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+//===-- ForwardControlFlowIntegrity.h: Forward-Edge CFI ---------*- C++ -*-===//
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass instruments indirect calls with checks to ensure that these calls
+// pass through the appropriate jump-instruction table generated by
+// JumpInstrTables.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_FORWARDCONTROLFLOWINTEGRITY_H
+#define LLVM_CODEGEN_FORWARDCONTROLFLOWINTEGRITY_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetOptions.h"
+
+#include <string>
+
+namespace llvm {
+
+class AnalysisUsage;
+class BasicBlock;
+class Constant;
+class Function;
+class Instruction;
+class Module;
+class Value;
+
+/// ForwardControlFlowIntegrity uses the information from JumpInstrTableInfo to
+/// prepend checks to indirect calls to make sure that these calls target valid
+/// locations.
+class ForwardControlFlowIntegrity : public ModulePass {
+public:
+ static char ID;
+
+ ForwardControlFlowIntegrity();
+ ForwardControlFlowIntegrity(JumpTable::JumpTableType JTT,
+ CFIntegrity CFIType,
+ bool CFIEnforcing, std::string CFIFuncName);
+ ~ForwardControlFlowIntegrity() override;
+
+ /// Runs the CFI pass on a given module. This works best if the module in
+ /// question is the result of link-time optimization (see lib/LTO).
+ bool runOnModule(Module &M) override;
+ const char *getPassName() const override {
+ return "Forward Control-Flow Integrity";
+ }
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+private:
+ typedef SmallVector<Instruction *, 64> CallSet;
+
+ /// A structure that is used to keep track of constant table information.
+ struct CFIConstants {
+ Constant *StartValue;
+ Constant *MaskValue;
+ Constant *Size;
+ };
+
+ /// A map from function type to the base of the table for this type and a mask
+ /// for the table
+ typedef DenseMap<FunctionType *, CFIConstants> CFITables;
+
+ CallSet IndirectCalls;
+
+ /// The type of jumptable implementation.
+ JumpTable::JumpTableType JTType;
+
+ /// The type of CFI check to add before each indirect call.
+ CFIntegrity CFIType;
+
+ /// A value that controls whether or not CFI violations cause a halt.
+ bool CFIEnforcing;
+
+ /// The name of the function to call in case of a CFI violation when
+ /// CFIEnforcing is false. There is a default function that ignores
+ /// violations.
+ std::string CFIFuncName;
+
+ /// The alignment of each entry in the table, from JumpInstrTableInfo. The
+ /// JumpInstrTableInfo class always makes this a power of two.
+ uint64_t ByteAlignment;
+
+ /// The base-2 logarithm of ByteAlignment, needed for some of the transforms
+ /// (like CFIntegrity::Ror)
+ unsigned LogByteAlignment;
+
+ /// Adds checks to each indirect call site to make sure that it is calling a
+ /// function in our jump table.
+ void updateIndirectCalls(Module &M, CFITables &CFIT);
+
+ /// Walks the instructions to find all the indirect calls.
+ void getIndirectCalls(Module &M);
+
+ /// Adds a function that handles violations in non-enforcing mode
+ /// (!CFIEnforcing). The default warning function simply returns, since the
+ /// exact details of how to handle CFI violations depend on the application.
+ void addWarningFunction(Module &M);
+
+ /// Rewrites a function pointer in a call/invoke instruction to force it into
+ /// a table.
+ void rewriteFunctionPointer(Module &M, Instruction *I, Value *FunPtr,
+ Constant *JumpTableStart, Constant *JumpTableMask,
+ Constant *JumpTableSize);
+
+ /// Inserts a check and a call to a warning function at a given instruction
+ /// that must be an indirect call.
+ void insertWarning(Module &M, BasicBlock *Block, Instruction *I,
+ Value *FunPtr);
+};
+
+ModulePass *
+createForwardControlFlowIntegrityPass(JumpTable::JumpTableType JTT,
+ CFIntegrity CFIType,
+ bool CFIEnforcing, StringRef CFIFuncName);
+}
+
+#endif // LLVM_CODEGEN_FORWARDCONTROLFLOWINTEGRITY_H