//=== FixedAddressChecker.cpp - Fixed address usage checker ----*- C++ -*--===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This files defines FixedAddressChecker, a builtin checker that checks for
// assignment of a fixed address to a pointer.
// This check corresponds to CWE-587.
//
//===----------------------------------------------------------------------===//

#include "ClangSACheckers.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"

using namespace clang;
using namespace ento;

namespace {
class FixedAddressChecker
  : public Checker< check::PreStmt<BinaryOperator> > {
  mutable std::unique_ptr<BuiltinBug> BT;

public:
  void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const;
};
}

void FixedAddressChecker::checkPreStmt(const BinaryOperator *B,
                                       CheckerContext &C) const {
  // Using a fixed address is not portable because that address will probably
  // not be valid in all environments or platforms.

  if (B->getOpcode() != BO_Assign)
    return;

  QualType T = B->getType();
  if (!T->isPointerType())
    return;

  ProgramStateRef state = C.getState();
  SVal RV = state->getSVal(B->getRHS(), C.getLocationContext());

  if (!RV.isConstant() || RV.isZeroConstant())
    return;

  if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
    if (!BT)
      BT.reset(
          new BuiltinBug(this, "Use fixed address",
                         "Using a fixed address is not portable because that "
                         "address will probably not be valid in all "
                         "environments or platforms."));
    auto R = llvm::make_unique<BugReport>(*BT, BT->getDescription(), N);
    R->addRange(B->getRHS()->getSourceRange());
    C.emitReport(std::move(R));
  }
}

void ento::registerFixedAddressChecker(CheckerManager &mgr) {
  mgr.registerChecker<FixedAddressChecker>();
}
