llvm/llvm/lib/Transforms/Utils/ASanStackFrameLayout.cpp

//===-- ASanStackFrameLayout.cpp - helper for AddressSanitizer ------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Definition of ComputeASanStackFrameLayout (see ASanStackFrameLayout.h).
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/ScopedPrinter.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>

namespace llvm {

// We sort the stack variables by alignment (largest first) to minimize
// unnecessary large gaps due to alignment.
// It is tempting to also sort variables by size so that larger variables
// have larger redzones at both ends. But reordering will make report analysis
// harder, especially when temporary unnamed variables are present.
// So, until we can provide more information (type, line number, etc)
// for the stack variables we avoid reordering them too much.
static inline bool CompareVars(const ASanStackVariableDescription &a,
                               const ASanStackVariableDescription &b) { … }

// We also force minimal alignment for all vars to kMinAlignment so that vars
// with e.g. alignment 1 and alignment 16 do not get reordered by CompareVars.
static const uint64_t kMinAlignment = …;

// We want to add a full redzone after every variable.
// The larger the variable Size the larger is the redzone.
// The resulting frame size is a multiple of Alignment.
static uint64_t VarAndRedzoneSize(uint64_t Size, uint64_t Granularity,
                                  uint64_t Alignment) { … }

ASanStackFrameLayout
ComputeASanStackFrameLayout(SmallVectorImpl<ASanStackVariableDescription> &Vars,
                            uint64_t Granularity, uint64_t MinHeaderSize) { … }

SmallString<64> ComputeASanStackFrameDescription(
    const SmallVectorImpl<ASanStackVariableDescription> &Vars) { … }

SmallVector<uint8_t, 64>
GetShadowBytes(const SmallVectorImpl<ASanStackVariableDescription> &Vars,
               const ASanStackFrameLayout &Layout) { … }

SmallVector<uint8_t, 64> GetShadowBytesAfterScope(
    const SmallVectorImpl<ASanStackVariableDescription> &Vars,
    const ASanStackFrameLayout &Layout) { … }

} // llvm namespace