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128 lines
4.7 KiB
C++
128 lines
4.7 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/Pass.h"
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#include "llvm/Target/TargetLowering.h"
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namespace llvm {
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class DominatorTree;
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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<DominatorTree>();
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}
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SSPLayoutKind getSSPLayout(const AllocaInst *AI) const;
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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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