Add passes for applying SFI sandboxing at the LLVM IR level

lib/Transforms/NaCl/AllocateDataSegment.cpp

+//===- AllocateDataSegment.cpp - Create template for data segment----------===//
+//
+//                     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/Constants.h"
+#include "llvm/IR/DataLayout.h"
+// #include "llvm/IR/Function.h"
+// #include "llvm/IR/Instructions.h"
+// #include "llvm/IR/Intrinsics.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 because it modifies global variables.
+  class AllocateDataSegment : public ModulePass {
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    AllocateDataSegment() : ModulePass(ID) {
+      initializeAllocateDataSegmentPass(*PassRegistry::getPassRegistry());
+    }
+
+    virtual bool runOnModule(Module &M);
+  };
+}
+
+char AllocateDataSegment::ID = 0;
+INITIALIZE_PASS(AllocateDataSegment, "allocate-data-segment",
+                "Create template for data segment",
+                false, false)
+
+bool AllocateDataSegment::runOnModule(Module &M) {
+  Type *I32 = Type::getInt32Ty(M.getContext());
+  Type *IntPtrType = I32; // XXX
+  unsigned BaseAddr = 0x10000;
+
+  SmallVector<Type *, 20> Types;
+  for (Module::global_iterator GV = M.global_begin(), E = M.global_end();
+       GV != E;
+       ++GV) {
+    if (!GV->hasInitializer()) {
+      report_fatal_error(std::string("Variable ") + GV->getName() +
+                         " has no initializer");
+    }
+    Types.push_back(GV->getInitializer()->getType());
+  }
+  StructType *TemplateType = StructType::create(M.getContext(), "data_template");
+  // TODO: add padding manually and set isPacked=true.
+  TemplateType->setBody(Types);
+
+  // In order to handle global variable initializers that refer to other
+  // global variables, this pass cannot delete any global variables yet.
+  Constant *BasePtr = ConstantExpr::getIntToPtr(
+      ConstantInt::get(IntPtrType, BaseAddr),
+      TemplateType->getPointerTo());
+  unsigned Index = 0;
+  for (Module::global_iterator GV = M.global_begin(), E = M.global_end();
+       GV != E;
+       ++GV) {
+    Constant *Indexes[] = {
+      ConstantInt::get(I32, 0),
+      ConstantInt::get(I32, Index)
+    };
+    Value *Ptr = ConstantExpr::getGetElementPtr(BasePtr, Indexes);
+    GV->replaceAllUsesWith(Ptr);
+    Index++;
+  }
+
+  SmallVector<Constant *, 20> Fields;
+  for (Module::global_iterator Iter = M.global_begin(), E = M.global_end();
+       Iter != E; ) {
+    GlobalVariable *GV = Iter++;
+    Fields.push_back(GV->getInitializer());
+    GV->eraseFromParent();
+  }
+  Constant *Template = ConstantStruct::get(TemplateType, Fields);
+  new GlobalVariable(M, TemplateType, /*isConstant=*/true,
+                     GlobalVariable::ExternalLinkage, Template,
+                     "__sfi_data_segment");
+
+  DataLayout DL(&M);
+  Constant *TemplateSize =
+      ConstantInt::get(IntPtrType, DL.getTypeAllocSize(TemplateType));
+  new GlobalVariable(M, TemplateSize->getType(), /*isConstant=*/true,
+                     GlobalVariable::ExternalLinkage, TemplateSize,
+                     "__sfi_data_segment_size");
+
+  return true;
+}
+
+ModulePass *llvm::createAllocateDataSegmentPass() {
+  return new AllocateDataSegment();
+}