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[asan] Poor man's coverage that works with ASan

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194701 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kostya Serebryany
2013-11-14 13:27:41 +00:00
parent 45f5110634
commit 8cc5f7cd59
2 changed files with 65 additions and 0 deletions
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52
lib/Transforms/Instrumentation/AddressSanitizer.cpp
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@@ -77,6 +77,7 @@ static const char *const kAsanUnregisterGlobalsName =
static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
static const char *const kAsanInitName = "__asan_init_v3";
static const char *const kAsanCovName = "__sanitizer_cov";
static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
static const char *const kAsanMappingOffsetName = "__asan_mapping_offset";
static const char *const kAsanMappingScaleName = "__asan_mapping_scale";
@@ -134,6 +135,8 @@ static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
// This flag may need to be replaced with -f[no]asan-globals.
static cl::opt<bool> ClGlobals("asan-globals",
cl::desc("Handle global objects"), cl::Hidden, cl::init(true));
static cl::opt<bool> ClCoverage("asan-coverage",
cl::desc("ASan coverage"), cl::Hidden, cl::init(false));
static cl::opt<bool> ClInitializers("asan-initialization-order",
cl::desc("Handle C++ initializer order"), cl::Hidden, cl::init(false));
static cl::opt<bool> ClMemIntrin("asan-memintrin",
@@ -324,6 +327,7 @@ struct AddressSanitizer : public FunctionPass {
bool LooksLikeCodeInBug11395(Instruction *I);
void FindDynamicInitializers(Module &M);
bool GlobalIsLinkerInitialized(GlobalVariable *G);
bool InjectCoverage(Function &F);
bool CheckInitOrder;
bool CheckUseAfterReturn;
@@ -339,6 +343,7 @@ struct AddressSanitizer : public FunctionPass {
Function *AsanCtorFunction;
Function *AsanInitFunction;
Function *AsanHandleNoReturnFunc;
Function *AsanCovFunction;
OwningPtr<SpecialCaseList> BL;
// This array is indexed by AccessIsWrite and log2(AccessSize).
Function *AsanErrorCallback[2][kNumberOfAccessSizes];
@@ -1085,6 +1090,8 @@ void AddressSanitizer::initializeCallbacks(Module &M) {
AsanHandleNoReturnFunc = checkInterfaceFunction(M.getOrInsertFunction(
kAsanHandleNoReturnName, IRB.getVoidTy(), NULL));
AsanCovFunction = checkInterfaceFunction(M.getOrInsertFunction(
kAsanCovName, IRB.getVoidTy(), IntptrTy, NULL));
// We insert an empty inline asm after __asan_report* to avoid callback merge.
EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
StringRef(""), StringRef(""),
@@ -1156,6 +1163,47 @@ bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
return false;
}
// Poor man's coverage that works with ASan.
// We create a Guard boolean variable with the same linkage
// as the function and inject this code into the entry block:
// if (*Guard) {
// __sanitizer_cov(&F);
// *Guard = 1;
// }
// The accesses to Guard are atomic. The rest of the logic is
// in __sanitizer_cov (it's fine to call it more than once).
//
// This coverage implementation provides very limited data:
// it only tells if a given function was ever executed.
// No counters, no per-basic-block or per-edge data.
// But for many use cases this is what we need and the added slowdown
// is negligible. This simple implementation will probably be obsoleted
// by the upcoming Clang-based coverage implementation.
// By having it here and now we hope to
// a) get the functionality to users earlier and
// b) collect usage statistics to help improve Clang coverage design.
bool AddressSanitizer::InjectCoverage(Function &F) {
if (!ClCoverage) return false;
IRBuilder<> IRB(F.getEntryBlock().getFirstInsertionPt());
Type *Int8Ty = IRB.getInt8Ty();
GlobalVariable *Guard = new GlobalVariable(
*F.getParent(), Int8Ty, false, F.getLinkage(),
Constant::getNullValue(Int8Ty), "__asan_gen_cov_" + F.getName());
LoadInst *Load = IRB.CreateLoad(Guard);
Load->setAtomic(Monotonic);
Load->setAlignment(1);
Value *Cmp = IRB.CreateICmpEQ(Constant::getNullValue(Int8Ty), Load);
Instruction *Ins = SplitBlockAndInsertIfThen(cast<Instruction>(Cmp), false);
IRB.SetInsertPoint(Ins);
// We pass &F to __sanitizer_cov. We could avoid this and rely on
// GET_CALLER_PC, but having the PC of the first instruction is just nice.
IRB.CreateCall(AsanCovFunction, IRB.CreatePointerCast(&F, IntptrTy));
StoreInst *Store = IRB.CreateStore(ConstantInt::get(Int8Ty, 1), Guard);
Store->setAtomic(Monotonic);
Store->setAlignment(1);
return true;
}
bool AddressSanitizer::runOnFunction(Function &F) {
if (BL->isIn(F)) return false;
if (&F == AsanCtorFunction) return false;
@@ -1251,6 +1299,10 @@ bool AddressSanitizer::runOnFunction(Function &F) {
}
bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
if (InjectCoverage(F))
res = true;
DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
if (ClKeepUninstrumented) {