1 //===-- X86WinEHState - Insert EH state updates for win32 exceptions ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // All functions using an MSVC EH personality use an explicitly updated state
11 // number stored in an exception registration stack object. The registration
12 // object is linked into a thread-local chain of registrations stored at fs:00.
13 // This pass adds the registration object and EH state updates.
15 //===----------------------------------------------------------------------===//
18 #include "llvm/Analysis/LibCallSemantics.h"
19 #include "llvm/CodeGen/MachineModuleInfo.h"
20 #include "llvm/CodeGen/Passes.h"
21 #include "llvm/CodeGen/WinEHFuncInfo.h"
22 #include "llvm/IR/Dominators.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/IRBuilder.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/PatternMatch.h"
29 #include "llvm/Pass.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
33 #include "llvm/Transforms/Utils/Cloning.h"
34 #include "llvm/Transforms/Utils/Local.h"
37 using namespace llvm::PatternMatch;
39 #define DEBUG_TYPE "winehstate"
42 class WinEHStatePass : public FunctionPass {
44 static char ID; // Pass identification, replacement for typeid.
46 WinEHStatePass() : FunctionPass(ID) {}
48 bool runOnFunction(Function &Fn) override;
50 bool doInitialization(Module &M) override;
52 bool doFinalization(Module &M) override;
54 void getAnalysisUsage(AnalysisUsage &AU) const override;
56 const char *getPassName() const override {
57 return "Windows 32-bit x86 EH state insertion";
61 void emitExceptionRegistrationRecord(Function *F);
63 void linkExceptionRegistration(IRBuilder<> &Builder, Function *Handler);
64 void unlinkExceptionRegistration(IRBuilder<> &Builder);
65 void addCXXStateStores(Function &F, MachineModuleInfo &MMI);
66 void addSEHStateStores(Function &F, MachineModuleInfo &MMI);
67 void addCXXStateStoresToFunclet(Value *ParentRegNode, WinEHFuncInfo &FuncInfo,
68 Function &F, int BaseState);
69 void insertStateNumberStore(Value *ParentRegNode, Instruction *IP, int State);
70 iplist<Instruction>::iterator
71 rewriteExceptionInfoIntrinsics(IntrinsicInst *Intrin);
73 Value *emitEHLSDA(IRBuilder<> &Builder, Function *F);
75 Function *generateLSDAInEAXThunk(Function *ParentFunc);
77 int escapeRegNode(Function &F);
79 // Module-level type getters.
80 Type *getEHLinkRegistrationType();
81 Type *getSEHRegistrationType();
82 Type *getCXXEHRegistrationType();
85 Module *TheModule = nullptr;
86 StructType *EHLinkRegistrationTy = nullptr;
87 StructType *CXXEHRegistrationTy = nullptr;
88 StructType *SEHRegistrationTy = nullptr;
89 Function *FrameRecover = nullptr;
90 Function *FrameAddress = nullptr;
91 Function *FrameEscape = nullptr;
94 EHPersonality Personality = EHPersonality::Unknown;
95 Function *PersonalityFn = nullptr;
97 /// The stack allocation containing all EH data, including the link in the
98 /// fs:00 chain and the current state.
99 AllocaInst *RegNode = nullptr;
101 /// Struct type of RegNode. Used for GEPing.
102 Type *RegNodeTy = nullptr;
104 /// The index of the state field of RegNode.
105 int StateFieldIndex = ~0U;
107 /// The linked list node subobject inside of RegNode.
108 Value *Link = nullptr;
112 FunctionPass *llvm::createX86WinEHStatePass() { return new WinEHStatePass(); }
114 char WinEHStatePass::ID = 0;
116 bool WinEHStatePass::doInitialization(Module &M) {
118 FrameEscape = Intrinsic::getDeclaration(TheModule, Intrinsic::frameescape);
119 FrameRecover = Intrinsic::getDeclaration(TheModule, Intrinsic::framerecover);
120 FrameAddress = Intrinsic::getDeclaration(TheModule, Intrinsic::frameaddress);
124 bool WinEHStatePass::doFinalization(Module &M) {
125 assert(TheModule == &M);
127 EHLinkRegistrationTy = nullptr;
128 CXXEHRegistrationTy = nullptr;
129 SEHRegistrationTy = nullptr;
130 FrameEscape = nullptr;
131 FrameRecover = nullptr;
132 FrameAddress = nullptr;
136 void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
137 // This pass should only insert a stack allocation, memory accesses, and
139 AU.setPreservesCFG();
142 bool WinEHStatePass::runOnFunction(Function &F) {
143 // If this is an outlined handler, don't do anything. We'll do state insertion
144 // for it in the parent.
145 StringRef WinEHParentName =
146 F.getFnAttribute("wineh-parent").getValueAsString();
147 if (WinEHParentName != F.getName() && !WinEHParentName.empty())
150 // Check the personality. Do nothing if this is not an MSVC personality.
151 LandingPadInst *LP = nullptr;
152 for (BasicBlock &BB : F) {
153 LP = BB.getLandingPadInst();
160 dyn_cast<Function>(LP->getPersonalityFn()->stripPointerCasts());
163 Personality = classifyEHPersonality(PersonalityFn);
164 if (!isMSVCEHPersonality(Personality))
167 // Disable frame pointer elimination in this function.
168 // FIXME: Do the nested handlers need to keep the parent ebp in ebp, or can we
169 // use an arbitrary register?
170 F.addFnAttr("no-frame-pointer-elim", "true");
172 emitExceptionRegistrationRecord(&F);
174 auto *MMIPtr = getAnalysisIfAvailable<MachineModuleInfo>();
175 assert(MMIPtr && "MachineModuleInfo should always be available");
176 MachineModuleInfo &MMI = *MMIPtr;
177 switch (Personality) {
178 default: llvm_unreachable("unexpected personality function");
179 case EHPersonality::MSVC_CXX: addCXXStateStores(F, MMI); break;
180 case EHPersonality::MSVC_X86SEH: addSEHStateStores(F, MMI); break;
183 // Reset per-function state.
184 PersonalityFn = nullptr;
185 Personality = EHPersonality::Unknown;
189 /// Get the common EH registration subobject:
190 /// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
191 /// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
192 /// struct EHRegistrationNode {
193 /// EHRegistrationNode *Next;
194 /// PEXCEPTION_ROUTINE Handler;
196 Type *WinEHStatePass::getEHLinkRegistrationType() {
197 if (EHLinkRegistrationTy)
198 return EHLinkRegistrationTy;
199 LLVMContext &Context = TheModule->getContext();
200 EHLinkRegistrationTy = StructType::create(Context, "EHRegistrationNode");
202 EHLinkRegistrationTy->getPointerTo(0), // EHRegistrationNode *Next
203 Type::getInt8PtrTy(Context) // EXCEPTION_DISPOSITION (*Handler)(...)
205 EHLinkRegistrationTy->setBody(FieldTys, false);
206 return EHLinkRegistrationTy;
209 /// The __CxxFrameHandler3 registration node:
210 /// struct CXXExceptionRegistration {
212 /// EHRegistrationNode SubRecord;
213 /// int32_t TryLevel;
215 Type *WinEHStatePass::getCXXEHRegistrationType() {
216 if (CXXEHRegistrationTy)
217 return CXXEHRegistrationTy;
218 LLVMContext &Context = TheModule->getContext();
220 Type::getInt8PtrTy(Context), // void *SavedESP
221 getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
222 Type::getInt32Ty(Context) // int32_t TryLevel
224 CXXEHRegistrationTy =
225 StructType::create(FieldTys, "CXXExceptionRegistration");
226 return CXXEHRegistrationTy;
229 /// The _except_handler3/4 registration node:
230 /// struct EH4ExceptionRegistration {
232 /// _EXCEPTION_POINTERS *ExceptionPointers;
233 /// EHRegistrationNode SubRecord;
234 /// int32_t EncodedScopeTable;
235 /// int32_t TryLevel;
237 Type *WinEHStatePass::getSEHRegistrationType() {
238 if (SEHRegistrationTy)
239 return SEHRegistrationTy;
240 LLVMContext &Context = TheModule->getContext();
242 Type::getInt8PtrTy(Context), // void *SavedESP
243 Type::getInt8PtrTy(Context), // void *ExceptionPointers
244 getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
245 Type::getInt32Ty(Context), // int32_t EncodedScopeTable
246 Type::getInt32Ty(Context) // int32_t TryLevel
248 SEHRegistrationTy = StructType::create(FieldTys, "SEHExceptionRegistration");
249 return SEHRegistrationTy;
252 // Emit an exception registration record. These are stack allocations with the
253 // common subobject of two pointers: the previous registration record (the old
254 // fs:00) and the personality function for the current frame. The data before
255 // and after that is personality function specific.
256 void WinEHStatePass::emitExceptionRegistrationRecord(Function *F) {
257 assert(Personality == EHPersonality::MSVC_CXX ||
258 Personality == EHPersonality::MSVC_X86SEH);
260 StringRef PersonalityName = PersonalityFn->getName();
261 IRBuilder<> Builder(&F->getEntryBlock(), F->getEntryBlock().begin());
262 Type *Int8PtrType = Builder.getInt8PtrTy();
263 if (Personality == EHPersonality::MSVC_CXX) {
264 RegNodeTy = getCXXEHRegistrationType();
265 RegNode = Builder.CreateAlloca(RegNodeTy);
266 // FIXME: We can skip this in -GS- mode, when we figure that out.
267 // SavedESP = llvm.stacksave()
268 Value *SP = Builder.CreateCall(
269 Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
270 Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
273 insertStateNumberStore(RegNode, Builder.GetInsertPoint(), -1);
274 // Handler = __ehhandler$F
275 Function *Trampoline = generateLSDAInEAXThunk(F);
276 Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 1);
277 linkExceptionRegistration(Builder, Trampoline);
278 } else if (Personality == EHPersonality::MSVC_X86SEH) {
279 // If _except_handler4 is in use, some additional guard checks and prologue
280 // stuff is required.
281 bool UseStackGuard = (PersonalityName == "_except_handler4");
282 RegNodeTy = getSEHRegistrationType();
283 RegNode = Builder.CreateAlloca(RegNodeTy);
284 // SavedESP = llvm.stacksave()
285 Value *SP = Builder.CreateCall(
286 Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
287 Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
288 // TryLevel = -2 / -1
290 insertStateNumberStore(RegNode, Builder.GetInsertPoint(),
291 UseStackGuard ? -2 : -1);
292 // ScopeTable = llvm.x86.seh.lsda(F)
293 Value *FI8 = Builder.CreateBitCast(F, Int8PtrType);
294 Value *LSDA = Builder.CreateCall(
295 Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
296 Type *Int32Ty = Type::getInt32Ty(TheModule->getContext());
297 LSDA = Builder.CreatePtrToInt(LSDA, Int32Ty);
298 // If using _except_handler4, xor the address of the table with
299 // __security_cookie.
302 TheModule->getOrInsertGlobal("__security_cookie", Int32Ty);
303 Value *Val = Builder.CreateLoad(Int32Ty, Cookie);
304 LSDA = Builder.CreateXor(LSDA, Val);
306 Builder.CreateStore(LSDA, Builder.CreateStructGEP(RegNodeTy, RegNode, 3));
307 Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 2);
308 linkExceptionRegistration(Builder, PersonalityFn);
310 llvm_unreachable("unexpected personality function");
313 // Insert an unlink before all returns.
314 for (BasicBlock &BB : *F) {
315 TerminatorInst *T = BB.getTerminator();
316 if (!isa<ReturnInst>(T))
318 Builder.SetInsertPoint(T);
319 unlinkExceptionRegistration(Builder);
323 Value *WinEHStatePass::emitEHLSDA(IRBuilder<> &Builder, Function *F) {
324 Value *FI8 = Builder.CreateBitCast(F, Type::getInt8PtrTy(F->getContext()));
325 return Builder.CreateCall(
326 Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
329 /// Generate a thunk that puts the LSDA of ParentFunc in EAX and then calls
330 /// PersonalityFn, forwarding the parameters passed to PEXCEPTION_ROUTINE:
331 /// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
332 /// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
333 /// We essentially want this code:
335 /// jmpl ___CxxFrameHandler3
336 Function *WinEHStatePass::generateLSDAInEAXThunk(Function *ParentFunc) {
337 LLVMContext &Context = ParentFunc->getContext();
338 Type *Int32Ty = Type::getInt32Ty(Context);
339 Type *Int8PtrType = Type::getInt8PtrTy(Context);
340 Type *ArgTys[5] = {Int8PtrType, Int8PtrType, Int8PtrType, Int8PtrType,
342 FunctionType *TrampolineTy =
343 FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 4),
345 FunctionType *TargetFuncTy =
346 FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 5),
348 Function *Trampoline = Function::Create(
349 TrampolineTy, GlobalValue::InternalLinkage,
350 Twine("__ehhandler$") + ParentFunc->getName(), TheModule);
351 BasicBlock *EntryBB = BasicBlock::Create(Context, "entry", Trampoline);
352 IRBuilder<> Builder(EntryBB);
353 Value *LSDA = emitEHLSDA(Builder, ParentFunc);
354 Value *CastPersonality =
355 Builder.CreateBitCast(PersonalityFn, TargetFuncTy->getPointerTo());
356 auto AI = Trampoline->arg_begin();
357 Value *Args[5] = {LSDA, AI++, AI++, AI++, AI++};
358 CallInst *Call = Builder.CreateCall(CastPersonality, Args);
359 // Can't use musttail due to prototype mismatch, but we can use tail.
360 Call->setTailCall(true);
361 // Set inreg so we pass it in EAX.
362 Call->addAttribute(1, Attribute::InReg);
363 Builder.CreateRet(Call);
367 void WinEHStatePass::linkExceptionRegistration(IRBuilder<> &Builder,
369 // Emit the .safeseh directive for this function.
370 Handler->addFnAttr("safeseh");
372 Type *LinkTy = getEHLinkRegistrationType();
374 Value *HandlerI8 = Builder.CreateBitCast(Handler, Builder.getInt8PtrTy());
375 Builder.CreateStore(HandlerI8, Builder.CreateStructGEP(LinkTy, Link, 1));
378 Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
379 Value *Next = Builder.CreateLoad(FSZero);
380 Builder.CreateStore(Next, Builder.CreateStructGEP(LinkTy, Link, 0));
382 Builder.CreateStore(Link, FSZero);
385 void WinEHStatePass::unlinkExceptionRegistration(IRBuilder<> &Builder) {
386 // Clone Link into the current BB for better address mode folding.
387 if (auto *GEP = dyn_cast<GetElementPtrInst>(Link)) {
388 GEP = cast<GetElementPtrInst>(GEP->clone());
392 Type *LinkTy = getEHLinkRegistrationType();
393 // [fs:00] = Link->Next
395 Builder.CreateLoad(Builder.CreateStructGEP(LinkTy, Link, 0));
397 Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
398 Builder.CreateStore(Next, FSZero);
401 void WinEHStatePass::addCXXStateStores(Function &F, MachineModuleInfo &MMI) {
402 WinEHFuncInfo &FuncInfo = MMI.getWinEHFuncInfo(&F);
403 calculateWinCXXEHStateNumbers(&F, FuncInfo);
405 // The base state for the parent is -1.
406 addCXXStateStoresToFunclet(RegNode, FuncInfo, F, -1);
408 // Set up RegNodeEscapeIndex
409 int RegNodeEscapeIndex = escapeRegNode(F);
411 // Only insert stores in catch handlers.
413 ConstantExpr::getBitCast(&F, Type::getInt8PtrTy(TheModule->getContext()));
414 for (auto P : FuncInfo.HandlerBaseState) {
415 Function *Handler = const_cast<Function *>(P.first);
416 int BaseState = P.second;
417 IRBuilder<> Builder(&Handler->getEntryBlock(),
418 Handler->getEntryBlock().begin());
419 // FIXME: Find and reuse such a call if present.
420 Value *ParentFP = Builder.CreateCall(FrameAddress, {Builder.getInt32(1)});
421 Value *RecoveredRegNode = Builder.CreateCall(
422 FrameRecover, {FI8, ParentFP, Builder.getInt32(RegNodeEscapeIndex)});
424 Builder.CreateBitCast(RecoveredRegNode, RegNodeTy->getPointerTo(0));
425 addCXXStateStoresToFunclet(RecoveredRegNode, FuncInfo, *Handler, BaseState);
429 /// Escape RegNode so that we can access it from child handlers. Find the call
430 /// to frameescape, if any, in the entry block and append RegNode to the list
432 int WinEHStatePass::escapeRegNode(Function &F) {
433 // Find the call to frameescape and extract its arguments.
434 IntrinsicInst *EscapeCall = nullptr;
435 for (Instruction &I : F.getEntryBlock()) {
436 IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
437 if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
442 SmallVector<Value *, 8> Args;
444 auto Ops = EscapeCall->arg_operands();
445 Args.append(Ops.begin(), Ops.end());
447 Args.push_back(RegNode);
449 // Replace the call (if it exists) with new one. Otherwise, insert at the end
450 // of the entry block.
451 IRBuilder<> Builder(&F.getEntryBlock(),
452 EscapeCall ? EscapeCall : F.getEntryBlock().end());
453 Builder.CreateCall(FrameEscape, Args);
455 EscapeCall->eraseFromParent();
456 return Args.size() - 1;
459 void WinEHStatePass::addCXXStateStoresToFunclet(Value *ParentRegNode,
460 WinEHFuncInfo &FuncInfo,
461 Function &F, int BaseState) {
462 // Iterate all the instructions and emit state number stores.
463 for (BasicBlock &BB : F) {
464 for (Instruction &I : BB) {
465 if (auto *CI = dyn_cast<CallInst>(&I)) {
466 // Possibly throwing call instructions have no actions to take after
467 // an unwind. Ensure they are in the -1 state.
468 if (CI->doesNotThrow())
470 insertStateNumberStore(ParentRegNode, CI, BaseState);
471 } else if (auto *II = dyn_cast<InvokeInst>(&I)) {
472 // Look up the state number of the landingpad this unwinds to.
473 LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst();
474 // FIXME: Why does this assertion fail?
475 //assert(FuncInfo.LandingPadStateMap.count(LPI) && "LP has no state!");
476 int State = FuncInfo.LandingPadStateMap[LPI];
477 insertStateNumberStore(ParentRegNode, II, State);
483 /// Assign every distinct landingpad a unique state number for SEH. Unlike C++
484 /// EH, we can use this very simple algorithm while C++ EH cannot because catch
485 /// handlers aren't outlined and the runtime doesn't have to figure out which
486 /// catch handler frame to unwind to.
487 /// FIXME: __finally blocks are outlined, so this approach may break down there.
488 void WinEHStatePass::addSEHStateStores(Function &F, MachineModuleInfo &MMI) {
489 WinEHFuncInfo &FuncInfo = MMI.getWinEHFuncInfo(&F);
491 // Iterate all the instructions and emit state number stores.
493 for (BasicBlock &BB : F) {
494 for (auto I = BB.begin(), E = BB.end(); I != E; ++I) {
495 if (auto *CI = dyn_cast<CallInst>(I)) {
496 auto *Intrin = dyn_cast<IntrinsicInst>(CI);
498 I = rewriteExceptionInfoIntrinsics(Intrin);
499 // Calls that "don't throw" are considered to be able to throw asynch
500 // exceptions, but intrinsics cannot.
503 insertStateNumberStore(RegNode, CI, -1);
504 } else if (auto *II = dyn_cast<InvokeInst>(I)) {
505 // Look up the state number of the landingpad this unwinds to.
506 LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst();
508 FuncInfo.LandingPadStateMap.insert(std::make_pair(LPI, 0));
509 auto Iter = InsertionPair.first;
510 int &State = Iter->second;
511 bool Inserted = InsertionPair.second;
513 // Each action consumes a state number.
514 auto *EHActions = cast<IntrinsicInst>(LPI->getNextNode());
515 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
516 parseEHActions(EHActions, ActionList);
517 assert(!ActionList.empty());
518 CurState += ActionList.size();
519 State += ActionList.size() - 1;
521 insertStateNumberStore(RegNode, II, State);
527 /// Rewrite llvm.eh.exceptioncode and llvm.eh.exceptioninfo to memory loads in
529 iplist<Instruction>::iterator
530 WinEHStatePass::rewriteExceptionInfoIntrinsics(IntrinsicInst *Intrin) {
531 Intrinsic::ID ID = Intrin->getIntrinsicID();
532 if (ID != Intrinsic::eh_exceptioncode && ID != Intrinsic::eh_exceptioninfo)
535 // RegNode->ExceptionPointers
536 IRBuilder<> Builder(Intrin);
538 Builder.CreateLoad(Builder.CreateStructGEP(RegNodeTy, RegNode, 1));
540 if (ID == Intrinsic::eh_exceptioncode) {
541 // Ptrs->ExceptionRecord->Code
542 Ptrs = Builder.CreateBitCast(
543 Ptrs, Builder.getInt32Ty()->getPointerTo()->getPointerTo());
544 Value *Rec = Builder.CreateLoad(Ptrs);
545 Res = Builder.CreateLoad(Rec);
549 Intrin->replaceAllUsesWith(Res);
550 return Intrin->eraseFromParent();
553 void WinEHStatePass::insertStateNumberStore(Value *ParentRegNode,
554 Instruction *IP, int State) {
555 IRBuilder<> Builder(IP);
557 Builder.CreateStructGEP(RegNodeTy, ParentRegNode, StateFieldIndex);
558 Builder.CreateStore(Builder.getInt32(State), StateField);