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21befa7761
A pass that adds random noops to X86 binaries to introduce diversity with the goal of increasing security against most return-oriented programming attacks. Command line options: -noop-insertion // Enable noop insertion. -noop-insertion-percentage=X // X% of assembly instructions will have a noop prepended (default: 50%, requires -noop-insertion) -max-noops-per-instruction=X // Randomly generate X noops per instruction. ie. roll the dice X times with probability set above (default: 1). This doesn't guarantee X noop instructions. In addition, the following 'quick switch' in clang enables basic diversity using default settings (currently: noop insertion and schedule randomization; it is intended to be extended in the future). -fdiversify This is the llvm part of the patch. clang part: D3393 http://reviews.llvm.org/D3392 Patch by Stephen Crane (@rinon) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225908 91177308-0d34-0410-b5e6-96231b3b80d8
102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
//===- NoopInsertion.cpp - Noop 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 adds fine-grained diversity by displacing code using randomly
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// placed (optionally target supplied) Noop instructions.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/NoopInsertion.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/Allocator.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/RandomNumberGenerator.h"
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#include "llvm/Target/TargetInstrInfo.h"
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using namespace llvm;
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#define DEBUG_TYPE "noop-insertion"
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static cl::opt<unsigned> NoopInsertionPercentage(
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"noop-insertion-percentage",
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cl::desc("Percentage of instructions that have Noops prepended"),
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cl::init(25)); // Default is a good balance between entropy and
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// performance impact
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static cl::opt<unsigned> MaxNoopsPerInstruction(
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"max-noops-per-instruction",
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llvm::cl::desc("Maximum number of Noops per instruction"),
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llvm::cl::init(1));
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STATISTIC(InsertedNoops,
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"Total number of noop type instructions inserted for diversity");
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char NoopInsertion::ID = 0;
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char &llvm::NoopInsertionID = NoopInsertion::ID;
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INITIALIZE_PASS(NoopInsertion, "noop-insertion",
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"Noop Insertion for fine-grained code randomization", false,
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false)
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NoopInsertion::NoopInsertion() : MachineFunctionPass(ID) {
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initializeNoopInsertionPass(*PassRegistry::getPassRegistry());
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// clamp percentage to 100
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if (NoopInsertionPercentage > 100)
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NoopInsertionPercentage = 100;
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}
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void NoopInsertion::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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bool NoopInsertion::runOnMachineFunction(MachineFunction &Fn) {
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// The RNG must be initialized on first use so we have a Module to
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// construct it from
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if (!RNG)
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RNG.reset(Fn.getFunction()->getParent()->createRNG(this));
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const TargetInstrInfo *TII = Fn.getSubtarget().getInstrInfo();
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unsigned FnInsertedNoopCount = 0;
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for (auto &BB : Fn) {
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MachineBasicBlock::iterator FirstTerm = BB.getFirstTerminator();
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for (MachineBasicBlock::iterator I = BB.begin(), E = BB.end(); I != E;
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++I) {
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if (I->isPseudo())
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continue;
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// Insert random number of Noop-like instructions.
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for (unsigned i = 0; i < MaxNoopsPerInstruction; i++) {
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if (Distribution(*RNG) >= NoopInsertionPercentage)
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continue;
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TII->insertNoop(BB, I, *RNG);
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++FnInsertedNoopCount;
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}
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if (I == FirstTerm)
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break;
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}
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}
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InsertedNoops += FnInsertedNoopCount;
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return FnInsertedNoopCount > 0;
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}
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