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Code Issues Releases Wiki Activity

Add constants to analysis of hiding extension casts

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This commit is contained in:
caheckman 2020-02-20 14:42:40 -05:00
parent 36aebc2d9b
commit f28c377e9b
4 changed files with 64 additions and 58 deletions
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51
Ghidra/Features/Decompiler/src/decompile/cpp/cast.cc
View file

@ -166,6 +166,57 @@ int4 CastStrategyC::intPromotionType(const Varnode *vn) const
return UNKNOWN_PROMOTION;
}
bool CastStrategyC::isExtensionCastImplied(const PcodeOp *op,const PcodeOp *readOp) const
{
const Varnode *outVn = op->getOut();
if (outVn->isExplicit()) {
}
else {
if (readOp == (PcodeOp *) 0)
return false;
type_metatype metatype = outVn->getHigh()->getType()->getMetatype();
const Varnode *otherVn;
int4 slot;
switch (readOp->code()) {
case CPUI_PTRADD:
break;
case CPUI_INT_ADD:
case CPUI_INT_SUB:
case CPUI_INT_MULT:
case CPUI_INT_DIV:
case CPUI_INT_AND:
case CPUI_INT_OR:
case CPUI_INT_XOR:
case CPUI_INT_EQUAL:
case CPUI_INT_NOTEQUAL:
case CPUI_INT_LESS:
case CPUI_INT_LESSEQUAL:
case CPUI_INT_SLESS:
case CPUI_INT_SLESSEQUAL:
slot = readOp->getSlot(outVn);
otherVn = readOp->getIn(1 - slot);
// Check if the expression involves an explicit variable of the right integer type
if (otherVn->isConstant()) {
// Integer tokens do not naturally indicate their size, and
// integers that are bigger than the promotion size are NOT naturally extended.
if (otherVn->getSize() > promoteSize) // So if the integer is bigger than the promotion size
return false; // The extension cast on the other side must be explicit
}
else if (!otherVn->isExplicit())
return false;
if (otherVn->getHigh()->getType()->getMetatype() != metatype)
return false;
break;
default:
return false;
}
return true; // Everything is integer promotion
}
return false;
}
Datatype *CastStrategyC::castStandard(Datatype *reqtype,Datatype *curtype,
bool care_uint_int,bool care_ptr_uint) const

11
Ghidra/Features/Decompiler/src/decompile/cpp/cast.hh
View file

@ -88,6 +88,16 @@ public:
/// \return \b true if a cast is required before extending
virtual bool checkIntPromotionForExtension(const PcodeOp *op) const=0;
/// \brief Is the given ZEXT/SEXT cast implied by the expression its in?
///
/// We've already determined that the given ZEXT or SEXT op can be viewed as a natural \e cast operation.
/// Determine if the cast is implied by the expression its and doesn't need to be printed.
/// \param op is the given ZEXT or SEXT PcodeOp
/// \param readOp is the PcodeOp consuming the output of the extensions (or null)
/// \return \b true if the op as a cast does not need to be printed
virtual bool isExtensionCastImplied(const PcodeOp *op,const PcodeOp *readOp) const=0;
/// \brief Does there need to be a visible cast between the given data-types
///
/// The cast is from a \e current data-type to an \e expected data-type. NULL is returned
@ -151,6 +161,7 @@ public:
virtual int4 intPromotionType(const Varnode *vn) const;
virtual bool checkIntPromotionForCompare(const PcodeOp *op,int4 slot) const;
virtual bool checkIntPromotionForExtension(const PcodeOp *op) const;
virtual bool isExtensionCastImplied(const PcodeOp *op,const PcodeOp *readOp) const;
virtual Datatype *castStandard(Datatype *reqtype,Datatype *curtype,bool care_uint_int,bool care_ptr_uint) const;
virtual Datatype *arithmeticOutputStandard(const PcodeOp *op);
virtual bool isSubpieceCast(Datatype *outtype,Datatype *intype,uint4 offset) const;

59
Ghidra/Features/Decompiler/src/decompile/cpp/printc.cc
View file

@ -595,7 +595,7 @@ void PrintC::opIntZext(const PcodeOp *op,const PcodeOp *readOp)
{
if (castStrategy->isZextCast(op->getOut()->getHigh()->getType(),op->getIn(0)->getHigh()->getType())) {
if (isExtensionCastImplied(op,readOp))
if (option_hide_exts && castStrategy->isExtensionCastImplied(op,readOp))
opHiddenFunc(op);
else
opTypeCast(op);
@ -608,7 +608,7 @@ void PrintC::opIntSext(const PcodeOp *op,const PcodeOp *readOp)
{
if (castStrategy->isSextCast(op->getOut()->getHigh()->getType(),op->getIn(0)->getHigh()->getType())) {
if (isExtensionCastImplied(op,readOp))
if (option_hide_exts && castStrategy->isExtensionCastImplied(op,readOp))
opHiddenFunc(op);
else
opTypeCast(op);
@ -1282,61 +1282,6 @@ bool PrintC::printCharacterConstant(ostream &s,const Address &addr,int4 charsize
return res;
}
/// \brief Is the given ZEXT/SEXT cast implied by the expression its in
///
/// We know that the given ZEXT or SEXT op can be viewed as a natural \e cast operation.
/// Sometimes such a cast is implied by the expression its in, and the cast itself
/// doesn't need to be printed.
/// \param op is the given ZEXT or SEXT PcodeOp
/// \param readOp is the PcodeOp consuming the output of the extensions (or null)
/// \return \b true if the op as a cast does not need to be printed
bool PrintC::isExtensionCastImplied(const PcodeOp *op,const PcodeOp *readOp) const
{
if (!option_hide_exts)
return false; // If hiding extensions is not on, we must always print extension
const Varnode *outVn = op->getOut();
if (outVn->isExplicit()) {
}
else {
if (readOp == (PcodeOp *) 0)
return false;
type_metatype metatype = outVn->getHigh()->getType()->getMetatype();
const Varnode *otherVn;
int4 slot;
switch (readOp->code()) {
case CPUI_PTRADD:
break;
case CPUI_INT_ADD:
case CPUI_INT_SUB:
case CPUI_INT_MULT:
case CPUI_INT_DIV:
case CPUI_INT_AND:
case CPUI_INT_OR:
case CPUI_INT_XOR:
case CPUI_INT_EQUAL:
case CPUI_INT_NOTEQUAL:
case CPUI_INT_LESS:
case CPUI_INT_LESSEQUAL:
case CPUI_INT_SLESS:
case CPUI_INT_SLESSEQUAL:
slot = readOp->getSlot(outVn);
otherVn = readOp->getIn(1 - slot);
// Check if the expression involves an explicit variable of the right integer type
if (!otherVn->isExplicit() && !otherVn->isConstant())
return false;
if (otherVn->getHigh()->getType()->getMetatype() != metatype)
return false;
break;
default:
return false;
}
return true; // Everything is integer promotion
}
return false;
}
/// \brief Push a single character constant to the RPN stack
///
/// For C, a character constant is usually emitted as the character in single quotes.

1
Ghidra/Features/Decompiler/src/decompile/cpp/printc.hh
View file

@ -159,7 +159,6 @@ protected:
void opHiddenFunc(const PcodeOp *op); ///< Push the given p-code op as a hidden token
static bool hasCharTerminator(uint1 *buffer,int4 size,int4 charsize);
bool printCharacterConstant(ostream &s,const Address &addr,int4 charsize) const;
bool isExtensionCastImplied(const PcodeOp *op,const PcodeOp *readOp) const;
virtual void pushConstant(uintb val,const Datatype *ct,
const Varnode *vn,const PcodeOp *op);
virtual bool pushEquate(uintb val,int4 sz,const EquateSymbol *sym,