LLVM  4.0.0
ASanStackFrameLayout.cpp
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1 //===-- ASanStackFrameLayout.cpp - helper for AddressSanitizer ------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Definition of ComputeASanStackFrameLayout (see ASanStackFrameLayout.h).
11 //
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/IR/DebugInfo.h"
19 #include <algorithm>
20 
21 namespace llvm {
22 
23 // We sort the stack variables by alignment (largest first) to minimize
24 // unnecessary large gaps due to alignment.
25 // It is tempting to also sort variables by size so that larger variables
26 // have larger redzones at both ends. But reordering will make report analysis
27 // harder, especially when temporary unnamed variables are present.
28 // So, until we can provide more information (type, line number, etc)
29 // for the stack variables we avoid reordering them too much.
30 static inline bool CompareVars(const ASanStackVariableDescription &a,
32  return a.Alignment > b.Alignment;
33 }
34 
35 // We also force minimal alignment for all vars to kMinAlignment so that vars
36 // with e.g. alignment 1 and alignment 16 do not get reordered by CompareVars.
37 static const size_t kMinAlignment = 16;
38 
39 // The larger the variable Size the larger is the redzone.
40 // The resulting frame size is a multiple of Alignment.
41 static size_t VarAndRedzoneSize(size_t Size, size_t Alignment) {
42  size_t Res = 0;
43  if (Size <= 4) Res = 16;
44  else if (Size <= 16) Res = 32;
45  else if (Size <= 128) Res = Size + 32;
46  else if (Size <= 512) Res = Size + 64;
47  else if (Size <= 4096) Res = Size + 128;
48  else Res = Size + 256;
49  return alignTo(Res, Alignment);
50 }
51 
52 ASanStackFrameLayout
54  size_t Granularity, size_t MinHeaderSize) {
55  assert(Granularity >= 8 && Granularity <= 64 &&
56  (Granularity & (Granularity - 1)) == 0);
57  assert(MinHeaderSize >= 16 && (MinHeaderSize & (MinHeaderSize - 1)) == 0 &&
58  MinHeaderSize >= Granularity);
59  const size_t NumVars = Vars.size();
60  assert(NumVars > 0);
61  for (size_t i = 0; i < NumVars; i++)
62  Vars[i].Alignment = std::max(Vars[i].Alignment, kMinAlignment);
63 
64  std::stable_sort(Vars.begin(), Vars.end(), CompareVars);
65 
66  ASanStackFrameLayout Layout;
67  Layout.Granularity = Granularity;
68  Layout.FrameAlignment = std::max(Granularity, Vars[0].Alignment);
69  size_t Offset = std::max(std::max(MinHeaderSize, Granularity),
70  Vars[0].Alignment);
71  assert((Offset % Granularity) == 0);
72  for (size_t i = 0; i < NumVars; i++) {
73  bool IsLast = i == NumVars - 1;
74  size_t Alignment = std::max(Granularity, Vars[i].Alignment);
75  (void)Alignment; // Used only in asserts.
76  size_t Size = Vars[i].Size;
77  assert((Alignment & (Alignment - 1)) == 0);
78  assert(Layout.FrameAlignment >= Alignment);
79  assert((Offset % Alignment) == 0);
80  assert(Size > 0);
81  size_t NextAlignment = IsLast ? Granularity
82  : std::max(Granularity, Vars[i + 1].Alignment);
83  size_t SizeWithRedzone = VarAndRedzoneSize(Size, NextAlignment);
84  Vars[i].Offset = Offset;
85  Offset += SizeWithRedzone;
86  }
87  if (Offset % MinHeaderSize) {
88  Offset += MinHeaderSize - (Offset % MinHeaderSize);
89  }
90  Layout.FrameSize = Offset;
91  assert((Layout.FrameSize % MinHeaderSize) == 0);
92  return Layout;
93 }
94 
97  SmallString<2048> StackDescriptionStorage;
98  raw_svector_ostream StackDescription(StackDescriptionStorage);
99  StackDescription << Vars.size();
100 
101  for (const auto &Var : Vars) {
102  std::string Name = Var.Name;
103  if (Var.Line) {
104  Name += ":";
105  Name += to_string(Var.Line);
106  }
107  StackDescription << " " << Var.Offset << " " << Var.Size << " "
108  << Name.size() << " " << Name;
109  }
110  return StackDescription.str();
111 }
112 
113 SmallVector<uint8_t, 64>
115  const ASanStackFrameLayout &Layout) {
116  assert(Vars.size() > 0);
118  SB.clear();
119  const size_t Granularity = Layout.Granularity;
120  SB.resize(Vars[0].Offset / Granularity, kAsanStackLeftRedzoneMagic);
121  for (const auto &Var : Vars) {
122  SB.resize(Var.Offset / Granularity, kAsanStackMidRedzoneMagic);
123 
124  SB.resize(SB.size() + Var.Size / Granularity, 0);
125  if (Var.Size % Granularity)
126  SB.push_back(Var.Size % Granularity);
127  }
128  SB.resize(Layout.FrameSize / Granularity, kAsanStackRightRedzoneMagic);
129  return SB;
130 }
131 
134  const ASanStackFrameLayout &Layout) {
136  const size_t Granularity = Layout.Granularity;
137 
138  for (const auto &Var : Vars) {
139  assert(Var.LifetimeSize <= Var.Size);
140  const size_t LifetimeShadowSize =
141  (Var.LifetimeSize + Granularity - 1) / Granularity;
142  const size_t Offset = Var.Offset / Granularity;
143  std::fill(SB.begin() + Offset, SB.begin() + Offset + LifetimeShadowSize,
145  }
146 
147  return SB;
148 }
149 
150 } // llvm namespace
size_t i
static const int kAsanStackMidRedzoneMagic
A raw_ostream that writes to an SmallVector or SmallString.
Definition: raw_ostream.h:490
SmallString< 64 > ComputeASanStackFrameDescription(const SmallVectorImpl< ASanStackVariableDescription > &Vars)
uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew=0)
Returns the next integer (mod 2**64) that is greater than or equal to Value and is a multiple of Alig...
Definition: MathExtras.h:664
static const int kAsanStackLeftRedzoneMagic
static bool CompareVars(const ASanStackVariableDescription &a, const ASanStackVariableDescription &b)
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: APFloat.h:32
SmallVector< uint8_t, 64 > GetShadowBytesAfterScope(const SmallVectorImpl< ASanStackVariableDescription > &Vars, const ASanStackFrameLayout &Layout)
static const int kAsanStackRightRedzoneMagic
INITIALIZE_PASS(HexagonEarlyIfConversion,"hexagon-eif","Hexagon early if conversion", false, false) bool HexagonEarlyIfConversion MachineBasicBlock * SB
static size_t VarAndRedzoneSize(size_t Size, size_t Alignment)
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:115
uint32_t Offset
ASanStackFrameLayout ComputeASanStackFrameLayout(SmallVectorImpl< ASanStackVariableDescription > &Vars, size_t Granularity, size_t MinHeaderSize)
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:843
static const int kAsanStackUseAfterScopeMagic
StringRef str()
Return a StringRef for the vector contents.
Definition: raw_ostream.h:515
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:119
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:135
const std::string to_string(const T &Value)
Definition: ScopedPrinter.h:62
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static const size_t kMinAlignment
SmallVector< uint8_t, 64 > GetShadowBytes(const SmallVectorImpl< ASanStackVariableDescription > &Vars, const ASanStackFrameLayout &Layout)