ghidra/Ghidra/Features/Decompiler/src/decompile/cpp/variable.cc

/* ###
 * IP: GHIDRA
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "variable.hh"
#include "op.hh"
#include "database.hh"

/// The new instance starts off with no associate Symbol and all properties marked as \e dirty.
/// \param vn is the single Varnode member
HighVariable::HighVariable(Varnode *vn)

{
  numMergeClasses = 1;
  highflags = HighVariable::flagsdirty | HighVariable::typedirty | HighVariable::coverdirty;
  flags = 0;
  type = (Datatype *)0;
  symbol = (Symbol *)0;
  symboloffset = -1;
  inst.push_back(vn);
  vn->setHigh( this, numMergeClasses-1 );
}

/// Only update if the cover is marked as \e dirty.
/// Merge the covers of all Varnode instances.
/// This is \b only called by the Merge class which knows when to call it properly.
void HighVariable::updateCover(void) const

{
  if ((highflags & HighVariable::coverdirty)==0) return; // Cover info is upto date
  highflags &= ~HighVariable::coverdirty;

  wholecover.clear();
  if (!inst[0]->hasCover()) return;
  for(int4 i=0;i<inst.size();++i)
    wholecover.merge(*inst[i]->getCover());
}

/// Only update if flags are marked as \e dirty.
/// Generally if any member Varnode possesses the property, \b this HighVariable should
/// inherit it.  The Varnode::typelock field is not set here, but in updateType().
void HighVariable::updateFlags(void) const

{
  vector<Varnode *>::const_iterator iter;
  uint4 fl;

  if ((highflags & HighVariable::flagsdirty)==0) return; // flags are up to date
  fl = 0;
  for(iter=inst.begin();iter!=inst.end();++iter)
    fl |= (*iter)->getFlags();

				// Keep these flags
  flags &= (Varnode::mark | Varnode::typelock);
				// Update all but these
  flags |= fl & ~(Varnode::mark | Varnode::directwrite | Varnode::typelock );
  highflags &= ~HighVariable::flagsdirty; // Clear the dirty flag
}

/// Using Datatype::typeOrder, find the member Varnode with the most specific data-type.
/// \return the representative member
Varnode *HighVariable::getTypeRepresentative(void) const

{
  vector<Varnode *>::const_iterator iter;
  Varnode *vn,*rep;
  
  iter = inst.begin();
  rep = *iter;
  ++iter;
  for(;iter!=inst.end();++iter) {
    vn = *iter;
    if (rep->isTypeLock() != vn->isTypeLock()) {
      if (vn->isTypeLock())
	rep = vn;
    }
    else if (0>vn->getType()->typeOrder(*rep->getType()))
      rep = vn;
  }
  return rep;
}

/// Only update if the data-type is marked as \e dirty.
/// Get the most locked, most specific data-type from member Varnode objects.
void HighVariable::updateType(void) const

{
  Varnode *vn;

  if ((highflags&HighVariable::typedirty)==0) return; // Type is up to date
  vn = getTypeRepresentative();

  type = vn->getType();
				// Update lock flags
  flags &= ~Varnode::typelock;
  if (vn->isTypeLock())
    flags |= Varnode::typelock;
  highflags &= ~HighVariable::typedirty; // Mark type as clean
}

/// Compare two Varnode objects based just on their storage address
/// \param a is the first Varnode to compare
/// \param b is the second Varnode
/// \return \b true if the first Varnode should be ordered before the second
bool HighVariable::compareJustLoc(const Varnode *a,const Varnode *b)

{
  return (a->getAddr() < b->getAddr());
}

/// Given two Varnode (members), sort them based on naming properties:
///  - A Varnode with an assigned name is preferred
///  - An \e unaffected Varnode is preferred
///  - A global Varnode is preferred
///  - An \e input Varnode is preferred
///  - An \e address \e tied Varnode is preferred
///  - A non-temporary Varnode is preferred
///  - A written Varnode is preferred
///  - An earlier Varnode is preferred
///
/// \return \b true if the second Varnode's name would override the first's
bool HighVariable::compareName(Varnode *vn1,Varnode *vn2)

{
  if (vn1->isNameLock()) return false; // Check for namelocks
  if (vn2->isNameLock()) return true;

  if (vn1->isUnaffected() != vn2->isUnaffected()) // Prefer unaffected
    return vn2->isUnaffected();
  if (vn1->isPersist() != vn2->isPersist()) // Prefer persistent
    return vn2->isPersist();
  if (vn1->isInput() != vn2->isInput())	// Prefer an input
    return vn2->isInput();
  if (vn1->isAddrTied() != vn2->isAddrTied()) // Prefer address tied
    return vn2->isAddrTied();

  // Prefer NOT internal
  if ((vn1->getSpace()->getType() != IPTR_INTERNAL)&&
      (vn2->getSpace()->getType() == IPTR_INTERNAL))
    return false;
  if ((vn1->getSpace()->getType() == IPTR_INTERNAL)&&
      (vn2->getSpace()->getType() != IPTR_INTERNAL))
    return true;
  if (vn1->isWritten() != vn2->isWritten()) // Prefer written
    return vn2->isWritten();
  if (!vn1->isWritten())
    return false;
  // Prefer earlier
  if (vn1->getDef()->getTime() != vn2->getDef()->getTime())
    return (vn2->getDef()->getTime() < vn1->getDef()->getTime());
  return false;
}

/// Members are scored based the properties that are most dominating in choosing a name.
/// \return the highest scoring Varnode member
Varnode *HighVariable::getNameRepresentative(void) const

{
  vector<Varnode *>::const_iterator iter;
  Varnode *rep,*vn;

  iter = inst.begin();
  rep = *iter;
  ++iter;
  for(;iter!=inst.end();++iter) {
    vn = *iter;
    if (compareName(rep,vn))
      rep = vn;
  }
  return rep;
}

/// Search for the given Varnode and cut it out of the list, marking all properties as \e dirty.
/// \param vn is the given Varnode member to remove
void HighVariable::remove(Varnode *vn)

{
  vector<Varnode *>::iterator iter;

  iter = lower_bound(inst.begin(),inst.end(),vn,compareJustLoc);
  for(;iter!=inst.end();++iter) {
    if (*iter == vn) {
      inst.erase(iter);
      highflags |= (HighVariable::flagsdirty|HighVariable::coverdirty|HighVariable::typedirty);
      return;
    }
  }
}

/// The lists of members are merged and the other HighVariable is deleted.
/// \param tv2 is the other HighVariable to merge into \b this
/// \param isspeculative is \b true to keep the new members in separate \e merge classes
void HighVariable::merge(HighVariable *tv2,bool isspeculative)

{
  int4 i;

  if (tv2 == this) return;

//   if (isAddrTied() && tv2->isAddrTied()) {
//     if (tied_varnode()->getAddr() != tv2->tied_varnode()->getAddr())
//       throw LowlevelError("Merging different addrtieds");
//   }

  highflags |= (HighVariable::flagsdirty|HighVariable::typedirty);

  if (isspeculative) {
    for(i=0;i<tv2->inst.size();++i) {
      Varnode *vn = tv2->inst[i];
      vn->setHigh(this,vn->getMergeGroup() + numMergeClasses);
    }
    numMergeClasses += tv2->numMergeClasses;
  }
  else {
    if ((numMergeClasses!=1)||(tv2->numMergeClasses!=1))
      throw LowlevelError("Making a non-speculative merge after speculative merges have occurred");
    for(i=0;i<tv2->inst.size();++i) {
      Varnode *vn = tv2->inst[i];
      vn->setHigh(this,vn->getMergeGroup());
    }
  }
  vector<Varnode *> instcopy(inst);
  inst.resize(inst.size()+tv2->inst.size(),(Varnode *)0);
  std::merge(instcopy.begin(),instcopy.end(),tv2->inst.begin(),tv2->inst.end(),inst.begin(),compareJustLoc);
  tv2->inst.clear();

  if (((highflags&HighVariable::coverdirty)==0)&&((tv2->highflags&HighVariable::coverdirty)==0))
    wholecover.merge(tv2->wholecover);
  else
    highflags |= HighVariable::coverdirty;

  delete tv2;
}

/// All Varnode objects are assigned a HighVariable, including those that don't get names like
/// indirect variables, constants, and annotations.  Determine if \b this, as inherited from its
/// member Varnodes, can have a name.
/// \return \b true if \b this can have a name
bool HighVariable::hasName(void) const

{
  bool indirectonly = true;
  for(int4 i=0;i<inst.size();++i) {
    Varnode *vn = inst[i];
    if (!vn->hasCover()) {
      if (inst.size() > 1)
	throw LowlevelError("Non-coverable varnode has been merged");
      return false;
    }
    if (vn->isImplied()) {
      if (inst.size() > 1)
	throw LowlevelError("Implied varnode has been merged");
      return false;
    }
    if (!vn->isIndirectOnly())
      indirectonly = false;
  }
  if (isUnaffected()) {
    if (!isInput()) return false;
    if (indirectonly) return false;
    Varnode *vn = getInputVarnode();
    if (!vn->isIllegalInput()) { // A leftover unaff illegal input gets named
      if (vn->isSpacebase())	// A legal input, unaff, gets named
	return false;		// Unless it is the stackpointer
    }
  }
  return true;
}

/// This should only be called if isAddrTied() returns \b true. If there is no address tied
/// member, this will throw an exception.
/// \return the first address tied member
Varnode *HighVariable::getTiedVarnode(void) const

{
  int4 i;

  for(i=0;i<inst.size();++i)
    if (inst[i]->isAddrTied())
      return inst[i];

  throw LowlevelError("Could not find address-tied varnode");
}

/// This should only be called if isInput() returns \b true. If there is no input
/// member, this will throw an exception.
/// \return the input Varnode member
Varnode *HighVariable::getInputVarnode(void) const

{
  for(int4 i=0;i<inst.size();++i)
    if (inst[i]->isInput())
      return inst[i];
  throw LowlevelError("Could not find input varnode");
}

/// This is generally used for debug purposes.
/// \param s is the output stream
void HighVariable::printInfo(ostream &s) const

{
  vector<Varnode *>::const_iterator viter;
  Varnode *vn;

  updateType();
  if (symbol == (Symbol *)0) {
    s << "Variable: UNNAMED" << endl;
  }
  else {
    s << "Variable: " << symbol->getName();
    if (symboloffset!=-1)
      s << "(partial)";
    s << endl;
  }
  s << "Type: ";
  type->printRaw(s);
  s << "\n\n";
				
  for(viter=inst.begin();viter!=inst.end();++viter) {
    vn = *viter;
    s << dec << vn->getMergeGroup() << ": ";
    vn->printInfo(s);
  }
}

/// Find the index, for use with getInstance(), that will retrieve the given Varnode member
/// \param vn is the given Varnode member
/// \return the index of the member or -1 if it is not a member
int4 HighVariable::instanceIndex(const Varnode *vn) const

{
  int4 i;

  for(i=0;i<inst.size();++i)
    if (inst[i] == vn) return i;

  return -1;
}

// Varnode *HighVariable::findGlobalRep(void) const

// {
//   vector<Varnode *>::const_iterator iter;
//   Varnode *vn = (Varnode *)0;
//   Varnode *vn2;

//   for(iter=inst.begin();iter!=inst.end();++iter) {
//     vn2 = *iter;
//     if (!vn2->getSpace()->globalDiscovery())
//       continue;
//     if (vn==(Varnode *)0)
//       vn = vn2;
//     else {
//       if (vn->getAddr()!=vn2->getAddr()) // Not a consistent address
// 	return (Varnode *)0;
//     }
//   }
//   return vn;
// }