xref: /freebsd/contrib/llvm-project/clang/lib/StaticAnalyzer/Checkers/ExprInspectionChecker.cpp (revision 6580f5c38dd5b01aeeaed16b370f1a12423437f0) 
1 //==- ExprInspectionChecker.cpp - Used for regression tests ------*- C++ -*-==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "clang/Analysis/IssueHash.h"
10 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
11 #include "clang/StaticAnalyzer/Checkers/SValExplainer.h"
12 #include "clang/StaticAnalyzer/Checkers/Taint.h"
13 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
14 #include "clang/StaticAnalyzer/Core/Checker.h"
15 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
16 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
18 #include "llvm/ADT/StringSwitch.h"
19 #include "llvm/Support/ScopedPrinter.h"
20 #include <optional>
21 
22 using namespace clang;
23 using namespace ento;
24 
25 namespace {
26 class ExprInspectionChecker
27     : public Checker<eval::Call, check::DeadSymbols, check::EndAnalysis> {
28   const BugType BT{this, "Checking analyzer assumptions", "debug"};
29 
30   // These stats are per-analysis, not per-branch, hence they shouldn't
31   // stay inside the program state.
32   struct ReachedStat {
33     ExplodedNode *ExampleNode;
34     unsigned NumTimesReached;
35   };
36   mutable llvm::DenseMap<const CallExpr *, ReachedStat> ReachedStats;
37 
38   void analyzerEval(const CallExpr *CE, CheckerContext &C) const;
39   void analyzerCheckInlined(const CallExpr *CE, CheckerContext &C) const;
40   void analyzerWarnIfReached(const CallExpr *CE, CheckerContext &C) const;
41   void analyzerNumTimesReached(const CallExpr *CE, CheckerContext &C) const;
42   void analyzerCrash(const CallExpr *CE, CheckerContext &C) const;
43   void analyzerWarnOnDeadSymbol(const CallExpr *CE, CheckerContext &C) const;
44   void analyzerValue(const CallExpr *CE, CheckerContext &C) const;
45   void analyzerDumpSValType(const CallExpr *CE, CheckerContext &C) const;
46   void analyzerDump(const CallExpr *CE, CheckerContext &C) const;
47   void analyzerExplain(const CallExpr *CE, CheckerContext &C) const;
48   void analyzerPrintState(const CallExpr *CE, CheckerContext &C) const;
49   void analyzerGetExtent(const CallExpr *CE, CheckerContext &C) const;
50   void analyzerDumpExtent(const CallExpr *CE, CheckerContext &C) const;
51   void analyzerDumpElementCount(const CallExpr *CE, CheckerContext &C) const;
52   void analyzerHashDump(const CallExpr *CE, CheckerContext &C) const;
53   void analyzerDenote(const CallExpr *CE, CheckerContext &C) const;
54   void analyzerExpress(const CallExpr *CE, CheckerContext &C) const;
55   void analyzerIsTainted(const CallExpr *CE, CheckerContext &C) const;
56 
57   typedef void (ExprInspectionChecker::*FnCheck)(const CallExpr *,
58                                                  CheckerContext &C) const;
59 
60   // Optional parameter `ExprVal` for expression value to be marked interesting.
61   ExplodedNode *reportBug(llvm::StringRef Msg, CheckerContext &C,
62                           std::optional<SVal> ExprVal = std::nullopt) const;
63   ExplodedNode *reportBug(llvm::StringRef Msg, BugReporter &BR, ExplodedNode *N,
64                           std::optional<SVal> ExprVal = std::nullopt) const;
65   template <typename T> void printAndReport(CheckerContext &C, T What) const;
66 
67   const Expr *getArgExpr(const CallExpr *CE, CheckerContext &C) const;
68   const MemRegion *getArgRegion(const CallExpr *CE, CheckerContext &C) const;
69 
70 public:
71   bool evalCall(const CallEvent &Call, CheckerContext &C) const;
72   void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
73   void checkEndAnalysis(ExplodedGraph &G, BugReporter &BR,
74                         ExprEngine &Eng) const;
75 };
76 } // namespace
77 
78 REGISTER_SET_WITH_PROGRAMSTATE(MarkedSymbols, SymbolRef)
79 REGISTER_MAP_WITH_PROGRAMSTATE(DenotedSymbols, SymbolRef, const StringLiteral *)
80 
81 bool ExprInspectionChecker::evalCall(const CallEvent &Call,
82                                      CheckerContext &C) const {
83   const auto *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
84   if (!CE)
85     return false;
86 
87   // These checks should have no effect on the surrounding environment
88   // (globals should not be invalidated, etc), hence the use of evalCall.
89   FnCheck Handler =
90       llvm::StringSwitch<FnCheck>(C.getCalleeName(CE))
91           .Case("clang_analyzer_eval", &ExprInspectionChecker::analyzerEval)
92           .Case("clang_analyzer_checkInlined",
93                 &ExprInspectionChecker::analyzerCheckInlined)
94           .Case("clang_analyzer_crash", &ExprInspectionChecker::analyzerCrash)
95           .Case("clang_analyzer_warnIfReached",
96                 &ExprInspectionChecker::analyzerWarnIfReached)
97           .Case("clang_analyzer_warnOnDeadSymbol",
98                 &ExprInspectionChecker::analyzerWarnOnDeadSymbol)
99           .StartsWith("clang_analyzer_explain",
100                       &ExprInspectionChecker::analyzerExplain)
101           .Case("clang_analyzer_dumpExtent",
102                 &ExprInspectionChecker::analyzerDumpExtent)
103           .Case("clang_analyzer_dumpElementCount",
104                 &ExprInspectionChecker::analyzerDumpElementCount)
105           .Case("clang_analyzer_value", &ExprInspectionChecker::analyzerValue)
106           .StartsWith("clang_analyzer_dumpSvalType",
107                       &ExprInspectionChecker::analyzerDumpSValType)
108           .StartsWith("clang_analyzer_dump",
109                       &ExprInspectionChecker::analyzerDump)
110           .Case("clang_analyzer_getExtent",
111                 &ExprInspectionChecker::analyzerGetExtent)
112           .Case("clang_analyzer_printState",
113                 &ExprInspectionChecker::analyzerPrintState)
114           .Case("clang_analyzer_numTimesReached",
115                 &ExprInspectionChecker::analyzerNumTimesReached)
116           .Case("clang_analyzer_hashDump",
117                 &ExprInspectionChecker::analyzerHashDump)
118           .Case("clang_analyzer_denote", &ExprInspectionChecker::analyzerDenote)
119           .Case("clang_analyzer_express", // This also marks the argument as
120                                           // interesting.
121                 &ExprInspectionChecker::analyzerExpress)
122           .StartsWith("clang_analyzer_isTainted",
123                       &ExprInspectionChecker::analyzerIsTainted)
124           .Default(nullptr);
125 
126   if (!Handler)
127     return false;
128 
129   (this->*Handler)(CE, C);
130   return true;
131 }
132 
133 static const char *getArgumentValueString(const CallExpr *CE,
134                                           CheckerContext &C) {
135   if (CE->getNumArgs() == 0)
136     return "Missing assertion argument";
137 
138   ExplodedNode *N = C.getPredecessor();
139   const LocationContext *LC = N->getLocationContext();
140   ProgramStateRef State = N->getState();
141 
142   const Expr *Assertion = CE->getArg(0);
143   SVal AssertionVal = State->getSVal(Assertion, LC);
144 
145   if (AssertionVal.isUndef())
146     return "UNDEFINED";
147 
148   ProgramStateRef StTrue, StFalse;
149   std::tie(StTrue, StFalse) =
150       State->assume(AssertionVal.castAs<DefinedOrUnknownSVal>());
151 
152   if (StTrue) {
153     if (StFalse)
154       return "UNKNOWN";
155     else
156       return "TRUE";
157   } else {
158     if (StFalse)
159       return "FALSE";
160     else
161       llvm_unreachable("Invalid constraint; neither true or false.");
162   }
163 }
164 
165 ExplodedNode *
166 ExprInspectionChecker::reportBug(llvm::StringRef Msg, CheckerContext &C,
167                                  std::optional<SVal> ExprVal) const {
168   ExplodedNode *N = C.generateNonFatalErrorNode();
169   reportBug(Msg, C.getBugReporter(), N, ExprVal);
170   return N;
171 }
172 
173 ExplodedNode *
174 ExprInspectionChecker::reportBug(llvm::StringRef Msg, BugReporter &BR,
175                                  ExplodedNode *N,
176                                  std::optional<SVal> ExprVal) const {
177   if (!N)
178     return nullptr;
179   auto R = std::make_unique<PathSensitiveBugReport>(BT, Msg, N);
180   if (ExprVal) {
181     R->markInteresting(*ExprVal);
182   }
183   BR.emitReport(std::move(R));
184   return N;
185 }
186 
187 const Expr *ExprInspectionChecker::getArgExpr(const CallExpr *CE,
188                                               CheckerContext &C) const {
189   if (CE->getNumArgs() == 0) {
190     reportBug("Missing argument", C);
191     return nullptr;
192   }
193   return CE->getArg(0);
194 }
195 
196 const MemRegion *ExprInspectionChecker::getArgRegion(const CallExpr *CE,
197                                                      CheckerContext &C) const {
198   const Expr *Arg = getArgExpr(CE, C);
199   if (!Arg)
200     return nullptr;
201 
202   const MemRegion *MR = C.getSVal(Arg).getAsRegion();
203   if (!MR) {
204     reportBug("Cannot obtain the region", C);
205     return nullptr;
206   }
207 
208   return MR;
209 }
210 
211 void ExprInspectionChecker::analyzerEval(const CallExpr *CE,
212                                          CheckerContext &C) const {
213   const LocationContext *LC = C.getPredecessor()->getLocationContext();
214 
215   // A specific instantiation of an inlined function may have more constrained
216   // values than can generally be assumed. Skip the check.
217   if (LC->getStackFrame()->getParent() != nullptr)
218     return;
219 
220   reportBug(getArgumentValueString(CE, C), C);
221 }
222 
223 void ExprInspectionChecker::analyzerWarnIfReached(const CallExpr *CE,
224                                                   CheckerContext &C) const {
225   reportBug("REACHABLE", C);
226 }
227 
228 void ExprInspectionChecker::analyzerNumTimesReached(const CallExpr *CE,
229                                                     CheckerContext &C) const {
230   ++ReachedStats[CE].NumTimesReached;
231   if (!ReachedStats[CE].ExampleNode) {
232     // Later, in checkEndAnalysis, we'd throw a report against it.
233     ReachedStats[CE].ExampleNode = C.generateNonFatalErrorNode();
234   }
235 }
236 
237 void ExprInspectionChecker::analyzerCheckInlined(const CallExpr *CE,
238                                                  CheckerContext &C) const {
239   const LocationContext *LC = C.getPredecessor()->getLocationContext();
240 
241   // An inlined function could conceivably also be analyzed as a top-level
242   // function. We ignore this case and only emit a message (TRUE or FALSE)
243   // when we are analyzing it as an inlined function. This means that
244   // clang_analyzer_checkInlined(true) should always print TRUE, but
245   // clang_analyzer_checkInlined(false) should never actually print anything.
246   if (LC->getStackFrame()->getParent() == nullptr)
247     return;
248 
249   reportBug(getArgumentValueString(CE, C), C);
250 }
251 
252 void ExprInspectionChecker::analyzerExplain(const CallExpr *CE,
253                                             CheckerContext &C) const {
254   const Expr *Arg = getArgExpr(CE, C);
255   if (!Arg)
256     return;
257 
258   SVal V = C.getSVal(Arg);
259   SValExplainer Ex(C.getASTContext());
260   reportBug(Ex.Visit(V), C);
261 }
262 
263 static void printHelper(llvm::raw_svector_ostream &Out, CheckerContext &C,
264                         const llvm::APSInt &I) {
265   Out << I.getBitWidth() << (I.isUnsigned() ? "u:" : "s:");
266   Out << I;
267 }
268 
269 static void printHelper(llvm::raw_svector_ostream &Out, CheckerContext &C,
270                         SymbolRef Sym) {
271   C.getConstraintManager().printValue(Out, C.getState(), Sym);
272 }
273 
274 static void printHelper(llvm::raw_svector_ostream &Out, CheckerContext &C,
275                         SVal V) {
276   Out << V;
277 }
278 
279 template <typename T>
280 void ExprInspectionChecker::printAndReport(CheckerContext &C, T What) const {
281   llvm::SmallString<64> Str;
282   llvm::raw_svector_ostream OS(Str);
283   printHelper(OS, C, What);
284   reportBug(OS.str(), C);
285 }
286 
287 void ExprInspectionChecker::analyzerValue(const CallExpr *CE,
288                                           CheckerContext &C) const {
289   const Expr *Arg = getArgExpr(CE, C);
290   if (!Arg)
291     return;
292 
293   SVal V = C.getSVal(Arg);
294   if (const SymbolRef Sym = V.getAsSymbol())
295     printAndReport(C, Sym);
296   else if (const llvm::APSInt *I = V.getAsInteger())
297     printAndReport(C, *I);
298   else
299     reportBug("n/a", C);
300 }
301 
302 void ExprInspectionChecker::analyzerDumpSValType(const CallExpr *CE,
303                                                  CheckerContext &C) const {
304   const Expr *Arg = getArgExpr(CE, C);
305   if (!Arg)
306     return;
307 
308   QualType Ty = C.getSVal(Arg).getType(C.getASTContext());
309   reportBug(Ty.getAsString(), C);
310 }
311 
312 void ExprInspectionChecker::analyzerDump(const CallExpr *CE,
313                                          CheckerContext &C) const {
314   const Expr *Arg = getArgExpr(CE, C);
315   if (!Arg)
316     return;
317 
318   SVal V = C.getSVal(Arg);
319   printAndReport(C, V);
320 }
321 
322 void ExprInspectionChecker::analyzerGetExtent(const CallExpr *CE,
323                                               CheckerContext &C) const {
324   const Expr *Arg = getArgExpr(CE, C);
325   if (!Arg)
326     return;
327 
328   ProgramStateRef State = C.getState();
329   SVal Size = getDynamicExtentWithOffset(State, C.getSVal(Arg));
330 
331   State = State->BindExpr(CE, C.getLocationContext(), Size);
332   C.addTransition(State);
333 }
334 
335 void ExprInspectionChecker::analyzerDumpExtent(const CallExpr *CE,
336                                                CheckerContext &C) const {
337   const Expr *Arg = getArgExpr(CE, C);
338   if (!Arg)
339     return;
340 
341   ProgramStateRef State = C.getState();
342   SVal Size = getDynamicExtentWithOffset(State, C.getSVal(Arg));
343   printAndReport(C, Size);
344 }
345 
346 void ExprInspectionChecker::analyzerDumpElementCount(const CallExpr *CE,
347                                                      CheckerContext &C) const {
348   const MemRegion *MR = getArgRegion(CE, C);
349   if (!MR)
350     return;
351 
352   QualType ElementTy;
353   if (const auto *TVR = MR->getAs<TypedValueRegion>()) {
354     ElementTy = TVR->getValueType();
355   } else {
356     ElementTy = MR->castAs<SymbolicRegion>()->getPointeeStaticType();
357   }
358 
359   assert(!ElementTy->isPointerType());
360 
361   DefinedOrUnknownSVal ElementCount = getDynamicElementCountWithOffset(
362       C.getState(), C.getSVal(getArgExpr(CE, C)), ElementTy);
363   printAndReport(C, ElementCount);
364 }
365 
366 void ExprInspectionChecker::analyzerPrintState(const CallExpr *CE,
367                                                CheckerContext &C) const {
368   C.getState()->dump();
369 }
370 
371 void ExprInspectionChecker::analyzerWarnOnDeadSymbol(const CallExpr *CE,
372                                                      CheckerContext &C) const {
373   const Expr *Arg = getArgExpr(CE, C);
374   if (!Arg)
375     return;
376 
377   SVal Val = C.getSVal(Arg);
378   SymbolRef Sym = Val.getAsSymbol();
379   if (!Sym)
380     return;
381 
382   ProgramStateRef State = C.getState();
383   State = State->add<MarkedSymbols>(Sym);
384   C.addTransition(State);
385 }
386 
387 void ExprInspectionChecker::checkDeadSymbols(SymbolReaper &SymReaper,
388                                              CheckerContext &C) const {
389   ProgramStateRef State = C.getState();
390   const MarkedSymbolsTy &Syms = State->get<MarkedSymbols>();
391   ExplodedNode *N = C.getPredecessor();
392   for (SymbolRef Sym : Syms) {
393     if (!SymReaper.isDead(Sym))
394       continue;
395 
396     // The non-fatal error node should be the same for all reports.
397     if (ExplodedNode *BugNode = reportBug("SYMBOL DEAD", C))
398       N = BugNode;
399     State = State->remove<MarkedSymbols>(Sym);
400   }
401 
402   for (auto I : State->get<DenotedSymbols>()) {
403     SymbolRef Sym = I.first;
404     if (!SymReaper.isLive(Sym))
405       State = State->remove<DenotedSymbols>(Sym);
406   }
407 
408   C.addTransition(State, N);
409 }
410 
411 void ExprInspectionChecker::checkEndAnalysis(ExplodedGraph &G, BugReporter &BR,
412                                              ExprEngine &Eng) const {
413   for (auto Item : ReachedStats) {
414     unsigned NumTimesReached = Item.second.NumTimesReached;
415     ExplodedNode *N = Item.second.ExampleNode;
416 
417     reportBug(llvm::to_string(NumTimesReached), BR, N);
418   }
419   ReachedStats.clear();
420 }
421 
422 void ExprInspectionChecker::analyzerCrash(const CallExpr *CE,
423                                           CheckerContext &C) const {
424   LLVM_BUILTIN_TRAP;
425 }
426 
427 void ExprInspectionChecker::analyzerHashDump(const CallExpr *CE,
428                                              CheckerContext &C) const {
429   const LangOptions &Opts = C.getLangOpts();
430   const SourceManager &SM = C.getSourceManager();
431   FullSourceLoc FL(CE->getArg(0)->getBeginLoc(), SM);
432   std::string HashContent =
433       getIssueString(FL, getCheckerName().getName(), "Category",
434                      C.getLocationContext()->getDecl(), Opts);
435 
436   reportBug(HashContent, C);
437 }
438 
439 void ExprInspectionChecker::analyzerDenote(const CallExpr *CE,
440                                            CheckerContext &C) const {
441   if (CE->getNumArgs() < 2) {
442     reportBug("clang_analyzer_denote() requires a symbol and a string literal",
443               C);
444     return;
445   }
446 
447   SymbolRef Sym = C.getSVal(CE->getArg(0)).getAsSymbol();
448   if (!Sym) {
449     reportBug("Not a symbol", C);
450     return;
451   }
452 
453   const auto *E = dyn_cast<StringLiteral>(CE->getArg(1)->IgnoreParenCasts());
454   if (!E) {
455     reportBug("Not a string literal", C);
456     return;
457   }
458 
459   ProgramStateRef State = C.getState();
460 
461   C.addTransition(C.getState()->set<DenotedSymbols>(Sym, E));
462 }
463 
464 namespace {
465 class SymbolExpressor
466     : public SymExprVisitor<SymbolExpressor, std::optional<std::string>> {
467   ProgramStateRef State;
468 
469 public:
470   SymbolExpressor(ProgramStateRef State) : State(State) {}
471 
472   std::optional<std::string> lookup(const SymExpr *S) {
473     if (const StringLiteral *const *SLPtr = State->get<DenotedSymbols>(S)) {
474       const StringLiteral *SL = *SLPtr;
475       return std::string(SL->getBytes());
476     }
477     return std::nullopt;
478   }
479 
480   std::optional<std::string> VisitSymExpr(const SymExpr *S) {
481     return lookup(S);
482   }
483 
484   std::optional<std::string> VisitSymIntExpr(const SymIntExpr *S) {
485     if (std::optional<std::string> Str = lookup(S))
486       return Str;
487     if (std::optional<std::string> Str = Visit(S->getLHS()))
488       return (*Str + " " + BinaryOperator::getOpcodeStr(S->getOpcode()) + " " +
489               std::to_string(S->getRHS().getLimitedValue()) +
490               (S->getRHS().isUnsigned() ? "U" : ""))
491           .str();
492     return std::nullopt;
493   }
494 
495   std::optional<std::string> VisitSymSymExpr(const SymSymExpr *S) {
496     if (std::optional<std::string> Str = lookup(S))
497       return Str;
498     if (std::optional<std::string> Str1 = Visit(S->getLHS()))
499       if (std::optional<std::string> Str2 = Visit(S->getRHS()))
500         return (*Str1 + " " + BinaryOperator::getOpcodeStr(S->getOpcode()) +
501                 " " + *Str2)
502             .str();
503     return std::nullopt;
504   }
505 
506   std::optional<std::string> VisitUnarySymExpr(const UnarySymExpr *S) {
507     if (std::optional<std::string> Str = lookup(S))
508       return Str;
509     if (std::optional<std::string> Str = Visit(S->getOperand()))
510       return (UnaryOperator::getOpcodeStr(S->getOpcode()) + *Str).str();
511     return std::nullopt;
512   }
513 
514   std::optional<std::string> VisitSymbolCast(const SymbolCast *S) {
515     if (std::optional<std::string> Str = lookup(S))
516       return Str;
517     if (std::optional<std::string> Str = Visit(S->getOperand()))
518       return (Twine("(") + S->getType().getAsString() + ")" + *Str).str();
519     return std::nullopt;
520   }
521 };
522 } // namespace
523 
524 void ExprInspectionChecker::analyzerExpress(const CallExpr *CE,
525                                             CheckerContext &C) const {
526   const Expr *Arg = getArgExpr(CE, C);
527   if (!Arg)
528     return;
529 
530   SVal ArgVal = C.getSVal(CE->getArg(0));
531   SymbolRef Sym = ArgVal.getAsSymbol();
532   if (!Sym) {
533     reportBug("Not a symbol", C, ArgVal);
534     return;
535   }
536 
537   SymbolExpressor V(C.getState());
538   auto Str = V.Visit(Sym);
539   if (!Str) {
540     reportBug("Unable to express", C, ArgVal);
541     return;
542   }
543 
544   reportBug(*Str, C, ArgVal);
545 }
546 
547 void ExprInspectionChecker::analyzerIsTainted(const CallExpr *CE,
548                                               CheckerContext &C) const {
549   if (CE->getNumArgs() != 1) {
550     reportBug("clang_analyzer_isTainted() requires exactly one argument", C);
551     return;
552   }
553   const bool IsTainted =
554       taint::isTainted(C.getState(), CE->getArg(0), C.getLocationContext());
555   reportBug(IsTainted ? "YES" : "NO", C);
556 }
557 
558 void ento::registerExprInspectionChecker(CheckerManager &Mgr) {
559   Mgr.registerChecker<ExprInspectionChecker>();
560 }
561 
562 bool ento::shouldRegisterExprInspectionChecker(const CheckerManager &mgr) {
563   return true;
564 }
565