd, 0);
348 if (MarkerAddr == MAP_FAILED) {
349 errs() << "could not mmap JIT marker\n";
355 void PerfJITEventListener::CloseMarker() {
359 munmap(MarkerAddr, sys::Process::getPageSizeEstimate());
360 MarkerAddr = nullptr;
363 bool PerfJITEventListener::FillMachine(LLVMPerfJitHeader &hdr) {
370 size_t RequiredMemory = sizeof(id) + sizeof(info);
372 ErrorOr<std::unique_ptr<MemoryBuffer>> MB =
373 MemoryBuffer::getFileSlice("/proc/self/exe",
377 // This'll not guarantee that enough data was actually read from the
378 // underlying file. Instead the trailing part of the buffer would be
379 // zeroed. Given the ELF signature check below that seems ok though,
380 // it's unlikely that the file ends just after that, and the
381 // consequence would just be that perf wouldn't recognize the
383 if (auto EC = MB.getError()) {
384 errs() << "could not open /proc/self/exe: " << EC.message() << "\n";
388 memcpy(&id, (*MB)->getBufferStart(), sizeof(id));
389 memcpy(&info, (*MB)->getBufferStart() + sizeof(id), sizeof(info));
391 // check ELF signature
392 if (id[0] != 0x7f || id[1] != 'E' || id[2] != 'L' || id[3] != 'F') {
393 errs() << "invalid elf signature\n";
397 hdr.ElfMach = info.e_machine;
402 void PerfJITEventListener::NotifyCode(Expected<llvm::StringRef> &Symbol,
403 uint64_t CodeAddr, uint64_t CodeSize) {
404 assert(SuccessfullyInitialized);
406 // 0 length functions can't have samples.
410 LLVMPerfJitRecordCodeLoad rec;
411 rec.Prefix.Id = JIT_CODE_LOAD;
412 rec.Prefix.TotalSize = sizeof(rec) + // debug record itself
413 Symbol->size() + 1 + // symbol name
414 CodeSize; // and code
415 rec.Prefix.Timestamp = perf_get_timestamp();
417 rec.CodeSize = CodeSize;
419 rec.CodeAddr = CodeAddr;
421 rec.Tid = get_threadid();
423 // avoid interspersing output
424 std::lock_guard<sys::Mutex> Guard(Mutex);
426 rec.CodeIndex = CodeGeneration++; // under lock!
428 Dumpstream->write(reinterpret_cast<const char *>(&rec), sizeof(rec));
429 Dumpstream->write(Symbol->data(), Symbol->size() + 1);
430 Dumpstream->write(reinterpret_cast<const char *>(CodeAddr), CodeSize);
433 void PerfJITEventListener::NotifyDebug(uint64_t CodeAddr,
434 DILineInfoTable Lines) {
435 assert(SuccessfullyInitialized);
437 // Didn't get useful debug info.
441 LLVMPerfJitRecordDebugInfo rec;
442 rec.Prefix.Id = JIT_CODE_DEBUG_INFO;
443 rec.Prefix.TotalSize = sizeof(rec); // will be increased further
444 rec.Prefix.Timestamp = perf_get_timestamp();
445 rec.CodeAddr = CodeAddr;
446 rec.NrEntry = Lines.size();
448 // compute total size size of record (variable due to filenames)
449 DILineInfoTable::iterator Begin = Lines.begin();
450 DILineInfoTable::iterator End = Lines.end();
451 for (DILineInfoTable::iterator It = Begin; It != End; ++It) {
452 DILineInfo &line = It->second;
453 rec.Prefix.TotalSize += sizeof(LLVMPerfJitDebugEntry);
454 rec.Prefix.TotalSize += line.FileName.size() + 1;
457 // The debug_entry describes the source line information. It is defined as
459 // * uint64_t code_addr: address of function for which the debug information
461 // * uint32_t line : source file line number (starting at 1)
462 // * uint32_t discrim : column discriminator, 0 is default
463 // * char name[n] : source file name in ASCII, including null termination
465 // avoid interspersing output
466 std::lock_guard<sys::Mutex> Guard(Mutex);
468 Dumpstream->write(reinterpret_cast<const char *>(&rec), sizeof(rec));
470 for (DILineInfoTable::iterator It = Begin; It != End; ++It) {
471 LLVMPerfJitDebugEntry LineInfo;
472 DILineInfo &Line = It->second;
474 LineInfo.Addr = It->first;
475 // The function re-created by perf is preceded by a elf
476 // header. Need to adjust for that, otherwise the results are
478 LineInfo.Addr += 0x40;
479 LineInfo.Lineno = Line.Line;
480 LineInfo.Discrim = Line.Discriminator;
482 Dumpstream->write(reinterpret_cast<const char *>(&LineInfo),
484 Dumpstream->write(Line.FileName.c_str(), Line.FileName.size() + 1);
488 // There should be only a single event listener per process, otherwise perf gets
490 llvm::ManagedStatic<PerfJITEventListener> PerfListener;
492 } // end anonymous namespace
495 JITEventListener *JITEventListener::createPerfJITEventListener() {
496 return &*PerfListener;
501 LLVMJITEventListenerRef LLVMCreatePerfJITEventListener(void)
503 return wrap(JITEventListener::createPerfJITEventListener());