[compiler-rt] Avoid instrumenting sanitizer functions

Summary:
Function __asan_default_options is called by __asan_init before the
shadow memory got initialized. Instrumenting that function may lead
to flaky execution.

As the __asan_default_options is provided by users, we cannot expect
them to add the appropriate function atttributes to avoid
instrumentation.

Reviewers: kcc, rnk

Subscribers: dberris, chrisha, llvm-commits

Differential Revision: https://reviews.llvm.org/D24566

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281503 91177308-0d34-0410-b5e6-96231b3b80d8

Author: bergeret

lib/Transforms/Instrumentation/AddressSanitizer.cpp

@@ -1882,17 +1882,21 @@ void AddressSanitizer::markEscapedLocalAllocas(Function &F) {
 bool AddressSanitizer::runOnFunction(Function &F) {
   if (&F == AsanCtorFunction) return false;
   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
-  DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
-  initializeCallbacks(*F.getParent());
-
-  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+  if (!ClDebugFunc.empty() && ClDebugFunc == F.getName()) return false;
+  if (F.getName().find("__asan_") != std::string::npos) return false;
 
   // If needed, insert __asan_init before checking for SanitizeAddress attr.
+  // This function needs to be called even if the function body is not
+  // instrumented.  
   maybeInsertAsanInitAtFunctionEntry(F);
-
+  
+  // Leave if the function doesn't need instrumentation.
   if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return false;
 
-  if (!ClDebugFunc.empty() && ClDebugFunc != F.getName()) return false;
+  DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
+
+  initializeCallbacks(*F.getParent());
+  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
 
   FunctionStateRAII CleanupObj(this);
 

test/Instrumentation/AddressSanitizer/do-not-instrument-sanitizers.ll

@@ -0,0 +1,24 @@
+; This test checks that we are not instrumenting sanitizer code.
+; RUN: opt < %s -asan -asan-module -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; Function Attrs: nounwind uwtable
+define void @__asan_default_options(i32* %a) sanitize_address {
+entry:
+  %tmp1 = load i32, i32* %a, align 4
+  %tmp2 = add i32 %tmp1,  1
+  store i32 %tmp2, i32* %a, align 4
+  ret void
+}
+
+; CHECK-NOT: call void @__asan_report_load
+
+; Function Attrs: nounwind uwtable
+define i32 @main() #0 {
+entry:
+  ret i32 0
+}
+
+; CHECK: declare void @__asan_init()