1 // MacOSXAPIChecker.h - Checks proper use of various MacOS X APIs --*- 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 defines MacOSXAPIChecker, which is an assortment of checks on calls
11 // to various, widely used Apple APIs.
12 //
13 // FIXME: What's currently in BasicObjCFoundationChecks.cpp should be migrated
14 // to here, using the new Checker interface.
15 //
16 //===----------------------------------------------------------------------===//
17
18 #include "ClangSACheckers.h"
19 #include "clang/Basic/TargetInfo.h"
20 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
21 #include "clang/StaticAnalyzer/Core/Checker.h"
22 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
24 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
25 #include "llvm/ADT/SmallString.h"
26 #include "llvm/ADT/StringSwitch.h"
27 #include "llvm/Support/raw_ostream.h"
28
29 using namespace clang;
30 using namespace ento;
31
32 namespace {
33 class MacOSXAPIChecker : public Checker< check::PreStmt<CallExpr> > {
34 mutable std::unique_ptr<BugType> BT_dispatchOnce;
35
36 public:
37 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
38
39 void CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
40 StringRef FName) const;
41
42 typedef void (MacOSXAPIChecker::*SubChecker)(CheckerContext &,
43 const CallExpr *,
44 StringRef FName) const;
45 };
46 } //end anonymous namespace
47
48 //===----------------------------------------------------------------------===//
49 // dispatch_once and dispatch_once_f
50 //===----------------------------------------------------------------------===//
51
CheckDispatchOnce(CheckerContext & C,const CallExpr * CE,StringRef FName) const52 void MacOSXAPIChecker::CheckDispatchOnce(CheckerContext &C, const CallExpr *CE,
53 StringRef FName) const {
54 if (CE->getNumArgs() < 1)
55 return;
56
57 // Check if the first argument is stack allocated. If so, issue a warning
58 // because that's likely to be bad news.
59 ProgramStateRef state = C.getState();
60 const MemRegion *R =
61 state->getSVal(CE->getArg(0), C.getLocationContext()).getAsRegion();
62 if (!R || !isa<StackSpaceRegion>(R->getMemorySpace()))
63 return;
64
65 ExplodedNode *N = C.generateSink(state);
66 if (!N)
67 return;
68
69 if (!BT_dispatchOnce)
70 BT_dispatchOnce.reset(new BugType(this, "Improper use of 'dispatch_once'",
71 "API Misuse (Apple)"));
72
73 // Handle _dispatch_once. In some versions of the OS X SDK we have the case
74 // that dispatch_once is a macro that wraps a call to _dispatch_once.
75 // _dispatch_once is then a function which then calls the real dispatch_once.
76 // Users do not care; they just want the warning at the top-level call.
77 if (CE->getLocStart().isMacroID()) {
78 StringRef TrimmedFName = FName.ltrim("_");
79 if (TrimmedFName != FName)
80 FName = TrimmedFName;
81 }
82
83 SmallString<256> S;
84 llvm::raw_svector_ostream os(S);
85 os << "Call to '" << FName << "' uses";
86 if (const VarRegion *VR = dyn_cast<VarRegion>(R))
87 os << " the local variable '" << VR->getDecl()->getName() << '\'';
88 else
89 os << " stack allocated memory";
90 os << " for the predicate value. Using such transient memory for "
91 "the predicate is potentially dangerous.";
92 if (isa<VarRegion>(R) && isa<StackLocalsSpaceRegion>(R->getMemorySpace()))
93 os << " Perhaps you intended to declare the variable as 'static'?";
94
95 BugReport *report = new BugReport(*BT_dispatchOnce, os.str(), N);
96 report->addRange(CE->getArg(0)->getSourceRange());
97 C.emitReport(report);
98 }
99
100 //===----------------------------------------------------------------------===//
101 // Central dispatch function.
102 //===----------------------------------------------------------------------===//
103
checkPreStmt(const CallExpr * CE,CheckerContext & C) const104 void MacOSXAPIChecker::checkPreStmt(const CallExpr *CE,
105 CheckerContext &C) const {
106 StringRef Name = C.getCalleeName(CE);
107 if (Name.empty())
108 return;
109
110 SubChecker SC =
111 llvm::StringSwitch<SubChecker>(Name)
112 .Cases("dispatch_once",
113 "_dispatch_once",
114 "dispatch_once_f",
115 &MacOSXAPIChecker::CheckDispatchOnce)
116 .Default(nullptr);
117
118 if (SC)
119 (this->*SC)(C, CE, Name);
120 }
121
122 //===----------------------------------------------------------------------===//
123 // Registration.
124 //===----------------------------------------------------------------------===//
125
registerMacOSXAPIChecker(CheckerManager & mgr)126 void ento::registerMacOSXAPIChecker(CheckerManager &mgr) {
127 mgr.registerChecker<MacOSXAPIChecker>();
128 }
129