[cfe-dev] Proposed: change tracking for RegionStore
Jordy Rose
jediknil at belkadan.com
Mon Aug 9 15:50:47 PDT 2010
On Mon, 9 Aug 2010 13:45:50 -0700, Ted Kremenek <kremenek at apple.com>
wrote:
> On Aug 7, 2010, at 6:42 PM, Jordy Rose wrote:
>
>> Second pass. This mainly addresses the fact that InvalidateRegions
>> doesn't
>> just invalidate the regions it's given -- thanks, Ted -- by recording
all
>> the touched regions in a SmallVector.
>
> Thanks Jordy. I'm still really leery about the cost of this, but I'm
> willing to see how CStringChecker makes use of the information so we can
> see how we can possibly do this better. Recording the entire set of
> invalidated regions seems really expensive.
I know. Probably in most cases, the set won't be very big, but any work to
pare out regions (such as only storing base regions) seems like it'd be
more expensive, and also prone to miss cases where a region without a store
binding is invalidated. (This should still make it back to checkers.)
I've attached my local version of CStringChecker, so you can see how I'm
using all of this. Much of it is very simple usage and can probably be
cleaned up to be more efficient.
As for this:
> virtual Store InvalidateRegions(Store store,
> const MemRegion * const *Begin,
> const MemRegion * const *End,
> const Expr *E, unsigned Count,
> InvalidatedSymbols *IS,
> - bool invalidateGlobals) = 0;
> + bool invalidateGlobals,
> + InvalidatedRegions &Regions) = 0;
>
>
> Does it make sense to pass in a pointer instead of a reference? The
> problem with passing in a reference is that it means we always have to
do
> the work of recording the invalidated MemRegions.
Right. I was uneasy about this, but I think it actually ought to stay.
Why? Any region invalidation should be picked up by the checkers
eventually, or we have a correctness problem. (It's /because/ invalidating
a set of regions might touch other regions that this is necessary -- even
an internal use has no guarantee of a controlled invalidation.)
If you think it's necessary, I'll change it, but I think it may actually
be needed now.
-------------- next part --------------
//= CStringChecker.h - Checks calls to C string functions ----------*- C++ -*-//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines CStringChecker, which is an assortment of checks on calls
// to functions in <string.h>.
//
//===----------------------------------------------------------------------===//
#include "GRExprEngineExperimentalChecks.h"
#include "clang/Checker/BugReporter/BugType.h"
#include "clang/Checker/PathSensitive/CheckerVisitor.h"
#include "clang/Checker/PathSensitive/GRStateTrait.h"
#include "llvm/ADT/StringSwitch.h"
using namespace clang;
namespace {
class CStringChecker : public CheckerVisitor<CStringChecker> {
BugType *BT_Null, *BT_Bounds, *BT_Overlap, *BT_NotCString;
public:
CStringChecker()
: BT_Null(0), BT_Bounds(0), BT_Overlap(0), BT_NotCString(0) {}
static void *getTag() { static int tag; return &tag; }
bool EvalCallExpr(CheckerContext &C, const CallExpr *CE);
void PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS);
void MarkLiveSymbols(const GRState *state, SymbolReaper &SR);
const GRState *EvalRegionChanges(const GRState *state,
const MemRegion * const *Begin,
const MemRegion * const *End,
bool*);
typedef void (CStringChecker::*FnCheck)(CheckerContext &, const CallExpr *);
void EvalMemcpy(CheckerContext &C, const CallExpr *CE);
void EvalMemmove(CheckerContext &C, const CallExpr *CE);
void EvalBcopy(CheckerContext &C, const CallExpr *CE);
void EvalCopyCommon(CheckerContext &C, const GRState *state,
const Expr *Size, const Expr *Source, const Expr *Dest,
bool Restricted = false);
void EvalMemcmp(CheckerContext &C, const CallExpr *CE);
void EvalStrlen(CheckerContext &C, const CallExpr *CE);
// Utility methods
std::pair<const GRState*, const GRState*>
AssumeZero(CheckerContext &C, const GRState *state, SVal V, QualType Ty);
SVal GetCStringLengthForRegion(CheckerContext &C, const GRState *&state,
const Expr *Ex, const MemRegion *MR);
SVal GetCStringLength(CheckerContext &C, const GRState *&state,
const Expr *Ex, SVal Buf);
bool SummarizeRegion(llvm::raw_ostream& os, ASTContext& Ctx,
const MemRegion *MR);
// Re-usable checks
const GRState *CheckNonNull(CheckerContext &C, const GRState *state,
const Expr *S, SVal l);
const GRState *CheckLocation(CheckerContext &C, const GRState *state,
const Expr *S, SVal l);
const GRState *CheckBufferAccess(CheckerContext &C, const GRState *state,
const Expr *Size,
const Expr *FirstBuf,
const Expr *SecondBuf = NULL);
const GRState *CheckOverlap(CheckerContext &C, const GRState *state,
const Expr *Size, const Expr *First,
const Expr *Second);
void EmitOverlapBug(CheckerContext &C, const GRState *state,
const Stmt *First, const Stmt *Second);
};
class CStringLength {
public:
typedef llvm::ImmutableMap<const MemRegion *, SVal> EntryMap;
};
} //end anonymous namespace
namespace clang {
template <>
struct GRStateTrait<CStringLength>
: public GRStatePartialTrait<CStringLength::EntryMap> {
static void *GDMIndex() { return CStringChecker::getTag(); }
};
}
void clang::RegisterCStringChecker(GRExprEngine &Eng) {
Eng.registerCheck(new CStringChecker());
}
//===----------------------------------------------------------------------===//
// Individual checks and utility methods.
//===----------------------------------------------------------------------===//
std::pair<const GRState*, const GRState*>
CStringChecker::AssumeZero(CheckerContext &C, const GRState *state, SVal V,
QualType Ty) {
DefinedSVal *Val = dyn_cast<DefinedSVal>(&V);
if (!Val)
return std::pair<const GRState*, const GRState *>(state, state);
ValueManager &ValMgr = C.getValueManager();
SValuator &SV = ValMgr.getSValuator();
DefinedOrUnknownSVal Zero = ValMgr.makeZeroVal(Ty);
DefinedOrUnknownSVal ValIsZero = SV.EvalEQ(state, *Val, Zero);
return state->Assume(ValIsZero);
}
const GRState *CStringChecker::CheckNonNull(CheckerContext &C,
const GRState *state,
const Expr *S, SVal l) {
// If a previous check has failed, propagate the failure.
if (!state)
return NULL;
const GRState *stateNull, *stateNonNull;
llvm::tie(stateNull, stateNonNull) = AssumeZero(C, state, l, S->getType());
if (stateNull && !stateNonNull) {
ExplodedNode *N = C.GenerateSink(stateNull);
if (!N)
return NULL;
if (!BT_Null)
BT_Null = new BuiltinBug("API",
"Null pointer argument in call to byte string function");
// Generate a report for this bug.
BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Null);
EnhancedBugReport *report = new EnhancedBugReport(*BT,
BT->getDescription(), N);
report->addRange(S->getSourceRange());
report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, S);
C.EmitReport(report);
return NULL;
}
// From here on, assume that the value is non-null.
assert(stateNonNull);
return stateNonNull;
}
// FIXME: This was originally copied from ArrayBoundChecker.cpp. Refactor?
const GRState *CStringChecker::CheckLocation(CheckerContext &C,
const GRState *state,
const Expr *S, SVal l) {
// If a previous check has failed, propagate the failure.
if (!state)
return NULL;
// Check for out of bound array element access.
const MemRegion *R = l.getAsRegion();
if (!R)
return state;
const ElementRegion *ER = dyn_cast<ElementRegion>(R);
if (!ER)
return state;
assert(ER->getValueType(C.getASTContext()) == C.getASTContext().CharTy &&
"CheckLocation should only be called with char* ElementRegions");
// Get the size of the array.
const SubRegion *Super = cast<SubRegion>(ER->getSuperRegion());
ValueManager &ValMgr = C.getValueManager();
SVal Extent = ValMgr.convertToArrayIndex(Super->getExtent(ValMgr));
DefinedOrUnknownSVal Size = cast<DefinedOrUnknownSVal>(Extent);
// Get the index of the accessed element.
DefinedOrUnknownSVal &Idx = cast<DefinedOrUnknownSVal>(ER->getIndex());
const GRState *StInBound = state->AssumeInBound(Idx, Size, true);
const GRState *StOutBound = state->AssumeInBound(Idx, Size, false);
if (StOutBound && !StInBound) {
ExplodedNode *N = C.GenerateSink(StOutBound);
if (!N)
return NULL;
if (!BT_Bounds)
BT_Bounds = new BuiltinBug("Out-of-bound array access",
"Byte string function accesses out-of-bound array element "
"(buffer overflow)");
// FIXME: It would be nice to eventually make this diagnostic more clear,
// e.g., by referencing the original declaration or by saying *why* this
// reference is outside the range.
// Generate a report for this bug.
BuiltinBug *BT = static_cast<BuiltinBug*>(BT_Bounds);
RangedBugReport *report = new RangedBugReport(*BT, BT->getDescription(), N);
report->addRange(S->getSourceRange());
C.EmitReport(report);
return NULL;
}
// Array bound check succeeded. From this point forward the array bound
// should always succeed.
return StInBound;
}
const GRState *CStringChecker::CheckBufferAccess(CheckerContext &C,
const GRState *state,
const Expr *Size,
const Expr *FirstBuf,
const Expr *SecondBuf) {
// If a previous check has failed, propagate the failure.
if (!state)
return NULL;
ValueManager &VM = C.getValueManager();
SValuator &SV = VM.getSValuator();
ASTContext &Ctx = C.getASTContext();
QualType SizeTy = Ctx.getSizeType();
QualType PtrTy = Ctx.getPointerType(Ctx.CharTy);
// Check that the first buffer is non-null.
SVal BufVal = state->getSVal(FirstBuf);
state = CheckNonNull(C, state, FirstBuf, BufVal);
if (!state)
return NULL;
// Get the access length and make sure it is known.
SVal LengthVal = state->getSVal(Size);
NonLoc *Length = dyn_cast<NonLoc>(&LengthVal);
if (!Length)
return state;
// Compute the offset of the last element to be accessed: size-1.
NonLoc One = cast<NonLoc>(VM.makeIntVal(1, SizeTy));
NonLoc LastOffset = cast<NonLoc>(SV.EvalBinOpNN(state, BinaryOperator::Sub,
*Length, One, SizeTy));
// Check that the first buffer is sufficently long.
SVal BufStart = SV.EvalCast(BufVal, PtrTy, FirstBuf->getType());
if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) {
SVal BufEnd = SV.EvalBinOpLN(state, BinaryOperator::Add, *BufLoc,
LastOffset, PtrTy);
state = CheckLocation(C, state, FirstBuf, BufEnd);
// If the buffer isn't large enough, abort.
if (!state)
return NULL;
}
// If there's a second buffer, check it as well.
if (SecondBuf) {
BufVal = state->getSVal(SecondBuf);
state = CheckNonNull(C, state, SecondBuf, BufVal);
if (!state)
return NULL;
BufStart = SV.EvalCast(BufVal, PtrTy, SecondBuf->getType());
if (Loc *BufLoc = dyn_cast<Loc>(&BufStart)) {
SVal BufEnd = SV.EvalBinOpLN(state, BinaryOperator::Add, *BufLoc,
LastOffset, PtrTy);
state = CheckLocation(C, state, SecondBuf, BufEnd);
}
}
// Large enough or not, return this state!
return state;
}
const GRState *CStringChecker::CheckOverlap(CheckerContext &C,
const GRState *state,
const Expr *Size,
const Expr *First,
const Expr *Second) {
// Do a simple check for overlap: if the two arguments are from the same
// buffer, see if the end of the first is greater than the start of the second
// or vice versa.
// If a previous check has failed, propagate the failure.
if (!state)
return NULL;
ValueManager &VM = state->getStateManager().getValueManager();
SValuator &SV = VM.getSValuator();
ASTContext &Ctx = VM.getContext();
const GRState *stateTrue, *stateFalse;
// Get the buffer values and make sure they're known locations.
SVal FirstVal = state->getSVal(First);
SVal SecondVal = state->getSVal(Second);
Loc *FirstLoc = dyn_cast<Loc>(&FirstVal);
if (!FirstLoc)
return state;
Loc *SecondLoc = dyn_cast<Loc>(&SecondVal);
if (!SecondLoc)
return state;
// Are the two values the same?
DefinedOrUnknownSVal EqualTest = SV.EvalEQ(state, *FirstLoc, *SecondLoc);
llvm::tie(stateTrue, stateFalse) = state->Assume(EqualTest);
if (stateTrue && !stateFalse) {
// If the values are known to be equal, that's automatically an overlap.
EmitOverlapBug(C, stateTrue, First, Second);
return NULL;
}
// Assume the two expressions are not equal.
assert(stateFalse);
state = stateFalse;
// Which value comes first?
QualType CmpTy = Ctx.IntTy;
SVal Reverse = SV.EvalBinOpLL(state, BinaryOperator::GT,
*FirstLoc, *SecondLoc, CmpTy);
DefinedOrUnknownSVal *ReverseTest = dyn_cast<DefinedOrUnknownSVal>(&Reverse);
if (!ReverseTest)
return state;
llvm::tie(stateTrue, stateFalse) = state->Assume(*ReverseTest);
if (stateTrue) {
if (stateFalse) {
// If we don't know which one comes first, we can't perform this test.
return state;
} else {
// Switch the values so that FirstVal is before SecondVal.
Loc *tmpLoc = FirstLoc;
FirstLoc = SecondLoc;
SecondLoc = tmpLoc;
// Switch the Exprs as well, so that they still correspond.
const Expr *tmpExpr = First;
First = Second;
Second = tmpExpr;
}
}
// Get the length, and make sure it too is known.
SVal LengthVal = state->getSVal(Size);
NonLoc *Length = dyn_cast<NonLoc>(&LengthVal);
if (!Length)
return state;
// Convert the first buffer's start address to char*.
// Bail out if the cast fails.
QualType CharPtrTy = Ctx.getPointerType(Ctx.CharTy);
SVal FirstStart = SV.EvalCast(*FirstLoc, CharPtrTy, First->getType());
Loc *FirstStartLoc = dyn_cast<Loc>(&FirstStart);
if (!FirstStartLoc)
return state;
// Compute the end of the first buffer. Bail out if THAT fails.
SVal FirstEnd = SV.EvalBinOpLN(state, BinaryOperator::Add,
*FirstStartLoc, *Length, CharPtrTy);
Loc *FirstEndLoc = dyn_cast<Loc>(&FirstEnd);
if (!FirstEndLoc)
return state;
// Is the end of the first buffer past the start of the second buffer?
SVal Overlap = SV.EvalBinOpLL(state, BinaryOperator::GT,
*FirstEndLoc, *SecondLoc, CmpTy);
DefinedOrUnknownSVal *OverlapTest = dyn_cast<DefinedOrUnknownSVal>(&Overlap);
if (!OverlapTest)
return state;
llvm::tie(stateTrue, stateFalse) = state->Assume(*OverlapTest);
if (stateTrue && !stateFalse) {
// Overlap!
EmitOverlapBug(C, stateTrue, First, Second);
return NULL;
}
// Assume the two expressions don't overlap.
assert(stateFalse);
return stateFalse;
}
void CStringChecker::EmitOverlapBug(CheckerContext &C, const GRState *state,
const Stmt *First, const Stmt *Second) {
ExplodedNode *N = C.GenerateSink(state);
if (!N)
return;
if (!BT_Overlap)
BT_Overlap = new BugType("Unix API", "Improper arguments");
// Generate a report for this bug.
RangedBugReport *report =
new RangedBugReport(*BT_Overlap,
"Arguments must not be overlapping buffers", N);
report->addRange(First->getSourceRange());
report->addRange(Second->getSourceRange());
C.EmitReport(report);
}
SVal CStringChecker::GetCStringLengthForRegion(CheckerContext &C,
const GRState *&state,
const Expr *Ex,
const MemRegion *MR) {
// If there's a recorded length, and it's still valid, go ahead and return it.
const SVal *Recorded = state->get<CStringLength>(MR);
if (Recorded)
return *Recorded;
// If the recorded length is not valid, conjure a new value and update
// the state.
unsigned Count = C.getNodeBuilder().getCurrentBlockCount();
ValueManager &ValMgr = C.getValueManager();
QualType SizeTy = ValMgr.getContext().getSizeType();
SVal Strlen = ValMgr.getConjuredSymbolVal(getTag(), Ex, SizeTy, Count);
state = state->set<CStringLength>(MR, Strlen);
return Strlen;
}
SVal CStringChecker::GetCStringLength(CheckerContext &C, const GRState *&state,
const Expr *Ex, SVal Buf) {
const MemRegion *MR = Buf.getAsRegion();
if (!MR) {
// If we can't get a region, see if it's something we /know/ isn't a
// C string. In the context of locations, the only time we can issue such
// a warning is for labels.
if (loc::GotoLabel *Label = dyn_cast<loc::GotoLabel>(&Buf)) {
if (ExplodedNode *N = C.GenerateNode(state)) {
if (!BT_NotCString)
BT_NotCString = new BuiltinBug("API",
"Argument is not a null-terminated string.");
llvm::SmallString<120> buf;
llvm::raw_svector_ostream os(buf);
os << "Argument to byte string function is the address of the label '"
<< Label->getLabel()->getID()->getName()
<< "', which is not a null-terminated string";
// Generate a report for this bug.
EnhancedBugReport *report = new EnhancedBugReport(*BT_NotCString,
os.str(), N);
report->addRange(Ex->getSourceRange());
C.EmitReport(report);
}
return UndefinedVal();
}
// If it's not a region and not a label, give up.
return UnknownVal();
}
// If we have a region, strip casts from it and see if we can figure out
// its length. For anything we can't figure out, just return UnknownVal.
MR = MR->StripCasts();
switch (MR->getKind()) {
case MemRegion::StringRegionKind: {
// Modifying the contents of string regions is undefined [C99 6.4.5p6],
// so we can assume that the byte length is the correct C string length.
ValueManager &ValMgr = C.getValueManager();
QualType SizeTy = ValMgr.getContext().getSizeType();
const StringLiteral *Str = cast<StringRegion>(MR)->getStringLiteral();
return ValMgr.makeIntVal(Str->getByteLength(), SizeTy);
}
case MemRegion::SymbolicRegionKind:
case MemRegion::AllocaRegionKind:
case MemRegion::VarRegionKind:
case MemRegion::FieldRegionKind:
case MemRegion::ObjCIvarRegionKind:
return GetCStringLengthForRegion(C, state, Ex, MR);
case MemRegion::CompoundLiteralRegionKind:
// FIXME: Can we track this? Is it necessary?
return UnknownVal();
case MemRegion::ElementRegionKind:
// FIXME: How can we handle this? It's not good enough to subtract the
// offset from the base string length; consider "123\x00567" and &a[5].
return UnknownVal();
default:
// Other regions (mostly non-data) can't have a reliable C string length.
// In this case, an error is emitted and UndefinedVal is returned.
// The caller should always be prepared to handle this case.
if (ExplodedNode *N = C.GenerateNode(state)) {
if (!BT_NotCString)
BT_NotCString = new BuiltinBug("API",
"Argument is not a null-terminated string.");
llvm::SmallString<120> buf;
llvm::raw_svector_ostream os(buf);
os << "Argument to byte string function is ";
if (SummarizeRegion(os, C.getASTContext(), MR))
os << ", which is not a null-terminated string";
else
os << "not a null-terminated string";
// Generate a report for this bug.
EnhancedBugReport *report = new EnhancedBugReport(*BT_NotCString,
os.str(), N);
report->addRange(Ex->getSourceRange());
C.EmitReport(report);
}
return UndefinedVal();
}
}
bool CStringChecker::SummarizeRegion(llvm::raw_ostream& os, ASTContext& Ctx,
const MemRegion *MR) {
const TypedRegion *TR = dyn_cast<TypedRegion>(MR);
if (!TR)
return false;
switch (TR->getKind()) {
case MemRegion::FunctionTextRegionKind: {
const FunctionDecl *FD = cast<FunctionTextRegion>(TR)->getDecl();
if (FD)
os << "the address of the function '" << FD << "'";
else
os << "the address of a function";
return true;
}
case MemRegion::BlockTextRegionKind:
os << "block text";
return true;
case MemRegion::BlockDataRegionKind:
os << "a block";
return true;
case MemRegion::CXXThisRegionKind:
case MemRegion::CXXObjectRegionKind:
os << "a C++ object of type "
<< TR->getValueType(Ctx).getAsString();
return true;
case MemRegion::VarRegionKind:
os << "a variable of type"
<< TR->getValueType(Ctx).getAsString();
return true;
case MemRegion::FieldRegionKind:
os << "a field of type "
<< TR->getValueType(Ctx).getAsString();
return true;
case MemRegion::ObjCIvarRegionKind:
os << "an instance variable of type "
<< TR->getValueType(Ctx).getAsString();
return true;
default:
return false;
}
}
//===----------------------------------------------------------------------===//
// Evaluation of individual function calls.
//===----------------------------------------------------------------------===//
void CStringChecker::EvalCopyCommon(CheckerContext &C, const GRState *state,
const Expr *Size, const Expr *Dest,
const Expr *Source, bool Restricted) {
// See if the size argument is zero.
SVal SizeVal = state->getSVal(Size);
QualType SizeTy = Size->getType();
const GRState *StZeroSize, *StNonZeroSize;
llvm::tie(StZeroSize, StNonZeroSize) = AssumeZero(C, state, SizeVal, SizeTy);
// If the size is zero, there won't be any actual memory access.
if (StZeroSize)
C.addTransition(StZeroSize);
// If the size can be nonzero, we have to check the other arguments.
if (StNonZeroSize) {
state = StNonZeroSize;
state = CheckBufferAccess(C, state, Size, Dest, Source);
if (Restricted)
state = CheckOverlap(C, state, Size, Dest, Source);
if (state)
C.addTransition(state);
}
}
void CStringChecker::EvalMemcpy(CheckerContext &C, const CallExpr *CE) {
// void *memcpy(void *restrict dst, const void *restrict src, size_t n);
// The return value is the address of the destination buffer.
const Expr *Dest = CE->getArg(0);
const GRState *state = C.getState();
state = state->BindExpr(CE, state->getSVal(Dest));
EvalCopyCommon(C, state, CE->getArg(2), Dest, CE->getArg(1), true);
}
void CStringChecker::EvalMemmove(CheckerContext &C, const CallExpr *CE) {
// void *memmove(void *dst, const void *src, size_t n);
// The return value is the address of the destination buffer.
const Expr *Dest = CE->getArg(0);
const GRState *state = C.getState();
state = state->BindExpr(CE, state->getSVal(Dest));
EvalCopyCommon(C, state, CE->getArg(2), Dest, CE->getArg(1));
}
void CStringChecker::EvalBcopy(CheckerContext &C, const CallExpr *CE) {
// void bcopy(const void *src, void *dst, size_t n);
EvalCopyCommon(C, C.getState(), CE->getArg(2), CE->getArg(1), CE->getArg(0));
}
void CStringChecker::EvalMemcmp(CheckerContext &C, const CallExpr *CE) {
// int memcmp(const void *s1, const void *s2, size_t n);
const Expr *Left = CE->getArg(0);
const Expr *Right = CE->getArg(1);
const Expr *Size = CE->getArg(2);
const GRState *state = C.getState();
ValueManager &ValMgr = C.getValueManager();
SValuator &SV = ValMgr.getSValuator();
// See if the size argument is zero.
SVal SizeVal = state->getSVal(Size);
QualType SizeTy = Size->getType();
const GRState *StZeroSize, *StNonZeroSize;
llvm::tie(StZeroSize, StNonZeroSize) = AssumeZero(C, state, SizeVal, SizeTy);
// If the size can be zero, the result will be 0 in that case, and we don't
// have to check either of the buffers.
if (StZeroSize) {
state = StZeroSize;
state = state->BindExpr(CE, ValMgr.makeZeroVal(CE->getType()));
C.addTransition(state);
}
// If the size can be nonzero, we have to check the other arguments.
if (StNonZeroSize) {
state = StNonZeroSize;
// If we know the two buffers are the same, we know the result is 0.
// First, get the two buffers' addresses. Another checker will have already
// made sure they're not undefined.
DefinedOrUnknownSVal LV = cast<DefinedOrUnknownSVal>(state->getSVal(Left));
DefinedOrUnknownSVal RV = cast<DefinedOrUnknownSVal>(state->getSVal(Right));
// See if they are the same.
DefinedOrUnknownSVal SameBuf = SV.EvalEQ(state, LV, RV);
const GRState *StSameBuf, *StNotSameBuf;
llvm::tie(StSameBuf, StNotSameBuf) = state->Assume(SameBuf);
// If the two arguments might be the same buffer, we know the result is zero,
// and we only need to check one size.
if (StSameBuf) {
state = StSameBuf;
state = CheckBufferAccess(C, state, Size, Left);
if (state) {
state = StSameBuf->BindExpr(CE, ValMgr.makeZeroVal(CE->getType()));
C.addTransition(state);
}
}
// If the two arguments might be different buffers, we have to check the
// size of both of them.
if (StNotSameBuf) {
state = StNotSameBuf;
state = CheckBufferAccess(C, state, Size, Left, Right);
if (state) {
// The return value is the comparison result, which we don't know.
unsigned Count = C.getNodeBuilder().getCurrentBlockCount();
SVal CmpV = ValMgr.getConjuredSymbolVal(NULL, CE, CE->getType(), Count);
state = state->BindExpr(CE, CmpV);
C.addTransition(state);
}
}
}
}
void CStringChecker::EvalStrlen(CheckerContext &C, const CallExpr *CE) {
// size_t strlen(const char *s);
const GRState *state = C.getState();
const Expr *Arg = CE->getArg(0);
SVal ArgVal = state->getSVal(Arg);
// Check that the argument is non-null.
state = CheckNonNull(C, state, Arg, ArgVal);
if (state) {
SVal StrLen = GetCStringLength(C, state, Arg, ArgVal);
// If the argument isn't a valid C string, there's no valid state to
// transition to.
if (StrLen.isUndef())
return;
// If GetCStringLength couldn't figure out the length, conjure a return
// value, so it can be used in constraints, at least.
if (StrLen.isUnknown()) {
ValueManager &ValMgr = C.getValueManager();
unsigned Count = C.getNodeBuilder().getCurrentBlockCount();
StrLen = ValMgr.getConjuredSymbolVal(NULL, CE, CE->getType(), Count);
}
// Bind the return value.
state = state->BindExpr(CE, StrLen);
C.addTransition(state);
}
}
//===----------------------------------------------------------------------===//
// The driver methods.
//===----------------------------------------------------------------------===//
bool CStringChecker::EvalCallExpr(CheckerContext &C, const CallExpr *CE) {
// Get the callee. All the functions we care about are C functions
// with simple identifiers.
const GRState *state = C.getState();
const Expr *Callee = CE->getCallee();
const FunctionDecl *FD = state->getSVal(Callee).getAsFunctionDecl();
if (!FD)
return false;
// Get the name of the callee. If it's a builtin, strip off the prefix.
llvm::StringRef Name = FD->getName();
if (Name.startswith("__builtin_"))
Name = Name.substr(10);
FnCheck EvalFunction = llvm::StringSwitch<FnCheck>(Name)
.Cases("memcpy", "__memcpy_chk", &CStringChecker::EvalMemcpy)
.Cases("memcmp", "bcmp", &CStringChecker::EvalMemcmp)
.Cases("memmove", "__memmove_chk", &CStringChecker::EvalMemmove)
.Case("strlen", &CStringChecker::EvalStrlen)
.Case("bcopy", &CStringChecker::EvalBcopy)
.Default(NULL);
// If the callee isn't a string function, let another checker handle it.
if (!EvalFunction)
return false;
// Check and evaluate the call.
(this->*EvalFunction)(C, CE);
return true;
}
void CStringChecker::PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS) {
// Record string length for char a[] = "abc";
const GRState *state = C.getState();
for (DeclStmt::const_decl_iterator I = DS->decl_begin(), E = DS->decl_end();
I != E; ++I) {
const VarDecl *D = dyn_cast<VarDecl>(*I);
if (!D)
continue;
// FIXME: Handle array fields of structs.
if (!D->getType()->isArrayType())
continue;
const Expr *Init = D->getInit();
if (!Init)
continue;
if (!isa<StringLiteral>(Init))
continue;
Loc VarLoc = state->getLValue(D, C.getPredecessor()->getLocationContext());
DefinedOrUnknownSVal VarLen
= cast<DefinedOrUnknownSVal>(GetCStringLength(C, state, NULL, VarLoc));
SVal StrVal = state->getSVal(Init);
assert(StrVal.isValid() && "Initializer string is unknown or undefined");
DefinedOrUnknownSVal StrLen
= cast<DefinedOrUnknownSVal>(GetCStringLength(C, state, Init, StrVal));
SValuator &SV = C.getSValuator();
DefinedOrUnknownSVal LengthFromString = SV.EvalEQ(state, VarLen, StrLen);
state = state->Assume(LengthFromString, true);
}
C.addTransition(state);
}
const GRState *CStringChecker::EvalRegionChanges(const GRState *state,
const MemRegion * const *Begin,
const MemRegion * const *End,
bool *) {
llvm::SmallPtrSet<const MemRegion *, 8> SuperRegions;
for ( ; Begin != End; ++Begin) {
// Get the entry map. We do this every loop to take invalidations into
// account.
CStringLength::EntryMap Entries = state->get<CStringLength>();
// If there are no entries, bail out.
if (Entries.isEmpty())
break;
// First build a list of the changed region's super-regions.
const MemRegion *MR = *Begin;
SuperRegions.clear();
SuperRegions.insert(MR);
const MemRegion *Super = MR;
while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) {
Super = SR->getSuperRegion();
SuperRegions.insert(Super);
}
// Then loop over the entries in the current state.
for (CStringLength::EntryMap::iterator I = Entries.begin(),
E = Entries.end(); I != E; ++I) {
MR = I.getKey();
// Is this entry for a super-region of the changed region?
if (SuperRegions.count(MR)) {
state = state->remove<CStringLength>(MR);
continue;
}
// Is this entry for a sub-region of the changed region?
Super = MR;
while (const SubRegion *SR = dyn_cast<SubRegion>(Super)) {
Super = SR->getSuperRegion();
if (Super == *Begin) {
state = state->remove<CStringLength>(MR);
break;
}
}
}
}
return state;
}
void CStringChecker::MarkLiveSymbols(const GRState *state, SymbolReaper &SR) {
// Mark all symbols in our string length map as valid.
CStringLength::EntryMap Entries = state->get<CStringLength>();
for (CStringLength::EntryMap::iterator I = Entries.begin(), E = Entries.end();
I != E; ++I) {
SVal Len = I.getData();
for (SVal::symbol_iterator SI = Len.symbol_begin(), SE = Len.symbol_end();
SI != SE; ++SI) {
SR.markLive(*SI);
}
}
}
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