[asancov] Emit an initializer passing number of coverage code locations in each module

[eugenis]

Summary

This is required for D3874.

[eugenis]

Instrumentation-side changes in D3898.
PTAL.

[kcc]

LGTM

[Eugene.Zelenko]

Committed in rL209654.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

 static const char *const kAsanReportLoadN = "__asan_report_load_n";
 static const char *const kAsanReportStoreN = "__asan_report_store_n";
 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
 static const char *const kAsanUnregisterGlobalsName =
     "__asan_unregister_globals";
 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 kAsanCovModuleInitName = "__sanitizer_cov_module_init";
 static const char *const kAsanCovName = "__sanitizer_cov";
 static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
 static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
 static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
 static const int         kMaxAsanStackMallocSizeClass = 10;
 static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
 static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
 static const char *const kAsanGenPrefix = "__asan_gen_";
private:
   Type *IntptrTy;
   LLVMContext *C;
   const DataLayout *DL;
   ShadowMapping Mapping;
   Function *AsanPoisonGlobals;
   Function *AsanUnpoisonGlobals;
   Function *AsanRegisterGlobals;
   Function *AsanUnregisterGlobals;
+  Function *AsanCovModuleInit;
 };
 
 // Stack poisoning does not play well with exception handling.
 // When an exception is thrown, we essentially bypass the code
 // that unpoisones the stack. This is why the run-time library has
 // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
 // stack in the interceptor. This however does not work inside the
 // actual function which catches the exception. Most likely because the
void AddressSanitizerModule::initializeCallbacks(Module &M) {
   AsanRegisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
       kAsanRegisterGlobalsName, IRB.getVoidTy(),
       IntptrTy, IntptrTy, NULL));
   AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
   AsanUnregisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
       kAsanUnregisterGlobalsName,
       IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
   AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
+  AsanCovModuleInit = checkInterfaceFunction(M.getOrInsertFunction(
+      kAsanCovModuleInitName,
+      IRB.getVoidTy(), IntptrTy, NULL));
+  AsanCovModuleInit->setLinkage(Function::ExternalLinkage);
 }
 
 // This function replaces all global variables with new variables that have
 // trailing redzones. It also creates a function that poisons
 // redzones and inserts this function into llvm.global_ctors.
 bool AddressSanitizerModule::runOnModule(Module &M) {
   if (!ClGlobals) return false;
 
bool AddressSanitizerModule::runOnModule(Module &M) {
   SmallVector<GlobalVariable *, 16> GlobalsToChange;
 
   for (Module::GlobalListType::iterator G = M.global_begin(),
        E = M.global_end(); G != E; ++G) {
     if (ShouldInstrumentGlobal(G))
       GlobalsToChange.push_back(G);
   }
 
+  Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
+  assert(CtorFunc);
+  IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
+
+  Function *CovFunc = M.getFunction(kAsanCovName);
+  int nCov = CovFunc ? CovFunc->getNumUses() : 0;
+  IRB.CreateCall(AsanCovModuleInit, ConstantInt::get(IntptrTy, nCov));
+
   size_t n = GlobalsToChange.size();
   if (n == 0) return false;
 
   // A global is described by a structure
   //   size_t beg;
   //   size_t size;
   //   size_t size_with_redzone;
   //   const char *name;
   //   const char *module_name;
   //   size_t has_dynamic_init;
   // We initialize an array of such structures and pass it to a run-time call.
   StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
                                                IntptrTy, IntptrTy,
                                                IntptrTy, IntptrTy, NULL);
   SmallVector<Constant *, 16> Initializers(n);
 
-  Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
-  assert(CtorFunc);
-  IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
-
   bool HasDynamicallyInitializedGlobals = false;
 
   // We shouldn't merge same module names, as this string serves as unique
   // module ID in runtime.
   GlobalVariable *ModuleName = createPrivateGlobalForString(
       M, M.getModuleIdentifier(), /*AllowMerging*/false);
 
   for (size_t i = 0; i < n; i++) {

test/Instrumentation/AddressSanitizer/coverage.ll

entry:
 
   if.then:                                          ; preds = %entry
   store i32 0, i32* %a, align 4
   br label %if.end
 
   if.end:                                           ; preds = %entry, %if.then
   ret void
 }
+
 ; CHECK1-LABEL: define void @foo
 ; CHECK1: %0 = load atomic i8* @__asan_gen_cov_foo monotonic, align 1
 ; CHECK1: %1 = icmp eq i8 0, %0
 ; CHECK1: br i1 %1, label %2, label %3
 ; CHECK1: call void @__sanitizer_cov
 ; CHECK1-NOT: call void @__sanitizer_cov
 ; CHECK1: store atomic i8 1, i8* @__asan_gen_cov_foo monotonic, align 1
 
+; CHECK1-LABEL: define internal void @asan.module_ctor
+; CHECK1-NOT: ret
+; CHECK1: call void @__sanitizer_cov_module_init(i64 1)
+; CHECK1: ret
+
+
 ; CHECK2-LABEL: define void @foo
 ; CHECK2: call void @__sanitizer_cov
 ; CHECK2: call void @__sanitizer_cov
 ; CHECK2: call void @__sanitizer_cov
 ; CHECK2-NOT: call void @__sanitizer_cov
 ; CHECK2: ret void
+
+; CHECK2-LABEL: define internal void @asan.module_ctor
+; CHECK2-NOT: ret
+; CHECK2: call void @__sanitizer_cov_module_init(i64 3)
+; CHECK2: ret