SValBuilder.cpp revision 7f1fd2f182717d5ce6cde60398128910c90f98be
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 227Optional<SVal> SValBuilder::getConstantVal(const Expr *E) { 228 E = E->IgnoreParens(); 229 230 switch (E->getStmtClass()) { 231 // Handle expressions that we treat differently from the AST's constant 232 // evaluator. 233 case Stmt::AddrLabelExprClass: 234 return makeLoc(cast<AddrLabelExpr>(E)); 235 236 case Stmt::CXXScalarValueInitExprClass: 237 case Stmt::ImplicitValueInitExprClass: 238 return makeZeroVal(E->getType()); 239 240 case Stmt::ObjCStringLiteralClass: { 241 const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E); 242 return makeLoc(getRegionManager().getObjCStringRegion(SL)); 243 } 244 245 case Stmt::StringLiteralClass: { 246 const StringLiteral *SL = cast<StringLiteral>(E); 247 return makeLoc(getRegionManager().getStringRegion(SL)); 248 } 249 250 // Fast-path some expressions to avoid the overhead of going through the AST's 251 // constant evaluator 252 case Stmt::CharacterLiteralClass: { 253 const CharacterLiteral *C = cast<CharacterLiteral>(E); 254 return makeIntVal(C->getValue(), C->getType()); 255 } 256 257 case Stmt::CXXBoolLiteralExprClass: 258 return makeBoolVal(cast<CXXBoolLiteralExpr>(E)); 259 260 case Stmt::IntegerLiteralClass: 261 return makeIntVal(cast<IntegerLiteral>(E)); 262 263 case Stmt::ObjCBoolLiteralExprClass: 264 return makeBoolVal(cast<ObjCBoolLiteralExpr>(E)); 265 266 case Stmt::CXXNullPtrLiteralExprClass: 267 return makeNull(); 268 269 // If we don't have a special case, fall back to the AST's constant evaluator. 270 default: { 271 // Don't try to come up with a value for materialized temporaries. 272 if (E->isGLValue()) 273 return None; 274 275 ASTContext &Ctx = getContext(); 276 llvm::APSInt Result; 277 if (E->EvaluateAsInt(Result, Ctx)) 278 return makeIntVal(Result); 279 280 if (Loc::isLocType(E->getType())) 281 if (E->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull)) 282 return makeNull(); 283 284 return None; 285 } 286 } 287} 288 289//===----------------------------------------------------------------------===// 290 291SVal SValBuilder::makeSymExprValNN(ProgramStateRef State, 292 BinaryOperator::Opcode Op, 293 NonLoc LHS, NonLoc RHS, 294 QualType ResultTy) { 295 if (!State->isTainted(RHS) && !State->isTainted(LHS)) 296 return UnknownVal(); 297 298 const SymExpr *symLHS = LHS.getAsSymExpr(); 299 const SymExpr *symRHS = RHS.getAsSymExpr(); 300 // TODO: When the Max Complexity is reached, we should conjure a symbol 301 // instead of generating an Unknown value and propagate the taint info to it. 302 const unsigned MaxComp = 10000; // 100000 28X 303 304 if (symLHS && symRHS && 305 (symLHS->computeComplexity() + symRHS->computeComplexity()) < MaxComp) 306 return makeNonLoc(symLHS, Op, symRHS, ResultTy); 307 308 if (symLHS && symLHS->computeComplexity() < MaxComp) 309 if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>()) 310 return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy); 311 312 if (symRHS && symRHS->computeComplexity() < MaxComp) 313 if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>()) 314 return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy); 315 316 return UnknownVal(); 317} 318 319 320SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op, 321 SVal lhs, SVal rhs, QualType type) { 322 323 if (lhs.isUndef() || rhs.isUndef()) 324 return UndefinedVal(); 325 326 if (lhs.isUnknown() || rhs.isUnknown()) 327 return UnknownVal(); 328 329 if (Optional<Loc> LV = lhs.getAs<Loc>()) { 330 if (Optional<Loc> RV = rhs.getAs<Loc>()) 331 return evalBinOpLL(state, op, *LV, *RV, type); 332 333 return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type); 334 } 335 336 if (Optional<Loc> RV = rhs.getAs<Loc>()) { 337 // Support pointer arithmetic where the addend is on the left 338 // and the pointer on the right. 339 assert(op == BO_Add); 340 341 // Commute the operands. 342 return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type); 343 } 344 345 return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(), 346 type); 347} 348 349DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state, 350 DefinedOrUnknownSVal lhs, 351 DefinedOrUnknownSVal rhs) { 352 return evalBinOp(state, BO_EQ, lhs, rhs, Context.IntTy) 353 .castAs<DefinedOrUnknownSVal>(); 354} 355 356/// Recursively check if the pointer types are equal modulo const, volatile, 357/// and restrict qualifiers. Also, assume that all types are similar to 'void'. 358/// Assumes the input types are canonical. 359static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy, 360 QualType FromTy) { 361 while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) { 362 Qualifiers Quals1, Quals2; 363 ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1); 364 FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2); 365 366 // Make sure that non cvr-qualifiers the other qualifiers (e.g., address 367 // spaces) are identical. 368 Quals1.removeCVRQualifiers(); 369 Quals2.removeCVRQualifiers(); 370 if (Quals1 != Quals2) 371 return false; 372 } 373 374 // If we are casting to void, the 'From' value can be used to represent the 375 // 'To' value. 376 if (ToTy->isVoidType()) 377 return true; 378 379 if (ToTy != FromTy) 380 return false; 381 382 return true; 383} 384 385// FIXME: should rewrite according to the cast kind. 386SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) { 387 castTy = Context.getCanonicalType(castTy); 388 originalTy = Context.getCanonicalType(originalTy); 389 if (val.isUnknownOrUndef() || castTy == originalTy) 390 return val; 391 392 if (castTy->isBooleanType()) { 393 if (val.isUnknownOrUndef()) 394 return val; 395 if (val.isConstant()) 396 return makeTruthVal(!val.isZeroConstant(), castTy); 397 if (SymbolRef Sym = val.getAsSymbol()) { 398 BasicValueFactory &BVF = getBasicValueFactory(); 399 // FIXME: If we had a state here, we could see if the symbol is known to 400 // be zero, but we don't. 401 return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy); 402 } 403 404 assert(val.getAs<Loc>()); 405 return makeTruthVal(true, castTy); 406 } 407 408 // For const casts, casts to void, just propagate the value. 409 if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType()) 410 if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy), 411 Context.getPointerType(originalTy))) 412 return val; 413 414 // Check for casts from pointers to integers. 415 if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy)) 416 return evalCastFromLoc(val.castAs<Loc>(), castTy); 417 418 // Check for casts from integers to pointers. 419 if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) { 420 if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) { 421 if (const MemRegion *R = LV->getLoc().getAsRegion()) { 422 StoreManager &storeMgr = StateMgr.getStoreManager(); 423 R = storeMgr.castRegion(R, castTy); 424 return R ? SVal(loc::MemRegionVal(R)) : UnknownVal(); 425 } 426 return LV->getLoc(); 427 } 428 return dispatchCast(val, castTy); 429 } 430 431 // Just pass through function and block pointers. 432 if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) { 433 assert(Loc::isLocType(castTy)); 434 return val; 435 } 436 437 // Check for casts from array type to another type. 438 if (const ArrayType *arrayT = 439 dyn_cast<ArrayType>(originalTy.getCanonicalType())) { 440 // We will always decay to a pointer. 441 QualType elemTy = arrayT->getElementType(); 442 val = StateMgr.ArrayToPointer(val.castAs<Loc>(), elemTy); 443 444 // Are we casting from an array to a pointer? If so just pass on 445 // the decayed value. 446 if (castTy->isPointerType() || castTy->isReferenceType()) 447 return val; 448 449 // Are we casting from an array to an integer? If so, cast the decayed 450 // pointer value to an integer. 451 assert(castTy->isIntegralOrEnumerationType()); 452 453 // FIXME: Keep these here for now in case we decide soon that we 454 // need the original decayed type. 455 // QualType elemTy = cast<ArrayType>(originalTy)->getElementType(); 456 // QualType pointerTy = C.getPointerType(elemTy); 457 return evalCastFromLoc(val.castAs<Loc>(), castTy); 458 } 459 460 // Check for casts from a region to a specific type. 461 if (const MemRegion *R = val.getAsRegion()) { 462 // Handle other casts of locations to integers. 463 if (castTy->isIntegralOrEnumerationType()) 464 return evalCastFromLoc(loc::MemRegionVal(R), castTy); 465 466 // FIXME: We should handle the case where we strip off view layers to get 467 // to a desugared type. 468 if (!Loc::isLocType(castTy)) { 469 // FIXME: There can be gross cases where one casts the result of a function 470 // (that returns a pointer) to some other value that happens to fit 471 // within that pointer value. We currently have no good way to 472 // model such operations. When this happens, the underlying operation 473 // is that the caller is reasoning about bits. Conceptually we are 474 // layering a "view" of a location on top of those bits. Perhaps 475 // we need to be more lazy about mutual possible views, even on an 476 // SVal? This may be necessary for bit-level reasoning as well. 477 return UnknownVal(); 478 } 479 480 // We get a symbolic function pointer for a dereference of a function 481 // pointer, but it is of function type. Example: 482 483 // struct FPRec { 484 // void (*my_func)(int * x); 485 // }; 486 // 487 // int bar(int x); 488 // 489 // int f1_a(struct FPRec* foo) { 490 // int x; 491 // (*foo->my_func)(&x); 492 // return bar(x)+1; // no-warning 493 // } 494 495 assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() || 496 originalTy->isBlockPointerType() || castTy->isReferenceType()); 497 498 StoreManager &storeMgr = StateMgr.getStoreManager(); 499 500 // Delegate to store manager to get the result of casting a region to a 501 // different type. If the MemRegion* returned is NULL, this expression 502 // Evaluates to UnknownVal. 503 R = storeMgr.castRegion(R, castTy); 504 return R ? SVal(loc::MemRegionVal(R)) : UnknownVal(); 505 } 506 507 return dispatchCast(val, castTy); 508} 509