SafeStack.cpp | Explore in Territory

//===- SafeStack.cpp - Safe Stack Insertion -------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass splits the stack into the safe stack (kept as-is for LLVM backend)
// and the unsafe stack (explicitly allocated and managed through the runtime
// support library).
//
// http://clang.llvm.org/docs/SafeStack.html
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/SafeStack.h"
#include "SafeStackLayout.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/InlineCost.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/StackLifetime.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Use.h"
#include "llvm/IR/Value.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <optional>
#include <string>
#include <utility>

usingnamespacellvm;
usingnamespacellvm::safestack;

#define DEBUG_TYPE …

llvm // namespace llvm

/// Use __safestack_pointer_address even if the platform has a faster way of
/// access safe stack pointer.
static cl::opt<bool>
    SafeStackUsePointerAddress("safestack-use-pointer-address",
                                  cl::init(false), cl::Hidden);

static cl::opt<bool> ClColoring("safe-stack-coloring",
                                cl::desc("enable safe stack coloring"),
                                cl::Hidden, cl::init(true));

namespace {

/// The SafeStack pass splits the stack of each function into the safe
/// stack, which is only accessed through memory safe dereferences (as
/// determined statically), and the unsafe stack, which contains all
/// local variables that are accessed in ways that we can't prove to
/// be safe.
class SafeStack { … };

constexpr Align SafeStack::StackAlignment;

uint64_t SafeStack::getStaticAllocaAllocationSize(const AllocaInst* AI) { … }

bool SafeStack::IsAccessSafe(Value *Addr, uint64_t AccessSize,
                             const Value *AllocaPtr, uint64_t AllocaSize) { … }

bool SafeStack::IsMemIntrinsicSafe(const MemIntrinsic *MI, const Use &U,
                                   const Value *AllocaPtr,
                                   uint64_t AllocaSize) { … }

/// Check whether a given allocation must be put on the safe
/// stack or not. The function analyzes all uses of AI and checks whether it is
/// only accessed in a memory safe way (as decided statically).
bool SafeStack::IsSafeStackAlloca(const Value *AllocaPtr, uint64_t AllocaSize) { … }

Value *SafeStack::getStackGuard(IRBuilder<> &IRB, Function &F) { … }

void SafeStack::findInsts(Function &F,
                          SmallVectorImpl<AllocaInst *> &StaticAllocas,
                          SmallVectorImpl<AllocaInst *> &DynamicAllocas,
                          SmallVectorImpl<Argument *> &ByValArguments,
                          SmallVectorImpl<Instruction *> &Returns,
                          SmallVectorImpl<Instruction *> &StackRestorePoints) { … }

AllocaInst *
SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
                                    ArrayRef<Instruction *> StackRestorePoints,
                                    Value *StaticTop, bool NeedDynamicTop) { … }

void SafeStack::checkStackGuard(IRBuilder<> &IRB, Function &F, Instruction &RI,
                                AllocaInst *StackGuardSlot, Value *StackGuard) { … }

/// We explicitly compute and set the unsafe stack layout for all unsafe
/// static alloca instructions. We save the unsafe "base pointer" in the
/// prologue into a local variable and restore it in the epilogue.
Value *SafeStack::moveStaticAllocasToUnsafeStack(
    IRBuilder<> &IRB, Function &F, ArrayRef<AllocaInst *> StaticAllocas,
    ArrayRef<Argument *> ByValArguments, Instruction *BasePointer,
    AllocaInst *StackGuardSlot) { … }

void SafeStack::moveDynamicAllocasToUnsafeStack(
    Function &F, Value *UnsafeStackPtr, AllocaInst *DynamicTop,
    ArrayRef<AllocaInst *> DynamicAllocas) { … }

bool SafeStack::ShouldInlinePointerAddress(CallInst &CI) { … }

void SafeStack::TryInlinePointerAddress() { … }

bool SafeStack::run() { … }

class SafeStackLegacyPass : public FunctionPass { … };

} // end anonymous namespace

PreservedAnalyses SafeStackPass::run(Function &F,
                                     FunctionAnalysisManager &FAM) { … }

char SafeStackLegacyPass::ID = …;

INITIALIZE_PASS_BEGIN(SafeStackLegacyPass, DEBUG_TYPE,
                      "Safe Stack instrumentation pass", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(SafeStackLegacyPass, DEBUG_TYPE,
                    "Safe Stack instrumentation pass", false, false)

FunctionPass *llvm::createSafeStackPass() { … }
llvm/llvm/lib/CodeGen/SafeStack.cpp
