llvm-project/llvm/lib/Target/X86/X86WinEHState.cpp

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//===-- X86WinEHState - Insert EH state updates for win32 exceptions ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// All functions using an MSVC EH personality use an explicitly updated state
// number stored in an exception registration stack object. The registration
// object is linked into a thread-local chain of registrations stored at fs:00.
// This pass adds the registration object and EH state updates.
//
//===----------------------------------------------------------------------===//
#include "X86.h"
#include "llvm/Analysis/LibCallSemantics.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/WinEHFuncInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "winehstate"
namespace {
class WinEHStatePass : public FunctionPass {
public:
static char ID; // Pass identification, replacement for typeid.
WinEHStatePass() : FunctionPass(ID) {}
bool runOnFunction(Function &Fn) override;
bool doInitialization(Module &M) override;
bool doFinalization(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
const char *getPassName() const override {
return "Windows 32-bit x86 EH state insertion";
}
private:
void emitExceptionRegistrationRecord(Function *F);
void linkExceptionRegistration(IRBuilder<> &Builder, Value *Handler);
void unlinkExceptionRegistration(IRBuilder<> &Builder);
void addCXXStateStores(Function &F, MachineModuleInfo &MMI);
void addCXXStateStoresToFunclet(Value *ParentRegNode, WinEHFuncInfo &FuncInfo,
Function &F, int BaseState);
void insertStateNumberStore(Value *ParentRegNode, Instruction *IP, int State);
Value *emitEHLSDA(IRBuilder<> &Builder, Function *F);
Function *generateLSDAInEAXThunk(Function *ParentFunc);
int escapeRegNode(Function &F);
// Module-level type getters.
Type *getEHLinkRegistrationType();
Type *getSEHRegistrationType();
Type *getCXXEHRegistrationType();
// Per-module data.
Module *TheModule = nullptr;
StructType *EHLinkRegistrationTy = nullptr;
StructType *CXXEHRegistrationTy = nullptr;
StructType *SEHRegistrationTy = nullptr;
// Per-function state
EHPersonality Personality = EHPersonality::Unknown;
Function *PersonalityFn = nullptr;
/// The stack allocation containing all EH data, including the link in the
/// fs:00 chain and the current state.
AllocaInst *RegNode = nullptr;
/// Struct type of RegNode. Used for GEPing.
Type *RegNodeTy = nullptr;
/// The index of the state field of RegNode.
int StateFieldIndex = ~0U;
/// The linked list node subobject inside of RegNode.
Value *Link = nullptr;
};
}
FunctionPass *llvm::createX86WinEHStatePass() { return new WinEHStatePass(); }
char WinEHStatePass::ID = 0;
bool WinEHStatePass::doInitialization(Module &M) {
TheModule = &M;
return false;
}
bool WinEHStatePass::doFinalization(Module &M) {
assert(TheModule == &M);
TheModule = nullptr;
EHLinkRegistrationTy = nullptr;
CXXEHRegistrationTy = nullptr;
SEHRegistrationTy = nullptr;
return false;
}
void WinEHStatePass::getAnalysisUsage(AnalysisUsage &AU) const {
// This pass should only insert a stack allocation, memory accesses, and
// framerecovers.
AU.setPreservesCFG();
}
bool WinEHStatePass::runOnFunction(Function &F) {
// If this is an outlined handler, don't do anything. We'll do state insertion
// for it in the parent.
StringRef WinEHParentName =
F.getFnAttribute("wineh-parent").getValueAsString();
if (WinEHParentName != F.getName() && !WinEHParentName.empty())
return false;
// Check the personality. Do nothing if this is not an MSVC personality.
LandingPadInst *LP = nullptr;
for (BasicBlock &BB : F) {
LP = BB.getLandingPadInst();
if (LP)
break;
}
if (!LP)
return false;
PersonalityFn =
dyn_cast<Function>(LP->getPersonalityFn()->stripPointerCasts());
if (!PersonalityFn)
return false;
Personality = classifyEHPersonality(PersonalityFn);
if (!isMSVCEHPersonality(Personality))
return false;
// Disable frame pointer elimination in this function.
// FIXME: Do the nested handlers need to keep the parent ebp in ebp, or can we
// use an arbitrary register?
F.addFnAttr("no-frame-pointer-elim", "true");
emitExceptionRegistrationRecord(&F);
auto *MMIPtr = getAnalysisIfAvailable<MachineModuleInfo>();
assert(MMIPtr && "MachineModuleInfo should always be available");
MachineModuleInfo &MMI = *MMIPtr;
if (Personality == EHPersonality::MSVC_CXX) {
addCXXStateStores(F, MMI);
}
// Reset per-function state.
PersonalityFn = nullptr;
Personality = EHPersonality::Unknown;
return true;
}
/// Get the common EH registration subobject:
/// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
/// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
/// struct EHRegistrationNode {
/// EHRegistrationNode *Next;
/// PEXCEPTION_ROUTINE Handler;
/// };
Type *WinEHStatePass::getEHLinkRegistrationType() {
if (EHLinkRegistrationTy)
return EHLinkRegistrationTy;
LLVMContext &Context = TheModule->getContext();
EHLinkRegistrationTy = StructType::create(Context, "EHRegistrationNode");
Type *FieldTys[] = {
EHLinkRegistrationTy->getPointerTo(0), // EHRegistrationNode *Next
Type::getInt8PtrTy(Context) // EXCEPTION_DISPOSITION (*Handler)(...)
};
EHLinkRegistrationTy->setBody(FieldTys, false);
return EHLinkRegistrationTy;
}
/// The __CxxFrameHandler3 registration node:
/// struct CXXExceptionRegistration {
/// void *SavedESP;
/// EHRegistrationNode SubRecord;
/// int32_t TryLevel;
/// };
Type *WinEHStatePass::getCXXEHRegistrationType() {
if (CXXEHRegistrationTy)
return CXXEHRegistrationTy;
LLVMContext &Context = TheModule->getContext();
Type *FieldTys[] = {
Type::getInt8PtrTy(Context), // void *SavedESP
getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
Type::getInt32Ty(Context) // int32_t TryLevel
};
CXXEHRegistrationTy =
StructType::create(FieldTys, "CXXExceptionRegistration");
return CXXEHRegistrationTy;
}
/// The _except_handler3/4 registration node:
/// struct EH4ExceptionRegistration {
/// void *SavedESP;
/// _EXCEPTION_POINTERS *ExceptionPointers;
/// EHRegistrationNode SubRecord;
/// int32_t EncodedScopeTable;
/// int32_t TryLevel;
/// };
Type *WinEHStatePass::getSEHRegistrationType() {
if (SEHRegistrationTy)
return SEHRegistrationTy;
LLVMContext &Context = TheModule->getContext();
Type *FieldTys[] = {
Type::getInt8PtrTy(Context), // void *SavedESP
Type::getInt8PtrTy(Context), // void *ExceptionPointers
getEHLinkRegistrationType(), // EHRegistrationNode SubRecord
Type::getInt32Ty(Context), // int32_t EncodedScopeTable
Type::getInt32Ty(Context) // int32_t TryLevel
};
SEHRegistrationTy = StructType::create(FieldTys, "SEHExceptionRegistration");
return SEHRegistrationTy;
}
// Emit an exception registration record. These are stack allocations with the
// common subobject of two pointers: the previous registration record (the old
// fs:00) and the personality function for the current frame. The data before
// and after that is personality function specific.
void WinEHStatePass::emitExceptionRegistrationRecord(Function *F) {
assert(Personality == EHPersonality::MSVC_CXX ||
Personality == EHPersonality::MSVC_X86SEH);
StringRef PersonalityName = PersonalityFn->getName();
IRBuilder<> Builder(&F->getEntryBlock(), F->getEntryBlock().begin());
Type *Int8PtrType = Builder.getInt8PtrTy();
if (Personality == EHPersonality::MSVC_CXX) {
RegNodeTy = getCXXEHRegistrationType();
RegNode = Builder.CreateAlloca(RegNodeTy);
// FIXME: We can skip this in -GS- mode, when we figure that out.
// SavedESP = llvm.stacksave()
Value *SP = Builder.CreateCall(
Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
// TryLevel = -1
StateFieldIndex = 2;
insertStateNumberStore(RegNode, Builder.GetInsertPoint(), -1);
// Handler = __ehhandler$F
Function *Trampoline = generateLSDAInEAXThunk(F);
Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 1);
linkExceptionRegistration(Builder, Trampoline);
} else if (Personality == EHPersonality::MSVC_X86SEH) {
// If _except_handler4 is in use, some additional guard checks and prologue
// stuff is required.
bool UseStackGuard = (PersonalityName == "_except_handler4");
RegNodeTy = getSEHRegistrationType();
RegNode = Builder.CreateAlloca(RegNodeTy);
// SavedESP = llvm.stacksave()
Value *SP = Builder.CreateCall(
Intrinsic::getDeclaration(TheModule, Intrinsic::stacksave), {});
Builder.CreateStore(SP, Builder.CreateStructGEP(RegNodeTy, RegNode, 0));
// TryLevel = -2 / -1
StateFieldIndex = 4;
insertStateNumberStore(RegNode, Builder.GetInsertPoint(),
UseStackGuard ? -2 : -1);
// ScopeTable = llvm.x86.seh.lsda(F)
Value *FI8 = Builder.CreateBitCast(F, Int8PtrType);
Value *LSDA = Builder.CreateCall(
Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
Type *Int32Ty = Type::getInt32Ty(TheModule->getContext());
LSDA = Builder.CreatePtrToInt(LSDA, Int32Ty);
// If using _except_handler4, xor the address of the table with
// __security_cookie.
if (UseStackGuard) {
Value *Cookie =
TheModule->getOrInsertGlobal("__security_cookie", Int32Ty);
Value *Val = Builder.CreateLoad(Int32Ty, Cookie);
LSDA = Builder.CreateXor(LSDA, Val);
}
Builder.CreateStore(LSDA, Builder.CreateStructGEP(RegNodeTy, RegNode, 3));
Link = Builder.CreateStructGEP(RegNodeTy, RegNode, 2);
linkExceptionRegistration(Builder, PersonalityFn);
} else {
llvm_unreachable("unexpected personality function");
}
// Insert an unlink before all returns.
for (BasicBlock &BB : *F) {
TerminatorInst *T = BB.getTerminator();
if (!isa<ReturnInst>(T))
continue;
Builder.SetInsertPoint(T);
unlinkExceptionRegistration(Builder);
}
}
Value *WinEHStatePass::emitEHLSDA(IRBuilder<> &Builder, Function *F) {
Value *FI8 = Builder.CreateBitCast(F, Type::getInt8PtrTy(F->getContext()));
return Builder.CreateCall(
Intrinsic::getDeclaration(TheModule, Intrinsic::x86_seh_lsda), FI8);
}
/// Generate a thunk that puts the LSDA of ParentFunc in EAX and then calls
/// PersonalityFn, forwarding the parameters passed to PEXCEPTION_ROUTINE:
/// typedef _EXCEPTION_DISPOSITION (*PEXCEPTION_ROUTINE)(
/// _EXCEPTION_RECORD *, void *, _CONTEXT *, void *);
/// We essentially want this code:
/// movl $lsda, %eax
/// jmpl ___CxxFrameHandler3
Function *WinEHStatePass::generateLSDAInEAXThunk(Function *ParentFunc) {
LLVMContext &Context = ParentFunc->getContext();
Type *Int32Ty = Type::getInt32Ty(Context);
Type *Int8PtrType = Type::getInt8PtrTy(Context);
Type *ArgTys[5] = {Int8PtrType, Int8PtrType, Int8PtrType, Int8PtrType,
Int8PtrType};
FunctionType *TrampolineTy =
FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 4),
/*isVarArg=*/false);
FunctionType *TargetFuncTy =
FunctionType::get(Int32Ty, makeArrayRef(&ArgTys[0], 5),
/*isVarArg=*/false);
Function *Trampoline = Function::Create(
TrampolineTy, GlobalValue::InternalLinkage,
Twine("__ehhandler$") + ParentFunc->getName(), TheModule);
BasicBlock *EntryBB = BasicBlock::Create(Context, "entry", Trampoline);
IRBuilder<> Builder(EntryBB);
Value *LSDA = emitEHLSDA(Builder, ParentFunc);
Value *CastPersonality =
Builder.CreateBitCast(PersonalityFn, TargetFuncTy->getPointerTo());
auto AI = Trampoline->arg_begin();
Value *Args[5] = {LSDA, AI++, AI++, AI++, AI++};
CallInst *Call = Builder.CreateCall(CastPersonality, Args);
// Can't use musttail due to prototype mismatch, but we can use tail.
Call->setTailCall(true);
// Set inreg so we pass it in EAX.
Call->addAttribute(1, Attribute::InReg);
Builder.CreateRet(Call);
return Trampoline;
}
void WinEHStatePass::linkExceptionRegistration(IRBuilder<> &Builder,
Value *Handler) {
Type *LinkTy = getEHLinkRegistrationType();
// Handler = Handler
Handler = Builder.CreateBitCast(Handler, Builder.getInt8PtrTy());
Builder.CreateStore(Handler, Builder.CreateStructGEP(LinkTy, Link, 1));
// Next = [fs:00]
Constant *FSZero =
Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
Value *Next = Builder.CreateLoad(FSZero);
Builder.CreateStore(Next, Builder.CreateStructGEP(LinkTy, Link, 0));
// [fs:00] = Link
Builder.CreateStore(Link, FSZero);
}
void WinEHStatePass::unlinkExceptionRegistration(IRBuilder<> &Builder) {
// Clone Link into the current BB for better address mode folding.
if (auto *GEP = dyn_cast<GetElementPtrInst>(Link)) {
GEP = cast<GetElementPtrInst>(GEP->clone());
Builder.Insert(GEP);
Link = GEP;
}
Type *LinkTy = getEHLinkRegistrationType();
// [fs:00] = Link->Next
Value *Next =
Builder.CreateLoad(Builder.CreateStructGEP(LinkTy, Link, 0));
Constant *FSZero =
Constant::getNullValue(LinkTy->getPointerTo()->getPointerTo(257));
Builder.CreateStore(Next, FSZero);
}
void WinEHStatePass::addCXXStateStores(Function &F, MachineModuleInfo &MMI) {
WinEHFuncInfo &FuncInfo = MMI.getWinEHFuncInfo(&F);
calculateWinCXXEHStateNumbers(&F, FuncInfo);
// The base state for the parent is -1.
addCXXStateStoresToFunclet(RegNode, FuncInfo, F, -1);
// Set up RegNodeEscapeIndex
int RegNodeEscapeIndex = escapeRegNode(F);
// Only insert stores in catch handlers.
Function *FrameRecover =
Intrinsic::getDeclaration(TheModule, Intrinsic::framerecover);
Function *FrameAddress =
Intrinsic::getDeclaration(TheModule, Intrinsic::frameaddress);
Constant *FI8 =
ConstantExpr::getBitCast(&F, Type::getInt8PtrTy(TheModule->getContext()));
for (auto P : FuncInfo.HandlerBaseState) {
Function *Handler = const_cast<Function *>(P.first);
int BaseState = P.second;
IRBuilder<> Builder(&Handler->getEntryBlock(),
Handler->getEntryBlock().begin());
// FIXME: Find and reuse such a call if present.
Value *ParentFP = Builder.CreateCall(FrameAddress, {Builder.getInt32(1)});
Value *RecoveredRegNode = Builder.CreateCall(
FrameRecover, {FI8, ParentFP, Builder.getInt32(RegNodeEscapeIndex)});
RecoveredRegNode =
Builder.CreateBitCast(RecoveredRegNode, RegNodeTy->getPointerTo(0));
addCXXStateStoresToFunclet(RecoveredRegNode, FuncInfo, *Handler, BaseState);
}
}
/// Escape RegNode so that we can access it from child handlers. Find the call
/// to frameescape, if any, in the entry block and append RegNode to the list
/// of arguments.
int WinEHStatePass::escapeRegNode(Function &F) {
// Find the call to frameescape and extract its arguments.
IntrinsicInst *EscapeCall = nullptr;
for (Instruction &I : F.getEntryBlock()) {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
EscapeCall = II;
break;
}
}
SmallVector<Value *, 8> Args;
if (EscapeCall) {
auto Ops = EscapeCall->arg_operands();
Args.append(Ops.begin(), Ops.end());
}
Args.push_back(RegNode);
// Replace the call (if it exists) with new one. Otherwise, insert at the end
// of the entry block.
IRBuilder<> Builder(&F.getEntryBlock(),
EscapeCall ? EscapeCall : F.getEntryBlock().end());
Builder.CreateCall(
Intrinsic::getDeclaration(TheModule, Intrinsic::frameescape), Args);
if (EscapeCall)
EscapeCall->eraseFromParent();
return Args.size() - 1;
}
void WinEHStatePass::addCXXStateStoresToFunclet(Value *ParentRegNode,
WinEHFuncInfo &FuncInfo,
Function &F, int BaseState) {
// Iterate all the instructions and emit state number stores.
for (BasicBlock &BB : F) {
for (Instruction &I : BB) {
if (auto *CI = dyn_cast<CallInst>(&I)) {
// Possibly throwing call instructions have no actions to take after
// an unwind. Ensure they are in the -1 state.
if (CI->doesNotThrow())
continue;
insertStateNumberStore(ParentRegNode, CI, BaseState);
} else if (auto *II = dyn_cast<InvokeInst>(&I)) {
// Look up the state number of the landingpad this unwinds to.
LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst();
// FIXME: Why does this assertion fail?
//assert(FuncInfo.LandingPadStateMap.count(LPI) && "LP has no state!");
int State = FuncInfo.LandingPadStateMap[LPI];
insertStateNumberStore(ParentRegNode, II, State);
}
}
}
}
void WinEHStatePass::insertStateNumberStore(Value *ParentRegNode,
Instruction *IP, int State) {
IRBuilder<> Builder(IP);
Value *StateField =
Builder.CreateStructGEP(RegNodeTy, ParentRegNode, StateFieldIndex);
Builder.CreateStore(Builder.getInt32(State), StateField);
}