+// 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;
+
+ // Skip static allocas at the top of the entry block so they don't become
+ // dynamic when we split the block. If we used our optimized stack layout,
+ // then there will only be one alloca and it will come first.
+ BasicBlock &Entry = F.getEntryBlock();
+ BasicBlock::iterator IP = Entry.getFirstInsertionPt(), BE = Entry.end();
+ for (; IP != BE; ++IP) {
+ AllocaInst *AI = dyn_cast<AllocaInst>(IP);
+ if (!AI || !AI->isStaticAlloca())
+ break;
+ }
+
+ IRBuilder<> IRB(IP);
+ Type *Int8Ty = IRB.getInt8Ty();
+ GlobalVariable *Guard = new GlobalVariable(
+ *F.getParent(), Int8Ty, false, GlobalValue::PrivateLinkage,
+ 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(Cmp, IP, 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;
+}
+