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//=== MallocChecker.cpp - A malloc/free checker -------------------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines malloc/free checker, which checks for potential memory
// leaks, double free, and use-after-free problems.
//
//===----------------------------------------------------------------------===//
#include "GRExprEngineExperimentalChecks.h"
#include "clang/Analysis/PathSensitive/CheckerVisitor.h"
#include "clang/Analysis/PathSensitive/GRState.h"
#include "clang/Analysis/PathSensitive/GRStateTrait.h"
#include "clang/Analysis/PathSensitive/SymbolManager.h"
#include "llvm/ADT/ImmutableMap.h"
using namespace clang;
namespace {
struct RefState {
enum Kind { Allocated, Released, Escaped } K;
const Stmt *S;
RefState(Kind k, const Stmt *s) : K(k), S(s) {}
bool isAllocated() const { return K == Allocated; }
bool isReleased() const { return K == Released; }
bool isEscaped() const { return K == Escaped; }
bool operator==(const RefState &X) const {
return K == X.K && S == X.S;
}
static RefState getAllocated(const Stmt *s) { return RefState(Allocated, s); }
static RefState getReleased(const Stmt *s) { return RefState(Released, s); }
static RefState getEscaped(const Stmt *s) { return RefState(Escaped, s); }
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(K);
ID.AddPointer(S);
}
};
class RegionState {};
class MallocChecker : public CheckerVisitor<MallocChecker> {
BuiltinBug *BT_DoubleFree;
BuiltinBug *BT_Leak;
IdentifierInfo *II_malloc;
IdentifierInfo *II_free;
public:
MallocChecker() : BT_DoubleFree(0), BT_Leak(0), II_malloc(0), II_free(0) {}
static void *getTag();
void PostVisitCallExpr(CheckerContext &C, const CallExpr *CE);
void EvalDeadSymbols(CheckerContext &C,const Stmt *S,SymbolReaper &SymReaper);
void EvalEndPath(GREndPathNodeBuilder &B, void *tag, GRExprEngine &Eng);
void PreVisitReturnStmt(CheckerContext &C, const ReturnStmt *S);
private:
void MallocMem(CheckerContext &C, const CallExpr *CE);
void FreeMem(CheckerContext &C, const CallExpr *CE);
};
} // end anonymous namespace
namespace clang {
template <>
struct GRStateTrait<RegionState>
: public GRStatePartialTrait<llvm::ImmutableMap<SymbolRef, RefState> > {
static void *GDMIndex() { return MallocChecker::getTag(); }
};
}
void clang::RegisterMallocChecker(GRExprEngine &Eng) {
Eng.registerCheck(new MallocChecker());
}
void *MallocChecker::getTag() {
static int x;
return &x;
}
void MallocChecker::PostVisitCallExpr(CheckerContext &C, const CallExpr *CE) {
const FunctionDecl *FD = CE->getDirectCallee();
if (!FD)
return;
ASTContext &Ctx = C.getASTContext();
if (!II_malloc)
II_malloc = &Ctx.Idents.get("malloc");
if (!II_free)
II_free = &Ctx.Idents.get("free");
if (FD->getIdentifier() == II_malloc) {
MallocMem(C, CE);
return;
}
if (FD->getIdentifier() == II_free) {
FreeMem(C, CE);
return;
}
}
void MallocChecker::MallocMem(CheckerContext &C, const CallExpr *CE) {
const GRState *state = C.getState();
SVal CallVal = state->getSVal(CE);
SymbolRef Sym = CallVal.getAsLocSymbol();
assert(Sym);
// Set the symbol's state to Allocated.
C.addTransition(state->set<RegionState>(Sym, RefState::getAllocated(CE)));
}
void MallocChecker::FreeMem(CheckerContext &C, const CallExpr *CE) {
const GRState *state = C.getState();
SVal ArgVal = state->getSVal(CE->getArg(0));
SymbolRef Sym = ArgVal.getAsLocSymbol();
assert(Sym);
const RefState *RS = state->get<RegionState>(Sym);
assert(RS);
// Check double free.
if (RS->isReleased()) {
ExplodedNode *N = C.GenerateSink();
if (N) {
if (!BT_DoubleFree)
BT_DoubleFree = new BuiltinBug("Double free",
"Try to free a memory block that has been released");
// FIXME: should find where it's freed last time.
BugReport *R = new BugReport(*BT_DoubleFree,
BT_DoubleFree->getDescription(), N);
C.EmitReport(R);
}
return;
}
// Normal free.
const GRState *FreedState
= state->set<RegionState>(Sym, RefState::getReleased(CE));
C.addTransition(FreedState);
}
void MallocChecker::EvalDeadSymbols(CheckerContext &C, const Stmt *S,
SymbolReaper &SymReaper) {
for (SymbolReaper::dead_iterator I = SymReaper.dead_begin(),
E = SymReaper.dead_end(); I != E; ++I) {
SymbolRef Sym = *I;
const GRState *state = C.getState();
const RefState *RS = state->get<RegionState>(Sym);
if (!RS)
return;
if (RS->isAllocated()) {
ExplodedNode *N = C.GenerateSink();
if (N) {
if (!BT_Leak)
BT_Leak = new BuiltinBug("Memory leak",
"Allocated memory never released. Potential memory leak.");
// FIXME: where it is allocated.
BugReport *R = new BugReport(*BT_Leak, BT_Leak->getDescription(), N);
C.EmitReport(R);
}
}
}
}
void MallocChecker::EvalEndPath(GREndPathNodeBuilder &B, void *tag,
GRExprEngine &Eng) {
SaveAndRestore<bool> OldHasGen(B.HasGeneratedNode);
const GRState *state = B.getState();
typedef llvm::ImmutableMap<SymbolRef, RefState> SymMap;
SymMap M = state->get<RegionState>();
for (SymMap::iterator I = M.begin(), E = M.end(); I != E; ++I) {
RefState RS = I->second;
if (RS.isAllocated()) {
ExplodedNode *N = B.generateNode(state, tag, B.getPredecessor());
if (N) {
if (!BT_Leak)
BT_Leak = new BuiltinBug("Memory leak",
"Allocated memory never released. Potential memory leak.");
BugReport *R = new BugReport(*BT_Leak, BT_Leak->getDescription(), N);
Eng.getBugReporter().EmitReport(R);
}
}
}
}
void MallocChecker::PreVisitReturnStmt(CheckerContext &C, const ReturnStmt *S) {
const Expr *RetE = S->getRetValue();
if (!RetE)
return;
const GRState *state = C.getState();
SymbolRef Sym = state->getSVal(RetE).getAsSymbol();
if (!Sym)
return;
const RefState *RS = state->get<RegionState>(Sym);
if (!RS)
return;
// FIXME: check other cases.
if (RS->isAllocated())
state = state->set<RegionState>(Sym, RefState::getEscaped(S));
C.addTransition(state);
}
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