Add passes for applying SFI sandboxing at the LLVM IR level

lib/Transforms/NaCl/SandboxMemoryAccesses.cpp

+//===- SandboxMemoryAccesses.cpp - Add SFI to memory accesses--------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// XXX
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+// #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/NaCl.h"
+
+using namespace llvm;
+
+namespace {
+  // This is a ModulePass so that XXX...
+  class SandboxMemoryAccesses : public ModulePass {
+    Value *MemBaseVar;
+    Value *MemBase;
+
+    Value *sandboxPtr(Value *Ptr, Instruction *InsertPt);
+    void sandboxOperand(Instruction *Inst, unsigned OpNum);
+    void convertFunc(Function *Func);
+
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    SandboxMemoryAccesses() : ModulePass(ID) {
+      initializeSandboxMemoryAccessesPass(*PassRegistry::getPassRegistry());
+    }
+
+    virtual bool runOnModule(Module &M);
+  };
+}
+
+char SandboxMemoryAccesses::ID = 0;
+INITIALIZE_PASS(SandboxMemoryAccesses, "sandbox-memory-accesses",
+                "Add SFI sandboxing to memory accesses",
+                false, false)
+
+Value *SandboxMemoryAccesses::sandboxPtr(Value *Ptr, Instruction *InsertPt) {
+  if (!MemBase) {
+    Function *Func = InsertPt->getParent()->getParent();
+    Instruction *MemBaseInst = new LoadInst(MemBaseVar, "mem_base");
+    Func->getEntryBlock().getInstList().push_front(MemBaseInst);
+    MemBase = MemBaseInst;
+  }
+
+  Type *I32 = Type::getInt32Ty(InsertPt->getContext());
+  Type *I64 = Type::getInt64Ty(InsertPt->getContext());
+
+  // Look for the pattern produced by ExpandGetElementPtr.
+  // TODO: ExpandGetElementPtr should really put a "nuw" attr on the
+  // add, and we should check for this here.
+  if (IntToPtrInst *Cast = dyn_cast<IntToPtrInst>(Ptr)) {
+    if (BinaryOperator *Op = dyn_cast<BinaryOperator>(Cast->getOperand(0))) {
+      if (Op->getOpcode() == Instruction::Add) {
+        if (ConstantInt *CI = dyn_cast<ConstantInt>(Op->getOperand(1))) {
+          uint64_t Addend = CI->getZExtValue();
+          if (Addend < 0x10000) {
+            Value *ZExt = new ZExtInst(Op->getOperand(0), I64, "", InsertPt);
+            Value *Add1 = BinaryOperator::Create(
+                BinaryOperator::Add, MemBase, ZExt, "", InsertPt);
+            Value *Add2 = BinaryOperator::Create(
+                BinaryOperator::Add, Add1, ConstantInt::get(I64, Addend),
+                "", InsertPt);
+            return new IntToPtrInst(Add2, Ptr->getType(), "", InsertPt);
+          }
+        }
+      }
+    }
+  }
+
+
+  Value *Truncated = new PtrToIntInst(Ptr, I32, "", InsertPt);
+  Value *ZExt = new ZExtInst(Truncated, I64, "", InsertPt);
+  Value *Added = BinaryOperator::Create(BinaryOperator::Add, MemBase, ZExt,
+                                        "", InsertPt);
+  return new IntToPtrInst(Added, Ptr->getType(), "", InsertPt);
+}
+
+void SandboxMemoryAccesses::sandboxOperand(Instruction *Inst, unsigned OpNum) {
+  Inst->setOperand(OpNum, sandboxPtr(Inst->getOperand(OpNum), Inst));
+}
+
+void SandboxMemoryAccesses::convertFunc(Function *Func) {
+  MemBase = NULL;
+  for (Function::iterator BB = Func->begin(), E = Func->end(); BB != E; ++BB) {
+    for (BasicBlock::iterator Inst = BB->begin(), E = BB->end(); Inst != E;
+         ++Inst) {
+      if (isa<LoadInst>(Inst)) {
+        sandboxOperand(Inst, 0);
+      } else if (isa<StoreInst>(Inst)) {
+        sandboxOperand(Inst, 1);
+      } else if (isa<MemCpyInst>(Inst) || isa<MemMoveInst>(Inst)) {
+        sandboxOperand(Inst, 0);
+        sandboxOperand(Inst, 1);
+      } else if (isa<MemSetInst>(Inst)) {
+        sandboxOperand(Inst, 0);
+      }
+    }
+  }
+}
+
+bool SandboxMemoryAccesses::runOnModule(Module &M) {
+  Type *I64 = Type::getInt64Ty(M.getContext());
+  MemBaseVar = M.getOrInsertGlobal("__sfi_memory_base", I64);
+  for (Module::iterator Func = M.begin(), E = M.end(); Func != E; ++Func) {
+    convertFunc(Func);
+  }
+  return true;
+}
+
+ModulePass *llvm::createSandboxMemoryAccessesPass() {
+  return new SandboxMemoryAccesses();
+}