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//= UnixAPIChecker.h - Checks preconditions for various Unix APIs --*- C++ -*-//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This defines UnixAPIChecker, which is an assortment of checks on calls
// to various, widely used UNIX/Posix functions.
//
//===----------------------------------------------------------------------===//
#include "GRExprEngineInternalChecks.h"
#include "clang/Checker/PathSensitive/CheckerVisitor.h"
#include "clang/Checker/BugReporter/BugType.h"
#include "llvm/ADT/StringSwitch.h"
#include <fcntl.h>
using namespace clang;
namespace {
class UnixAPIChecker : public CheckerVisitor<UnixAPIChecker> {
enum SubChecks {
OpenFn = 0,
NumChecks
};
BugType *BTypes[NumChecks];
public:
UnixAPIChecker() { memset(BTypes, 0, sizeof(*BTypes) * NumChecks); }
static void *getTag() { static unsigned tag = 0; return &tag; }
void PreVisitCallExpr(CheckerContext &C, const CallExpr *CE);
};
} //end anonymous namespace
void clang::RegisterUnixAPIChecker(GRExprEngine &Eng) {
Eng.registerCheck(new UnixAPIChecker());
}
//===----------------------------------------------------------------------===//
// Utility functions.
//===----------------------------------------------------------------------===//
static inline void LazyInitialize(BugType *&BT, const char *name) {
if (BT)
return;
BT = new BugType(name, "Unix API");
}
//===----------------------------------------------------------------------===//
// "open" (man 2 open)
//===----------------------------------------------------------------------===//
static void CheckOpen(CheckerContext &C, const CallExpr *CE, BugType *&BT) {
LazyInitialize(BT, "Improper use of 'open'");
// Look at the 'oflags' argument for the O_CREAT flag.
const GRState *state = C.getState();
if (CE->getNumArgs() < 2) {
// The frontend should issue a warning for this case, so this is a sanity
// check.
return;
}
// Now check if oflags has O_CREAT set.
const Expr *oflagsEx = CE->getArg(1);
const SVal V = state->getSVal(oflagsEx);
if (!isa<NonLoc>(V)) {
// The case where 'V' can be a location can only be due to a bad header,
// so in this case bail out.
return;
}
NonLoc oflags = cast<NonLoc>(V);
NonLoc ocreateFlag =
cast<NonLoc>(C.getValueManager().makeIntVal((uint64_t) O_CREAT,
oflagsEx->getType()));
SVal maskedFlagsUC = C.getSValuator().EvalBinOpNN(state, BinaryOperator::And,
oflags, ocreateFlag,
oflagsEx->getType());
if (maskedFlagsUC.isUnknownOrUndef())
return;
DefinedSVal maskedFlags = cast<DefinedSVal>(maskedFlagsUC);
// Check if maskedFlags is non-zero.
const GRState *trueState, *falseState;
llvm::tie(trueState, falseState) = state->Assume(maskedFlags);
// Only emit an error if the value of 'maskedFlags' is properly
// constrained;
if (!(trueState && !falseState))
return;
if (CE->getNumArgs() < 3) {
ExplodedNode *N = C.GenerateSink(trueState);
if (!N)
return;
EnhancedBugReport *report =
new EnhancedBugReport(*BT,
"Call to 'open' requires a third argument when "
"the 'O_CREAT' flag is set", N);
report->addRange(oflagsEx->getSourceRange());
C.EmitReport(report);
}
}
//===----------------------------------------------------------------------===//
// Central dispatch function.
//===----------------------------------------------------------------------===//
typedef void (*SubChecker)(CheckerContext &C, const CallExpr *CE, BugType *&BT);
namespace {
class SubCheck {
SubChecker SC;
BugType **BT;
public:
SubCheck(SubChecker sc, BugType *& bt) : SC(sc), BT(&bt) {}
SubCheck() : SC(NULL), BT(NULL) {}
void run(CheckerContext &C, const CallExpr *CE) const {
if (SC)
SC(C, CE, *BT);
}
};
} // end anonymous namespace
void UnixAPIChecker::PreVisitCallExpr(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 FunctionTextRegion *Fn =
dyn_cast_or_null<FunctionTextRegion>(state->getSVal(Callee).getAsRegion());
if (!Fn)
return;
const IdentifierInfo *FI = Fn->getDecl()->getIdentifier();
if (!FI)
return;
const SubCheck &SC =
llvm::StringSwitch<SubCheck>(FI->getName())
.Case("open", SubCheck(CheckOpen, BTypes[OpenFn]))
.Default(SubCheck());
SC.run(C, CE);
}
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