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StackProtector keeps a ValueMap of alloca instructions to layout kind tags for use by PEI and other later passes. When stack coloring replaces one alloca with a bitcast to another one, the key replacement in this map does not work. Instead, provide an interface to manage this updating directly. This seems like an improvement over the old behavior, where the layout map would not get updated at all when the stack slots were merged. In practice, however, there is likely no observable difference because PEI only did anything special with 'large array' kinds, and if one large array is merged with another, than the replacement should already have been a large array. This is an attempt to unbreak the clang-x86_64-darwin11-RA builder. llvm-svn: 199684
129 lines
4.8 KiB
C++
129 lines
4.8 KiB
C++
//===-- StackProtector.h - Stack Protector Insertion ----------------------===//
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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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// This pass inserts stack protectors into functions which need them. A variable
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// with a random value in it is stored onto the stack before the local variables
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// are allocated. Upon exiting the block, the stored value is checked. If it's
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// changed, then there was some sort of violation and the program aborts.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_STACKPROTECTOR_H
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#define LLVM_CODEGEN_STACKPROTECTOR_H
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Triple.h"
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#include "llvm/ADT/ValueMap.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetLowering.h"
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namespace llvm {
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class Function;
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class Module;
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class PHINode;
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class StackProtector : public FunctionPass {
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public:
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/// SSPLayoutKind. Stack Smashing Protection (SSP) rules require that
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/// vulnerable stack allocations are located close the stack protector.
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enum SSPLayoutKind {
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SSPLK_None, ///< Did not trigger a stack protector. No effect on data
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///< layout.
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SSPLK_LargeArray, ///< Array or nested array >= SSP-buffer-size. Closest
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///< to the stack protector.
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SSPLK_SmallArray, ///< Array or nested array < SSP-buffer-size. 2nd closest
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///< to the stack protector.
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SSPLK_AddrOf ///< The address of this allocation is exposed and
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///< triggered protection. 3rd closest to the protector.
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};
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/// A mapping of AllocaInsts to their required SSP layout.
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typedef ValueMap<const AllocaInst *, SSPLayoutKind> SSPLayoutMap;
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private:
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const TargetMachine *TM;
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/// TLI - Keep a pointer of a TargetLowering to consult for determining
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/// target type sizes.
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const TargetLoweringBase *TLI;
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const Triple Trip;
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Function *F;
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Module *M;
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DominatorTree *DT;
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/// Layout - Mapping of allocations to the required SSPLayoutKind.
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/// StackProtector analysis will update this map when determining if an
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/// AllocaInst triggers a stack protector.
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SSPLayoutMap Layout;
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/// \brief The minimum size of buffers that will receive stack smashing
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/// protection when -fstack-protection is used.
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unsigned SSPBufferSize;
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/// VisitedPHIs - The set of PHI nodes visited when determining
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/// if a variable's reference has been taken. This set
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/// is maintained to ensure we don't visit the same PHI node multiple
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/// times.
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SmallPtrSet<const PHINode *, 16> VisitedPHIs;
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/// InsertStackProtectors - Insert code into the prologue and epilogue of
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/// the function.
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///
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/// - The prologue code loads and stores the stack guard onto the stack.
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/// - The epilogue checks the value stored in the prologue against the
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/// original value. It calls __stack_chk_fail if they differ.
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bool InsertStackProtectors();
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/// CreateFailBB - Create a basic block to jump to when the stack protector
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/// check fails.
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BasicBlock *CreateFailBB();
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/// ContainsProtectableArray - Check whether the type either is an array or
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/// contains an array of sufficient size so that we need stack protectors
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/// for it.
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/// \param [out] IsLarge is set to true if a protectable array is found and
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/// it is "large" ( >= ssp-buffer-size). In the case of a structure with
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/// multiple arrays, this gets set if any of them is large.
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bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
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bool InStruct = false) const;
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/// \brief Check whether a stack allocation has its address taken.
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bool HasAddressTaken(const Instruction *AI);
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/// RequiresStackProtector - Check whether or not this function needs a
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/// stack protector based upon the stack protector level.
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bool RequiresStackProtector();
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public:
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static char ID; // Pass identification, replacement for typeid.
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StackProtector() : FunctionPass(ID), TM(0), TLI(0), SSPBufferSize(0) {
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initializeStackProtectorPass(*PassRegistry::getPassRegistry());
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}
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StackProtector(const TargetMachine *TM)
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: FunctionPass(ID), TM(TM), TLI(0), Trip(TM->getTargetTriple()),
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SSPBufferSize(8) {
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initializeStackProtectorPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addPreserved<DominatorTreeWrapperPass>();
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}
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SSPLayoutKind getSSPLayout(const AllocaInst *AI) const;
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void adjustForColoring(const AllocaInst *From, const AllocaInst *To);
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virtual bool runOnFunction(Function &Fn);
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};
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} // end namespace llvm
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#endif // LLVM_CODEGEN_STACKPROTECTOR_H
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