1 //===------ MachOPlatform.cpp - Utilities for executing MachO in Orc ------===//
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 #include "llvm/ExecutionEngine/Orc/MachOPlatform.h"
10 
11 #include "llvm/BinaryFormat/MachO.h"
12 #include "llvm/ExecutionEngine/Orc/DebugUtils.h"
13 #include "llvm/Support/BinaryByteStream.h"
14 #include "llvm/Support/Debug.h"
15 
16 #define DEBUG_TYPE "orc"
17 
18 namespace {
19 
20 struct objc_class;
21 struct objc_image_info;
22 struct objc_object;
23 struct objc_selector;
24 
25 using Class = objc_class *;
26 using id = objc_object *;
27 using SEL = objc_selector *;
28 
29 using ObjCMsgSendTy = id (*)(id, SEL, ...);
30 using ObjCReadClassPairTy = Class (*)(Class, const objc_image_info *);
31 using SelRegisterNameTy = SEL (*)(const char *);
32 
33 enum class ObjCRegistrationAPI { Uninitialized, Unavailable, Initialized };
34 
35 ObjCRegistrationAPI ObjCRegistrationAPIState =
36     ObjCRegistrationAPI::Uninitialized;
37 ObjCMsgSendTy objc_msgSend = nullptr;
38 ObjCReadClassPairTy objc_readClassPair = nullptr;
39 SelRegisterNameTy sel_registerName = nullptr;
40 
41 } // end anonymous namespace
42 
43 namespace llvm {
44 namespace orc {
45 
46 template <typename FnTy>
47 static Error setUpObjCRegAPIFunc(FnTy &Target, sys::DynamicLibrary &LibObjC,
48                                  const char *Name) {
49   if (void *Addr = LibObjC.getAddressOfSymbol(Name))
50     Target = reinterpret_cast<FnTy>(Addr);
51   else
52     return make_error<StringError>(
53         (Twine("Could not find address for ") + Name).str(),
54         inconvertibleErrorCode());
55   return Error::success();
56 }
57 
58 Error enableObjCRegistration(const char *PathToLibObjC) {
59   // If we've already tried to initialize then just bail out.
60   if (ObjCRegistrationAPIState != ObjCRegistrationAPI::Uninitialized)
61     return Error::success();
62 
63   ObjCRegistrationAPIState = ObjCRegistrationAPI::Unavailable;
64 
65   std::string ErrMsg;
66   auto LibObjC =
67       sys::DynamicLibrary::getPermanentLibrary(PathToLibObjC, &ErrMsg);
68 
69   if (!LibObjC.isValid())
70     return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
71 
72   if (auto Err = setUpObjCRegAPIFunc(objc_msgSend, LibObjC, "objc_msgSend"))
73     return Err;
74   if (auto Err = setUpObjCRegAPIFunc(objc_readClassPair, LibObjC,
75                                      "objc_readClassPair"))
76     return Err;
77   if (auto Err =
78           setUpObjCRegAPIFunc(sel_registerName, LibObjC, "sel_registerName"))
79     return Err;
80 
81   ObjCRegistrationAPIState = ObjCRegistrationAPI::Initialized;
82   return Error::success();
83 }
84 
85 bool objCRegistrationEnabled() {
86   return ObjCRegistrationAPIState == ObjCRegistrationAPI::Initialized;
87 }
88 
89 void MachOJITDylibInitializers::runModInits() const {
90   for (const auto &ModInit : ModInitSections) {
91     for (uint64_t I = 0; I != ModInit.NumPtrs; ++I) {
92       auto *InitializerAddr = jitTargetAddressToPointer<uintptr_t *>(
93           ModInit.Address + (I * sizeof(uintptr_t)));
94       auto *Initializer =
95           jitTargetAddressToFunction<void (*)()>(*InitializerAddr);
96       Initializer();
97     }
98   }
99 }
100 
101 void MachOJITDylibInitializers::registerObjCSelectors() const {
102   assert(objCRegistrationEnabled() && "ObjC registration not enabled.");
103 
104   for (const auto &ObjCSelRefs : ObjCSelRefsSections) {
105     for (uint64_t I = 0; I != ObjCSelRefs.NumPtrs; ++I) {
106       auto SelEntryAddr = ObjCSelRefs.Address + (I * sizeof(uintptr_t));
107       const auto *SelName =
108           *jitTargetAddressToPointer<const char **>(SelEntryAddr);
109       auto Sel = sel_registerName(SelName);
110       *jitTargetAddressToPointer<SEL *>(SelEntryAddr) = Sel;
111     }
112   }
113 }
114 
115 Error MachOJITDylibInitializers::registerObjCClasses() const {
116   assert(objCRegistrationEnabled() && "ObjC registration not enabled.");
117 
118   struct ObjCClassCompiled {
119     void *Metaclass;
120     void *Parent;
121     void *Cache1;
122     void *Cache2;
123     void *Data;
124   };
125 
126   auto *ImageInfo =
127       jitTargetAddressToPointer<const objc_image_info *>(ObjCImageInfoAddr);
128   auto ClassSelector = sel_registerName("class");
129 
130   for (const auto &ObjCClassList : ObjCClassListSections) {
131     for (uint64_t I = 0; I != ObjCClassList.NumPtrs; ++I) {
132       auto ClassPtrAddr = ObjCClassList.Address + (I * sizeof(uintptr_t));
133       auto Cls = *jitTargetAddressToPointer<Class *>(ClassPtrAddr);
134       auto *ClassCompiled =
135           *jitTargetAddressToPointer<ObjCClassCompiled **>(ClassPtrAddr);
136       objc_msgSend(reinterpret_cast<id>(ClassCompiled->Parent), ClassSelector);
137       auto Registered = objc_readClassPair(Cls, ImageInfo);
138 
139       // FIXME: Improve diagnostic by reporting the failed class's name.
140       if (Registered != Cls)
141         return make_error<StringError>("Unable to register Objective-C class",
142                                        inconvertibleErrorCode());
143     }
144   }
145   return Error::success();
146 }
147 
148 MachOPlatform::MachOPlatform(
149     ExecutionSession &ES, ObjectLinkingLayer &ObjLinkingLayer,
150     std::unique_ptr<MemoryBuffer> StandardSymbolsObject)
151     : ES(ES), ObjLinkingLayer(ObjLinkingLayer),
152       StandardSymbolsObject(std::move(StandardSymbolsObject)) {
153   ObjLinkingLayer.addPlugin(std::make_unique<InitScraperPlugin>(*this));
154 }
155 
156 Error MachOPlatform::setupJITDylib(JITDylib &JD) {
157   auto ObjBuffer = MemoryBuffer::getMemBuffer(
158       StandardSymbolsObject->getMemBufferRef(), false);
159   return ObjLinkingLayer.add(JD, std::move(ObjBuffer));
160 }
161 
162 Error MachOPlatform::notifyAdding(JITDylib &JD, const MaterializationUnit &MU) {
163   const auto &InitSym = MU.getInitializerSymbol();
164   if (!InitSym)
165     return Error::success();
166 
167   RegisteredInitSymbols[&JD].add(InitSym,
168                                  SymbolLookupFlags::WeaklyReferencedSymbol);
169   LLVM_DEBUG({
170     dbgs() << "MachOPlatform: Registered init symbol " << *InitSym << " for MU "
171            << MU.getName() << "\n";
172   });
173   return Error::success();
174 }
175 
176 Error MachOPlatform::notifyRemoving(JITDylib &JD, VModuleKey K) {
177   llvm_unreachable("Not supported yet");
178 }
179 
180 Expected<MachOPlatform::InitializerSequence>
181 MachOPlatform::getInitializerSequence(JITDylib &JD) {
182 
183   LLVM_DEBUG({
184     dbgs() << "MachOPlatform: Building initializer sequence for "
185            << JD.getName() << "\n";
186   });
187 
188   std::vector<std::shared_ptr<JITDylib>> DFSLinkOrder;
189 
190   while (true) {
191 
192     DenseMap<JITDylib *, SymbolLookupSet> NewInitSymbols;
193 
194     ES.runSessionLocked([&]() {
195       DFSLinkOrder = JD.getDFSLinkOrder();
196 
197       for (auto &InitJD : DFSLinkOrder) {
198         auto RISItr = RegisteredInitSymbols.find(InitJD.get());
199         if (RISItr != RegisteredInitSymbols.end()) {
200           NewInitSymbols[InitJD.get()] = std::move(RISItr->second);
201           RegisteredInitSymbols.erase(RISItr);
202         }
203       }
204     });
205 
206     if (NewInitSymbols.empty())
207       break;
208 
209     LLVM_DEBUG({
210       dbgs() << "MachOPlatform: Issuing lookups for new init symbols: "
211                 "(lookup may require multiple rounds)\n";
212       for (auto &KV : NewInitSymbols)
213         dbgs() << "  \"" << KV.first->getName() << "\": " << KV.second << "\n";
214     });
215 
216     // Outside the lock, issue the lookup.
217     if (auto R = lookupInitSymbols(JD.getExecutionSession(), NewInitSymbols))
218       ; // Nothing to do in the success case.
219     else
220       return R.takeError();
221   }
222 
223   LLVM_DEBUG({
224     dbgs() << "MachOPlatform: Init symbol lookup complete, building init "
225               "sequence\n";
226   });
227 
228   // Lock again to collect the initializers.
229   InitializerSequence FullInitSeq;
230   {
231     std::lock_guard<std::mutex> Lock(InitSeqsMutex);
232     for (auto &InitJD : reverse(DFSLinkOrder)) {
233       LLVM_DEBUG({
234         dbgs() << "MachOPlatform: Appending inits for \"" << InitJD->getName()
235                << "\" to sequence\n";
236       });
237       auto ISItr = InitSeqs.find(InitJD.get());
238       if (ISItr != InitSeqs.end()) {
239         FullInitSeq.emplace_back(InitJD.get(), std::move(ISItr->second));
240         InitSeqs.erase(ISItr);
241       }
242     }
243   }
244 
245   return FullInitSeq;
246 }
247 
248 Expected<MachOPlatform::DeinitializerSequence>
249 MachOPlatform::getDeinitializerSequence(JITDylib &JD) {
250   std::vector<std::shared_ptr<JITDylib>> DFSLinkOrder = JD.getDFSLinkOrder();
251 
252   DeinitializerSequence FullDeinitSeq;
253   {
254     std::lock_guard<std::mutex> Lock(InitSeqsMutex);
255     for (auto &DeinitJD : DFSLinkOrder) {
256       FullDeinitSeq.emplace_back(DeinitJD.get(), MachOJITDylibDeinitializers());
257     }
258   }
259 
260   return FullDeinitSeq;
261 }
262 
263 void MachOPlatform::registerInitInfo(
264     JITDylib &JD, JITTargetAddress ObjCImageInfoAddr,
265     MachOJITDylibInitializers::SectionExtent ModInits,
266     MachOJITDylibInitializers::SectionExtent ObjCSelRefs,
267     MachOJITDylibInitializers::SectionExtent ObjCClassList) {
268   std::lock_guard<std::mutex> Lock(InitSeqsMutex);
269 
270   auto &InitSeq = InitSeqs[&JD];
271 
272   InitSeq.setObjCImageInfoAddr(ObjCImageInfoAddr);
273 
274   if (ModInits.Address)
275     InitSeq.addModInitsSection(std::move(ModInits));
276 
277   if (ObjCSelRefs.Address)
278     InitSeq.addObjCSelRefsSection(std::move(ObjCSelRefs));
279 
280   if (ObjCClassList.Address)
281     InitSeq.addObjCClassListSection(std::move(ObjCClassList));
282 }
283 
284 static Expected<MachOJITDylibInitializers::SectionExtent>
285 getSectionExtent(jitlink::LinkGraph &G, StringRef SectionName) {
286   auto *Sec = G.findSectionByName(SectionName);
287   if (!Sec)
288     return MachOJITDylibInitializers::SectionExtent();
289   jitlink::SectionRange R(*Sec);
290   if (R.getSize() % G.getPointerSize() != 0)
291     return make_error<StringError>(SectionName + " section size is not a "
292                                                  "multiple of the pointer size",
293                                    inconvertibleErrorCode());
294   return MachOJITDylibInitializers::SectionExtent(
295       R.getStart(), R.getSize() / G.getPointerSize());
296 }
297 
298 void MachOPlatform::InitScraperPlugin::modifyPassConfig(
299     MaterializationResponsibility &MR, const Triple &TT,
300     jitlink::PassConfiguration &Config) {
301 
302   if (!MR.getInitializerSymbol())
303     return;
304 
305   Config.PrePrunePasses.push_back([this, &MR](jitlink::LinkGraph &G) -> Error {
306     JITLinkSymbolVector InitSectionSymbols;
307     preserveInitSectionIfPresent(InitSectionSymbols, G, "__mod_init_func");
308     preserveInitSectionIfPresent(InitSectionSymbols, G, "__objc_selrefs");
309     preserveInitSectionIfPresent(InitSectionSymbols, G, "__objc_classlist");
310 
311     if (!InitSectionSymbols.empty()) {
312       std::lock_guard<std::mutex> Lock(InitScraperMutex);
313       InitSymbolDeps[&MR] = std::move(InitSectionSymbols);
314     }
315 
316     if (auto Err = processObjCImageInfo(G, MR))
317       return Err;
318 
319     return Error::success();
320   });
321 
322   Config.PostFixupPasses.push_back([this, &JD = MR.getTargetJITDylib()](
323                                        jitlink::LinkGraph &G) -> Error {
324     MachOJITDylibInitializers::SectionExtent ModInits, ObjCSelRefs,
325         ObjCClassList;
326 
327     JITTargetAddress ObjCImageInfoAddr = 0;
328     if (auto *ObjCImageInfoSec = G.findSectionByName("__objc_image_info")) {
329       if (auto Addr = jitlink::SectionRange(*ObjCImageInfoSec).getStart())
330         ObjCImageInfoAddr = Addr;
331     }
332 
333     // Record __mod_init_func.
334     if (auto ModInitsOrErr = getSectionExtent(G, "__mod_init_func"))
335       ModInits = std::move(*ModInitsOrErr);
336     else
337       return ModInitsOrErr.takeError();
338 
339     // Record __objc_selrefs.
340     if (auto ObjCSelRefsOrErr = getSectionExtent(G, "__objc_selrefs"))
341       ObjCSelRefs = std::move(*ObjCSelRefsOrErr);
342     else
343       return ObjCSelRefsOrErr.takeError();
344 
345     // Record __objc_classlist.
346     if (auto ObjCClassListOrErr = getSectionExtent(G, "__objc_classlist"))
347       ObjCClassList = std::move(*ObjCClassListOrErr);
348     else
349       return ObjCClassListOrErr.takeError();
350 
351     // Dump the scraped inits.
352     LLVM_DEBUG({
353       dbgs() << "MachOPlatform: Scraped " << G.getName() << " init sections:\n";
354       dbgs() << "  __objc_selrefs: ";
355       if (ObjCSelRefs.NumPtrs)
356         dbgs() << ObjCSelRefs.NumPtrs << " pointer(s) at "
357                << formatv("{0:x16}", ObjCSelRefs.Address) << "\n";
358       else
359         dbgs() << "none\n";
360 
361       dbgs() << "  __objc_classlist: ";
362       if (ObjCClassList.NumPtrs)
363         dbgs() << ObjCClassList.NumPtrs << " pointer(s) at "
364                << formatv("{0:x16}", ObjCClassList.Address) << "\n";
365       else
366         dbgs() << "none\n";
367 
368       dbgs() << "  __mod_init_func: ";
369       if (ModInits.NumPtrs)
370         dbgs() << ModInits.NumPtrs << " pointer(s) at "
371                << formatv("{0:x16}", ModInits.Address) << "\n";
372       else
373         dbgs() << "none\n";
374     });
375 
376     MP.registerInitInfo(JD, ObjCImageInfoAddr, std::move(ModInits),
377                         std::move(ObjCSelRefs), std::move(ObjCClassList));
378 
379     return Error::success();
380   });
381 }
382 
383 ObjectLinkingLayer::Plugin::LocalDependenciesMap
384 MachOPlatform::InitScraperPlugin::getSyntheticSymbolLocalDependencies(
385     MaterializationResponsibility &MR) {
386   std::lock_guard<std::mutex> Lock(InitScraperMutex);
387   auto I = InitSymbolDeps.find(&MR);
388   if (I != InitSymbolDeps.end()) {
389     LocalDependenciesMap Result;
390     Result[MR.getInitializerSymbol()] = std::move(I->second);
391     InitSymbolDeps.erase(&MR);
392     return Result;
393   }
394   return LocalDependenciesMap();
395 }
396 
397 void MachOPlatform::InitScraperPlugin::preserveInitSectionIfPresent(
398     JITLinkSymbolVector &Symbols, jitlink::LinkGraph &G,
399     StringRef SectionName) {
400   if (auto *Sec = G.findSectionByName(SectionName)) {
401     auto SecBlocks = Sec->blocks();
402     if (!llvm::empty(SecBlocks))
403       Symbols.push_back(
404           &G.addAnonymousSymbol(**SecBlocks.begin(), 0, 0, false, true));
405   }
406 }
407 
408 Error MachOPlatform::InitScraperPlugin::processObjCImageInfo(
409     jitlink::LinkGraph &G, MaterializationResponsibility &MR) {
410 
411   // If there's an ObjC imagine info then either
412   //   (1) It's the first __objc_imageinfo we've seen in this JITDylib. In
413   //       this case we name and record it.
414   // OR
415   //   (2) We already have a recorded __objc_imageinfo for this JITDylib,
416   //       in which case we just verify it.
417   auto *ObjCImageInfo = G.findSectionByName("__objc_imageinfo");
418   if (!ObjCImageInfo)
419     return Error::success();
420 
421   auto ObjCImageInfoBlocks = ObjCImageInfo->blocks();
422 
423   // Check that the section is not empty if present.
424   if (llvm::empty(ObjCImageInfoBlocks))
425     return make_error<StringError>("Empty __objc_imageinfo section in " +
426                                        G.getName(),
427                                    inconvertibleErrorCode());
428 
429   // Check that there's only one block in the section.
430   if (std::next(ObjCImageInfoBlocks.begin()) != ObjCImageInfoBlocks.end())
431     return make_error<StringError>("Multiple blocks in __objc_imageinfo "
432                                    "section in " +
433                                        G.getName(),
434                                    inconvertibleErrorCode());
435 
436   // Check that the __objc_imageinfo section is unreferenced.
437   // FIXME: We could optimize this check if Symbols had a ref-count.
438   for (auto &Sec : G.sections()) {
439     if (&Sec != ObjCImageInfo)
440       for (auto *B : Sec.blocks())
441         for (auto &E : B->edges())
442           if (E.getTarget().isDefined() &&
443               &E.getTarget().getBlock().getSection() == ObjCImageInfo)
444             return make_error<StringError>("__objc_imageinfo is referenced "
445                                            "within file " +
446                                                G.getName(),
447                                            inconvertibleErrorCode());
448   }
449 
450   auto &ObjCImageInfoBlock = **ObjCImageInfoBlocks.begin();
451   auto *ObjCImageInfoData = ObjCImageInfoBlock.getContent().data();
452   auto Version = support::endian::read32(ObjCImageInfoData, G.getEndianness());
453   auto Flags =
454       support::endian::read32(ObjCImageInfoData + 4, G.getEndianness());
455 
456   // Lock the mutex while we verify / update the ObjCImageInfos map.
457   std::lock_guard<std::mutex> Lock(InitScraperMutex);
458 
459   auto ObjCImageInfoItr = ObjCImageInfos.find(&MR.getTargetJITDylib());
460   if (ObjCImageInfoItr != ObjCImageInfos.end()) {
461     // We've already registered an __objc_imageinfo section. Verify the
462     // content of this new section matches, then delete it.
463     if (ObjCImageInfoItr->second.first != Version)
464       return make_error<StringError>(
465           "ObjC version in " + G.getName() +
466               " does not match first registered version",
467           inconvertibleErrorCode());
468     if (ObjCImageInfoItr->second.second != Flags)
469       return make_error<StringError>("ObjC flags in " + G.getName() +
470                                          " do not match first registered flags",
471                                      inconvertibleErrorCode());
472 
473     // __objc_imageinfo is valid. Delete the block.
474     for (auto *S : ObjCImageInfo->symbols())
475       G.removeDefinedSymbol(*S);
476     G.removeBlock(ObjCImageInfoBlock);
477   } else {
478     // We haven't registered an __objc_imageinfo section yet. Register and
479     // move on. The section should already be marked no-dead-strip.
480     ObjCImageInfos[&MR.getTargetJITDylib()] = std::make_pair(Version, Flags);
481   }
482 
483   return Error::success();
484 }
485 
486 } // End namespace orc.
487 } // End namespace llvm.
488