SValBuilder.cpp revision 112344ab7f96cf482bce80530676712c282756d5
1// SValBuilder.cpp - Basic class for all SValBuilder implementations -*- C++ -*- 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines SValBuilder, the base class for all (complete) SValBuilder 11// implementations. 12// 13//===----------------------------------------------------------------------===// 14 15#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 16#include "clang/AST/DeclCXX.h" 17#include "clang/AST/ExprCXX.h" 18#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h" 19#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h" 20#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 21#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h" 22 23using namespace clang; 24using namespace ento; 25 26//===----------------------------------------------------------------------===// 27// Basic SVal creation. 28//===----------------------------------------------------------------------===// 29 30void SValBuilder::anchor() { } 31 32DefinedOrUnknownSVal SValBuilder::makeZeroVal(QualType type) { 33 if (Loc::isLocType(type)) 34 return makeNull(); 35 36 if (type->isIntegralOrEnumerationType()) 37 return makeIntVal(0, type); 38 39 // FIXME: Handle floats. 40 // FIXME: Handle structs. 41 return UnknownVal(); 42} 43 44NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op, 45 const llvm::APSInt& rhs, QualType type) { 46 // The Environment ensures we always get a persistent APSInt in 47 // BasicValueFactory, so we don't need to get the APSInt from 48 // BasicValueFactory again. 49 assert(lhs); 50 assert(!Loc::isLocType(type)); 51 return nonloc::SymbolVal(SymMgr.getSymIntExpr(lhs, op, rhs, type)); 52} 53 54NonLoc SValBuilder::makeNonLoc(const llvm::APSInt& lhs, 55 BinaryOperator::Opcode op, const SymExpr *rhs, 56 QualType type) { 57 assert(rhs); 58 assert(!Loc::isLocType(type)); 59 return nonloc::SymbolVal(SymMgr.getIntSymExpr(lhs, op, rhs, type)); 60} 61 62NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op, 63 const SymExpr *rhs, QualType type) { 64 assert(lhs && rhs); 65 assert(!Loc::isLocType(type)); 66 return nonloc::SymbolVal(SymMgr.getSymSymExpr(lhs, op, rhs, type)); 67} 68 69NonLoc SValBuilder::makeNonLoc(const SymExpr *operand, 70 QualType fromTy, QualType toTy) { 71 assert(operand); 72 assert(!Loc::isLocType(toTy)); 73 return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy)); 74} 75 76SVal SValBuilder::convertToArrayIndex(SVal val) { 77 if (val.isUnknownOrUndef()) 78 return val; 79 80 // Common case: we have an appropriately sized integer. 81 if (Optional<nonloc::ConcreteInt> CI = val.getAs<nonloc::ConcreteInt>()) { 82 const llvm::APSInt& I = CI->getValue(); 83 if (I.getBitWidth() == ArrayIndexWidth && I.isSigned()) 84 return val; 85 } 86 87 return evalCastFromNonLoc(val.castAs<NonLoc>(), ArrayIndexTy); 88} 89 90nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){ 91 return makeTruthVal(boolean->getValue()); 92} 93 94DefinedOrUnknownSVal 95SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) { 96 QualType T = region->getValueType(); 97 98 if (!SymbolManager::canSymbolicate(T)) 99 return UnknownVal(); 100 101 SymbolRef sym = SymMgr.getRegionValueSymbol(region); 102 103 if (Loc::isLocType(T)) 104 return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym)); 105 106 return nonloc::SymbolVal(sym); 107} 108 109DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *SymbolTag, 110 const Expr *Ex, 111 const LocationContext *LCtx, 112 unsigned Count) { 113 QualType T = Ex->getType(); 114 115 // Compute the type of the result. If the expression is not an R-value, the 116 // result should be a location. 117 QualType ExType = Ex->getType(); 118 if (Ex->isGLValue()) 119 T = LCtx->getAnalysisDeclContext()->getASTContext().getPointerType(ExType); 120 121 return conjureSymbolVal(SymbolTag, Ex, LCtx, T, Count); 122} 123 124DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag, 125 const Expr *expr, 126 const LocationContext *LCtx, 127 QualType type, 128 unsigned count) { 129 if (!SymbolManager::canSymbolicate(type)) 130 return UnknownVal(); 131 132 SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag); 133 134 if (Loc::isLocType(type)) 135 return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym)); 136 137 return nonloc::SymbolVal(sym); 138} 139 140 141DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt, 142 const LocationContext *LCtx, 143 QualType type, 144 unsigned visitCount) { 145 if (!SymbolManager::canSymbolicate(type)) 146 return UnknownVal(); 147 148 SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount); 149 150 if (Loc::isLocType(type)) 151 return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym)); 152 153 return nonloc::SymbolVal(sym); 154} 155 156DefinedOrUnknownSVal 157SValBuilder::getConjuredHeapSymbolVal(const Expr *E, 158 const LocationContext *LCtx, 159 unsigned VisitCount) { 160 QualType T = E->getType(); 161 assert(Loc::isLocType(T)); 162 assert(SymbolManager::canSymbolicate(T)); 163 164 SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount); 165 return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym)); 166} 167 168DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag, 169 const MemRegion *region, 170 const Expr *expr, QualType type, 171 unsigned count) { 172 assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type"); 173 174 SymbolRef sym = 175 SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag); 176 177 if (Loc::isLocType(type)) 178 return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym)); 179 180 return nonloc::SymbolVal(sym); 181} 182 183DefinedOrUnknownSVal 184SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol, 185 const TypedValueRegion *region) { 186 QualType T = region->getValueType(); 187 188 if (!SymbolManager::canSymbolicate(T)) 189 return UnknownVal(); 190 191 SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region); 192 193 if (Loc::isLocType(T)) 194 return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym)); 195 196 return nonloc::SymbolVal(sym); 197} 198 199DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) { 200 return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func)); 201} 202 203DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block, 204 CanQualType locTy, 205 const LocationContext *locContext) { 206 const BlockTextRegion *BC = 207 MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext()); 208 const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext); 209 return loc::MemRegionVal(BD); 210} 211 212/// Return a memory region for the 'this' object reference. 213loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D, 214 const StackFrameContext *SFC) { 215 return loc::MemRegionVal(getRegionManager(). 216 getCXXThisRegion(D->getThisType(getContext()), SFC)); 217} 218 219/// Return a memory region for the 'this' object reference. 220loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D, 221 const StackFrameContext *SFC) { 222 const Type *T = D->getTypeForDecl(); 223 QualType PT = getContext().getPointerType(QualType(T, 0)); 224 return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC)); 225} 226 227//===----------------------------------------------------------------------===// 228 229SVal SValBuilder::makeSymExprValNN(ProgramStateRef State, 230 BinaryOperator::Opcode Op, 231 NonLoc LHS, NonLoc RHS, 232 QualType ResultTy) { 233 if (!State->isTainted(RHS) && !State->isTainted(LHS)) 234 return UnknownVal(); 235 236 const SymExpr *symLHS = LHS.getAsSymExpr(); 237 const SymExpr *symRHS = RHS.getAsSymExpr(); 238 // TODO: When the Max Complexity is reached, we should conjure a symbol 239 // instead of generating an Unknown value and propagate the taint info to it. 240 const unsigned MaxComp = 10000; // 100000 28X 241 242 if (symLHS && symRHS && 243 (symLHS->computeComplexity() + symRHS->computeComplexity()) < MaxComp) 244 return makeNonLoc(symLHS, Op, symRHS, ResultTy); 245 246 if (symLHS && symLHS->computeComplexity() < MaxComp) 247 if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>()) 248 return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy); 249 250 if (symRHS && symRHS->computeComplexity() < MaxComp) 251 if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>()) 252 return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy); 253 254 return UnknownVal(); 255} 256 257 258SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op, 259 SVal lhs, SVal rhs, QualType type) { 260 261 if (lhs.isUndef() || rhs.isUndef()) 262 return UndefinedVal(); 263 264 if (lhs.isUnknown() || rhs.isUnknown()) 265 return UnknownVal(); 266 267 if (Optional<Loc> LV = lhs.getAs<Loc>()) { 268 if (Optional<Loc> RV = rhs.getAs<Loc>()) 269 return evalBinOpLL(state, op, *LV, *RV, type); 270 271 return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type); 272 } 273 274 if (Optional<Loc> RV = rhs.getAs<Loc>()) { 275 // Support pointer arithmetic where the addend is on the left 276 // and the pointer on the right. 277 assert(op == BO_Add); 278 279 // Commute the operands. 280 return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type); 281 } 282 283 return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(), 284 type); 285} 286 287DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state, 288 DefinedOrUnknownSVal lhs, 289 DefinedOrUnknownSVal rhs) { 290 return evalBinOp(state, BO_EQ, lhs, rhs, Context.IntTy) 291 .castAs<DefinedOrUnknownSVal>(); 292} 293 294/// Recursively check if the pointer types are equal modulo const, volatile, 295/// and restrict qualifiers. Also, assume that all types are similar to 'void'. 296/// Assumes the input types are canonical. 297static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy, 298 QualType FromTy) { 299 while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) { 300 Qualifiers Quals1, Quals2; 301 ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1); 302 FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2); 303 304 // Make sure that non cvr-qualifiers the other qualifiers (e.g., address 305 // spaces) are identical. 306 Quals1.removeCVRQualifiers(); 307 Quals2.removeCVRQualifiers(); 308 if (Quals1 != Quals2) 309 return false; 310 } 311 312 // If we are casting to void, the 'From' value can be used to represent the 313 // 'To' value. 314 if (ToTy->isVoidType()) 315 return true; 316 317 if (ToTy != FromTy) 318 return false; 319 320 return true; 321} 322 323// FIXME: should rewrite according to the cast kind. 324SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) { 325 castTy = Context.getCanonicalType(castTy); 326 originalTy = Context.getCanonicalType(originalTy); 327 if (val.isUnknownOrUndef() || castTy == originalTy) 328 return val; 329 330 if (castTy->isBooleanType()) { 331 if (val.isUnknownOrUndef()) 332 return val; 333 if (val.isConstant()) 334 return makeTruthVal(!val.isZeroConstant(), castTy); 335 if (SymbolRef Sym = val.getAsSymbol()) { 336 BasicValueFactory &BVF = getBasicValueFactory(); 337 // FIXME: If we had a state here, we could see if the symbol is known to 338 // be zero, but we don't. 339 return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy); 340 } 341 342 assert(val.getAs<Loc>()); 343 return makeTruthVal(true, castTy); 344 } 345 346 // For const casts, casts to void, just propagate the value. 347 if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType()) 348 if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy), 349 Context.getPointerType(originalTy))) 350 return val; 351 352 // Check for casts from pointers to integers. 353 if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy)) 354 return evalCastFromLoc(val.castAs<Loc>(), castTy); 355 356 // Check for casts from integers to pointers. 357 if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) { 358 if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) { 359 if (const MemRegion *R = LV->getLoc().getAsRegion()) { 360 StoreManager &storeMgr = StateMgr.getStoreManager(); 361 R = storeMgr.castRegion(R, castTy); 362 return R ? SVal(loc::MemRegionVal(R)) : UnknownVal(); 363 } 364 return LV->getLoc(); 365 } 366 return dispatchCast(val, castTy); 367 } 368 369 // Just pass through function and block pointers. 370 if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) { 371 assert(Loc::isLocType(castTy)); 372 return val; 373 } 374 375 // Check for casts from array type to another type. 376 if (originalTy->isArrayType()) { 377 // We will always decay to a pointer. 378 val = StateMgr.ArrayToPointer(val.castAs<Loc>()); 379 380 // Are we casting from an array to a pointer? If so just pass on 381 // the decayed value. 382 if (castTy->isPointerType() || castTy->isReferenceType()) 383 return val; 384 385 // Are we casting from an array to an integer? If so, cast the decayed 386 // pointer value to an integer. 387 assert(castTy->isIntegralOrEnumerationType()); 388 389 // FIXME: Keep these here for now in case we decide soon that we 390 // need the original decayed type. 391 // QualType elemTy = cast<ArrayType>(originalTy)->getElementType(); 392 // QualType pointerTy = C.getPointerType(elemTy); 393 return evalCastFromLoc(val.castAs<Loc>(), castTy); 394 } 395 396 // Check for casts from a region to a specific type. 397 if (const MemRegion *R = val.getAsRegion()) { 398 // Handle other casts of locations to integers. 399 if (castTy->isIntegralOrEnumerationType()) 400 return evalCastFromLoc(loc::MemRegionVal(R), castTy); 401 402 // FIXME: We should handle the case where we strip off view layers to get 403 // to a desugared type. 404 if (!Loc::isLocType(castTy)) { 405 // FIXME: There can be gross cases where one casts the result of a function 406 // (that returns a pointer) to some other value that happens to fit 407 // within that pointer value. We currently have no good way to 408 // model such operations. When this happens, the underlying operation 409 // is that the caller is reasoning about bits. Conceptually we are 410 // layering a "view" of a location on top of those bits. Perhaps 411 // we need to be more lazy about mutual possible views, even on an 412 // SVal? This may be necessary for bit-level reasoning as well. 413 return UnknownVal(); 414 } 415 416 // We get a symbolic function pointer for a dereference of a function 417 // pointer, but it is of function type. Example: 418 419 // struct FPRec { 420 // void (*my_func)(int * x); 421 // }; 422 // 423 // int bar(int x); 424 // 425 // int f1_a(struct FPRec* foo) { 426 // int x; 427 // (*foo->my_func)(&x); 428 // return bar(x)+1; // no-warning 429 // } 430 431 assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() || 432 originalTy->isBlockPointerType() || castTy->isReferenceType()); 433 434 StoreManager &storeMgr = StateMgr.getStoreManager(); 435 436 // Delegate to store manager to get the result of casting a region to a 437 // different type. If the MemRegion* returned is NULL, this expression 438 // Evaluates to UnknownVal. 439 R = storeMgr.castRegion(R, castTy); 440 return R ? SVal(loc::MemRegionVal(R)) : UnknownVal(); 441 } 442 443 return dispatchCast(val, castTy); 444} 445