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Code Issues Releases Wiki Activity

Adjust casting rules on implied varnodes

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This commit is contained in:
caheckman 2021-09-23 16:10:29 -04:00
parent 1508f3fee8
commit 75cf11634c
3 changed files with 44 additions and 7 deletions
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16
Ghidra/Features/Decompiler/src/decompile/cpp/cast.cc
View file

@ -352,9 +352,13 @@ bool CastStrategyC::isSubpieceCastEndian(Datatype *outtype,Datatype *intype,uint
bool CastStrategyC::isSextCast(Datatype *outtype,Datatype *intype) const
{
if (outtype->getMetatype()!=TYPE_INT) return false;
type_metatype metaout = outtype->getMetatype();
if (metaout != TYPE_UINT && metaout != TYPE_INT)
return false;
type_metatype metain = intype->getMetatype();
if ((metain!=TYPE_INT)&&(metain!=TYPE_UINT)&&(metain!=TYPE_BOOL))
// Casting to larger storage always extends based on signedness of the input data-type
// So the input must be SIGNED in order to treat SEXT as a cast
if ((metain!=TYPE_INT)&&(metain!=TYPE_BOOL))
return false;
return true;
}
@ -362,9 +366,13 @@ bool CastStrategyC::isSextCast(Datatype *outtype,Datatype *intype) const
bool CastStrategyC::isZextCast(Datatype *outtype,Datatype *intype) const
{
if (outtype->getMetatype()!=TYPE_UINT) return false;
type_metatype metaout = outtype->getMetatype();
if (metaout != TYPE_UINT && metaout != TYPE_INT)
return false;
type_metatype metain = intype->getMetatype();
if ((metain!=TYPE_INT)&&(metain!=TYPE_UINT)&&(metain!=TYPE_BOOL))
// Casting to larger storage always extends based on signedness of the input data-type
// So the input must be UNSIGNED in order to treat ZEXT as a cast
if ((metain!=TYPE_UINT)&&(metain!=TYPE_BOOL))
return false;
return true;
}

34
Ghidra/Features/Decompiler/src/decompile/cpp/coreaction.cc
View file

@ -2195,6 +2195,28 @@ bool ActionSetCasts::testStructOffset0(Varnode *vn,Datatype *ct,CastStrategy *ca
return (castStrategy->castStandard(reqtype, curtype, true, true) == (Datatype *)0);
}
/// \brief Test if two data-types are operation identical
///
/// If, at a source code level, a variable with data-type \b ct1 can be
/// legally substituted for another variable with data-type \b ct2, return \b true.
/// The substitution must be allowed for all possible operations the variable
/// may be involved in.
/// \param ct1 is the first data-type
/// \param ct2 is the second data-type
bool ActionSetCasts::isOpIdentical(Datatype *ct1,Datatype *ct2)
{
while((ct1->getMetatype()==TYPE_PTR)&&(ct2->getMetatype()==TYPE_PTR)) {
ct1 = ((const TypePointer *)ct1)->getPtrTo();
ct2 = ((const TypePointer *)ct2)->getPtrTo();
}
while(ct1->getTypedef() != (Datatype *)0)
ct1 = ct1->getTypedef();
while(ct2->getTypedef() != (Datatype *)0)
ct2 = ct2->getTypedef();
return (ct1 == ct2);
}
/// \brief Insert cast to output Varnode type after given PcodeOp if it is necessary
///
/// \param op is the given PcodeOp
@ -2213,7 +2235,15 @@ int4 ActionSetCasts::castOutput(PcodeOp *op,Funcdata &data,CastStrategy *castStr
outvn = op->getOut();
if (outvn->isImplied()) {
// implied varnode must have parse type
if (outvn->getType()->getMetatype() != TYPE_PTR) // If implied varnode has an atomic (non-pointer) type
if (outvn->isTypeLock()) {
PcodeOp *outOp = outvn->loneDescend();
// The Varnode input to a CPUI_RETURN is marked as implied but
// casting should act as if it were explicit
if (outOp == (PcodeOp *)0 || outOp->code() != CPUI_RETURN) {
force = !isOpIdentical(outvn->getType(), tokenct);
}
}
else if (outvn->getType()->getMetatype() != TYPE_PTR) // If implied varnode has an atomic (non-pointer) type
outvn->updateType(tokenct,false,false); // Ignore it in favor of the token type
else if (tokenct->getMetatype() == TYPE_PTR) { // If the token is a pointer AND implied varnode is pointer
outct = ((TypePointer *)outvn->getType())->getPtrTo();
@ -2222,8 +2252,6 @@ int4 ActionSetCasts::castOutput(PcodeOp *op,Funcdata &data,CastStrategy *castStr
if ((meta!=TYPE_ARRAY)&&(meta!=TYPE_STRUCT))
outvn->updateType(tokenct,false,false); // Otherwise ignore it in favor of the token type
}
if (outvn->getType() != tokenct)
force=true; // Make sure not to drop pointer type
}
if (!force) {
outct = outvn->getHigh()->getType(); // Type of result

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

@ -311,6 +311,7 @@ public:
/// immediately.
class ActionSetCasts : public Action {
static bool testStructOffset0(Varnode *vn,Datatype *ct,CastStrategy *castStrategy);
static bool isOpIdentical(Datatype *ct1,Datatype *ct2);
static int4 castOutput(PcodeOp *op,Funcdata &data,CastStrategy *castStrategy);
static int4 castInput(PcodeOp *op,int4 slot,Funcdata &data,CastStrategy *castStrategy);
public: