1 files changed, 114 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/ASanStackFrameLayout.cpp b/lib/Transforms/Utils/ASanStackFrameLayout.cpp
new file mode 100644
index 0000000000000..cce016aafdda9
--- /dev/null
+++ b/lib/Transforms/Utils/ASanStackFrameLayout.cpp
@@ -0,0 +1,114 @@
+//===-- ASanStackFrameLayout.cpp - helper for AddressSanitizer ------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Definition of ComputeASanStackFrameLayout (see ASanStackFrameLayout.h).
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
+#include "llvm/ADT/SmallString.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) {
+  return a.Alignment > b.Alignment;
+}
+
+// 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 size_t kMinAlignment = 16;
+
+static size_t RoundUpTo(size_t X, size_t RoundTo) {
+  assert((RoundTo & (RoundTo - 1)) == 0);
+  return (X + RoundTo - 1) & ~(RoundTo - 1);
+}
+
+// The larger the variable Size the larger is the redzone.
+// The resulting frame size is a multiple of Alignment.
+static size_t VarAndRedzoneSize(size_t Size, size_t Alignment) {
+  size_t Res = 0;
+  if (Size <= 4)  Res = 16;
+  else if (Size <= 16) Res = 32;
+  else if (Size <= 128) Res = Size + 32;
+  else if (Size <= 512) Res = Size + 64;
+  else if (Size <= 4096) Res = Size + 128;
+  else                   Res = Size + 256;
+  return RoundUpTo(Res, Alignment);
+}
+
+void
+ComputeASanStackFrameLayout(SmallVectorImpl<ASanStackVariableDescription> &Vars,
+                            size_t Granularity, size_t MinHeaderSize,
+                            ASanStackFrameLayout *Layout) {
+  assert(Granularity >= 8 && Granularity <= 64 &&
+         (Granularity & (Granularity - 1)) == 0);
+  assert(MinHeaderSize >= 16 && (MinHeaderSize & (MinHeaderSize - 1)) == 0 &&
+         MinHeaderSize >= Granularity);
+  size_t NumVars = Vars.size();
+  assert(NumVars > 0);
+  for (size_t i = 0; i < NumVars; i++)
+    Vars[i].Alignment = std::max(Vars[i].Alignment, kMinAlignment);
+
+  std::stable_sort(Vars.begin(), Vars.end(), CompareVars);
+  SmallString<2048> StackDescriptionStorage;
+  raw_svector_ostream StackDescription(StackDescriptionStorage);
+  StackDescription << NumVars;
+  Layout->FrameAlignment = std::max(Granularity, Vars[0].Alignment);
+  SmallVector<uint8_t, 64> &SB(Layout->ShadowBytes);
+  SB.clear();
+  size_t Offset = std::max(std::max(MinHeaderSize, Granularity),
+     Vars[0].Alignment);
+  assert((Offset % Granularity) == 0);
+  SB.insert(SB.end(), Offset / Granularity, kAsanStackLeftRedzoneMagic);
+  for (size_t i = 0; i < NumVars; i++) {
+    bool IsLast = i == NumVars - 1;
+    size_t Alignment = std::max(Granularity, Vars[i].Alignment);
+    (void)Alignment;  // Used only in asserts.
+    size_t Size = Vars[i].Size;
+    const char *Name = Vars[i].Name;
+    assert((Alignment & (Alignment - 1)) == 0);
+    assert(Layout->FrameAlignment >= Alignment);
+    assert((Offset % Alignment) == 0);
+    assert(Size > 0);
+    StackDescription << " " << Offset << " " << Size << " " << strlen(Name)
+                     << " " << Name;
+    size_t NextAlignment = IsLast ? Granularity
+                   : std::max(Granularity, Vars[i + 1].Alignment);
+    size_t SizeWithRedzone = VarAndRedzoneSize(Vars[i].Size, NextAlignment);
+    SB.insert(SB.end(), Size / Granularity, 0);
+    if (Size % Granularity)
+      SB.insert(SB.end(), Size % Granularity);
+    SB.insert(SB.end(), (SizeWithRedzone - Size) / Granularity,
+        IsLast ? kAsanStackRightRedzoneMagic
+        : kAsanStackMidRedzoneMagic);
+    Vars[i].Offset = Offset;
+    Offset += SizeWithRedzone;
+  }
+  if (Offset % MinHeaderSize) {
+    size_t ExtraRedzone = MinHeaderSize - (Offset % MinHeaderSize);
+    SB.insert(SB.end(), ExtraRedzone / Granularity,
+              kAsanStackRightRedzoneMagic);
+    Offset += ExtraRedzone;
+  }
+  Layout->DescriptionString = StackDescription.str();
+  Layout->FrameSize = Offset;
+  assert((Layout->FrameSize % MinHeaderSize) == 0);
+  assert(Layout->FrameSize / Granularity == Layout->ShadowBytes.size());
+}
+
+} // llvm namespace