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2559070422
string_ostream is a safe and efficient string builder that combines opaque stack storage with a built-in ostream interface. small_string_ostream<bytes> additionally permits an explicit stack storage size other than the default 128 bytes to be provided. Beyond that, storage is transferred to the heap. This convenient class can be used in most places an std::string+raw_string_ostream pair or SmallString<>+raw_svector_ostream pair would previously have been used, in order to guarantee consistent access without byte truncation. The patch also converts much of LLVM to use the new facility. These changes include several probable bug fixes for truncated output, a programming error that's no longer possible with the new interface. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211749 91177308-0d34-0410-b5e6-96231b3b80d8
114 lines
4.6 KiB
C++
114 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 <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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static size_t RoundUpTo(size_t X, size_t RoundTo) {
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assert((RoundTo & (RoundTo - 1)) == 0);
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return (X + RoundTo - 1) & ~(RoundTo - 1);
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}
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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 RoundUpTo(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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small_string_ostream<2048> StackDescription;
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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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