[compiler-rt] Avoid instrumenting sanitizer functions

[etienneb]

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.

[rnk]

lgtm

[kcc]

lib/Transforms/Instrumentation/AddressSanitizer.cpp

1886

please use startswith() instead of find()

[etienneb]

addressed kcc comment's in revision:

Committed revision 281617.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

if (II && II->getIntrinsicID() == Intrinsic::localescape) {
       break;
     }
   }
 }
 
 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);
 
   // We can't instrument allocas used with llvm.localescape. Only static allocas
   // can be passed to that intrinsic.
   markEscapedLocalAllocas(F);
 
   // We want to instrument every address only once per basic block (unless there

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

+; 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()
 No newline at end of file