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cd52a7a381
Apparently, the style needs to be agreed upon first. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240390 91177308-0d34-0410-b5e6-96231b3b80d8
111 lines
4.6 KiB
C++
111 lines
4.6 KiB
C++
//===-- ASanStackFrameLayout.cpp - helper for AddressSanitizer ------------===//
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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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// Definition of ComputeASanStackFrameLayout (see ASanStackFrameLayout.h).
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/MathExtras.h"
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#include <algorithm>
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namespace llvm {
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// We sort the stack variables by alignment (largest first) to minimize
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// unnecessary large gaps due to alignment.
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// It is tempting to also sort variables by size so that larger variables
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// have larger redzones at both ends. But reordering will make report analysis
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// harder, especially when temporary unnamed variables are present.
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// So, until we can provide more information (type, line number, etc)
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// for the stack variables we avoid reordering them too much.
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static inline bool CompareVars(const ASanStackVariableDescription &a,
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const ASanStackVariableDescription &b) {
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return a.Alignment > b.Alignment;
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}
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// We also force minimal alignment for all vars to kMinAlignment so that vars
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// with e.g. alignment 1 and alignment 16 do not get reordered by CompareVars.
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static const size_t kMinAlignment = 16;
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// The larger the variable Size the larger is the redzone.
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// The resulting frame size is a multiple of Alignment.
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static size_t VarAndRedzoneSize(size_t Size, size_t Alignment) {
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size_t Res = 0;
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if (Size <= 4) Res = 16;
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else if (Size <= 16) Res = 32;
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else if (Size <= 128) Res = Size + 32;
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else if (Size <= 512) Res = Size + 64;
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else if (Size <= 4096) Res = Size + 128;
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else Res = Size + 256;
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return RoundUpToAlignment(Res, Alignment);
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}
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void
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ComputeASanStackFrameLayout(SmallVectorImpl<ASanStackVariableDescription> &Vars,
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size_t Granularity, size_t MinHeaderSize,
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ASanStackFrameLayout *Layout) {
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assert(Granularity >= 8 && Granularity <= 64 &&
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(Granularity & (Granularity - 1)) == 0);
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assert(MinHeaderSize >= 16 && (MinHeaderSize & (MinHeaderSize - 1)) == 0 &&
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MinHeaderSize >= Granularity);
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size_t NumVars = Vars.size();
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assert(NumVars > 0);
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for (size_t i = 0; i < NumVars; i++)
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Vars[i].Alignment = std::max(Vars[i].Alignment, kMinAlignment);
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std::stable_sort(Vars.begin(), Vars.end(), CompareVars);
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SmallString<2048> StackDescriptionStorage;
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raw_svector_ostream StackDescription(StackDescriptionStorage);
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StackDescription << NumVars;
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Layout->FrameAlignment = std::max(Granularity, Vars[0].Alignment);
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SmallVector<uint8_t, 64> &SB(Layout->ShadowBytes);
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SB.clear();
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size_t Offset = std::max(std::max(MinHeaderSize, Granularity),
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Vars[0].Alignment);
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assert((Offset % Granularity) == 0);
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SB.insert(SB.end(), Offset / Granularity, kAsanStackLeftRedzoneMagic);
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for (size_t i = 0; i < NumVars; i++) {
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bool IsLast = i == NumVars - 1;
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size_t Alignment = std::max(Granularity, Vars[i].Alignment);
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(void)Alignment; // Used only in asserts.
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size_t Size = Vars[i].Size;
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const char *Name = Vars[i].Name;
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assert((Alignment & (Alignment - 1)) == 0);
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assert(Layout->FrameAlignment >= Alignment);
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assert((Offset % Alignment) == 0);
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assert(Size > 0);
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StackDescription << " " << Offset << " " << Size << " " << strlen(Name)
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<< " " << Name;
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size_t NextAlignment = IsLast ? Granularity
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: std::max(Granularity, Vars[i + 1].Alignment);
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size_t SizeWithRedzone = VarAndRedzoneSize(Vars[i].Size, NextAlignment);
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SB.insert(SB.end(), Size / Granularity, 0);
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if (Size % Granularity)
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SB.insert(SB.end(), Size % Granularity);
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SB.insert(SB.end(), (SizeWithRedzone - Size) / Granularity,
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IsLast ? kAsanStackRightRedzoneMagic
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: kAsanStackMidRedzoneMagic);
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Vars[i].Offset = Offset;
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Offset += SizeWithRedzone;
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}
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if (Offset % MinHeaderSize) {
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size_t ExtraRedzone = MinHeaderSize - (Offset % MinHeaderSize);
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SB.insert(SB.end(), ExtraRedzone / Granularity,
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kAsanStackRightRedzoneMagic);
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Offset += ExtraRedzone;
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}
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Layout->DescriptionString = StackDescription.str();
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Layout->FrameSize = Offset;
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assert((Layout->FrameSize % MinHeaderSize) == 0);
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assert(Layout->FrameSize / Granularity == Layout->ShadowBytes.size());
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}
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} // llvm namespace
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