forked from OSchip/llvm-project
168 lines
5.6 KiB
C++
168 lines
5.6 KiB
C++
//===-- CrossDSOCFI.cpp - Externalize this module's CFI checks ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass exports all llvm.bitset's found in the module in the form of a
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// __cfi_check function, which can be used to verify cross-DSO call targets.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO/CrossDSOCFI.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/EquivalenceClasses.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/Constant.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalObject.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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using namespace llvm;
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#define DEBUG_TYPE "cross-dso-cfi"
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STATISTIC(NumTypeIds, "Number of unique type identifiers");
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namespace {
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struct CrossDSOCFI : public ModulePass {
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static char ID;
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CrossDSOCFI() : ModulePass(ID) {
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initializeCrossDSOCFIPass(*PassRegistry::getPassRegistry());
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}
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MDNode *VeryLikelyWeights;
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ConstantInt *extractNumericTypeId(MDNode *MD);
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void buildCFICheck(Module &M);
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bool runOnModule(Module &M) override;
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};
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} // anonymous namespace
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INITIALIZE_PASS_BEGIN(CrossDSOCFI, "cross-dso-cfi", "Cross-DSO CFI", false,
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false)
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INITIALIZE_PASS_END(CrossDSOCFI, "cross-dso-cfi", "Cross-DSO CFI", false, false)
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char CrossDSOCFI::ID = 0;
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ModulePass *llvm::createCrossDSOCFIPass() { return new CrossDSOCFI; }
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/// Extracts a numeric type identifier from an MDNode containing type metadata.
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ConstantInt *CrossDSOCFI::extractNumericTypeId(MDNode *MD) {
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// This check excludes vtables for classes inside anonymous namespaces.
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auto TM = dyn_cast<ValueAsMetadata>(MD->getOperand(1));
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if (!TM)
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return nullptr;
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auto C = dyn_cast_or_null<ConstantInt>(TM->getValue());
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if (!C) return nullptr;
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// We are looking for i64 constants.
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if (C->getBitWidth() != 64) return nullptr;
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return C;
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}
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/// buildCFICheck - emits __cfi_check for the current module.
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void CrossDSOCFI::buildCFICheck(Module &M) {
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// FIXME: verify that __cfi_check ends up near the end of the code section,
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// but before the jump slots created in LowerTypeTests.
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llvm::DenseSet<uint64_t> TypeIds;
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SmallVector<MDNode *, 2> Types;
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for (GlobalObject &GO : M.global_objects()) {
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Types.clear();
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GO.getMetadata(LLVMContext::MD_type, Types);
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for (MDNode *Type : Types) {
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// Sanity check. GO must not be a function declaration.
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assert(!isa<Function>(&GO) || !cast<Function>(&GO)->isDeclaration());
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if (ConstantInt *TypeId = extractNumericTypeId(Type))
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TypeIds.insert(TypeId->getZExtValue());
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}
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}
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LLVMContext &Ctx = M.getContext();
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Constant *C = M.getOrInsertFunction(
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"__cfi_check", Type::getVoidTy(Ctx), Type::getInt64Ty(Ctx),
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Type::getInt8PtrTy(Ctx), Type::getInt8PtrTy(Ctx));
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Function *F = dyn_cast<Function>(C);
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// Take over the existing function. The frontend emits a weak stub so that the
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// linker knows about the symbol; this pass replaces the function body.
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F->deleteBody();
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F->setAlignment(4096);
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auto args = F->arg_begin();
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Value &CallSiteTypeId = *(args++);
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CallSiteTypeId.setName("CallSiteTypeId");
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Value &Addr = *(args++);
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Addr.setName("Addr");
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Value &CFICheckFailData = *(args++);
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CFICheckFailData.setName("CFICheckFailData");
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assert(args == F->arg_end());
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BasicBlock *BB = BasicBlock::Create(Ctx, "entry", F);
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BasicBlock *ExitBB = BasicBlock::Create(Ctx, "exit", F);
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BasicBlock *TrapBB = BasicBlock::Create(Ctx, "fail", F);
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IRBuilder<> IRBFail(TrapBB);
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Constant *CFICheckFailFn = M.getOrInsertFunction(
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"__cfi_check_fail", Type::getVoidTy(Ctx), Type::getInt8PtrTy(Ctx),
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Type::getInt8PtrTy(Ctx));
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IRBFail.CreateCall(CFICheckFailFn, {&CFICheckFailData, &Addr});
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IRBFail.CreateBr(ExitBB);
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IRBuilder<> IRBExit(ExitBB);
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IRBExit.CreateRetVoid();
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IRBuilder<> IRB(BB);
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SwitchInst *SI = IRB.CreateSwitch(&CallSiteTypeId, TrapBB, TypeIds.size());
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for (uint64_t TypeId : TypeIds) {
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ConstantInt *CaseTypeId = ConstantInt::get(Type::getInt64Ty(Ctx), TypeId);
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BasicBlock *TestBB = BasicBlock::Create(Ctx, "test", F);
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IRBuilder<> IRBTest(TestBB);
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Function *BitsetTestFn = Intrinsic::getDeclaration(&M, Intrinsic::type_test);
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Value *Test = IRBTest.CreateCall(
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BitsetTestFn, {&Addr, MetadataAsValue::get(
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Ctx, ConstantAsMetadata::get(CaseTypeId))});
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BranchInst *BI = IRBTest.CreateCondBr(Test, ExitBB, TrapBB);
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BI->setMetadata(LLVMContext::MD_prof, VeryLikelyWeights);
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SI->addCase(CaseTypeId, TestBB);
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++NumTypeIds;
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}
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}
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bool CrossDSOCFI::runOnModule(Module &M) {
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if (skipModule(M))
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return false;
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VeryLikelyWeights =
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MDBuilder(M.getContext()).createBranchWeights((1U << 20) - 1, 1);
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if (M.getModuleFlag("Cross-DSO CFI") == nullptr)
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return false;
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buildCFICheck(M);
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return true;
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}
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PreservedAnalyses CrossDSOCFIPass::run(Module &M, ModuleAnalysisManager &AM) {
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CrossDSOCFI Impl;
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bool Changed = Impl.runOnModule(M);
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if (!Changed)
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return PreservedAnalyses::all();
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return PreservedAnalyses::none();
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}
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