[asan] Prevent __attribute__((annotate)) triggering errors on Darwin

[zaks.anna]

Summary

The following code triggers a fatal error in the compiler instrumentation
of ASan on Darwin because we place the attribute into llvm.metadata section,
which does not have the proper MachO section name.

void foo() __attribute__((annotate("custom")));
void foo() {;}

This commit reorders the checks so that we skip everything in llvm.metadata
first. It also removes the hard failure in case the section name does not
parse. That check will be done lower in the compilation pipeline anyway.

[kubamracek]

Good catch. This looks like a regression caused by my commit in r223513 (http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20141201/247689.html).

I'm ok with the patch, but Alexey or Alexander should see it as well.

[samsonov]

LGTM

[zaks.anna]

Committed in r239379.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
   //   - Need to poison all copies, not just the main thread's one.
   if (G->isThreadLocal()) return false;
   // For now, just ignore this Global if the alignment is large.
   if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
 
   if (G->hasSection()) {
     StringRef Section(G->getSection());
 
+    // Globals from llvm.metadata aren't emitted, do not instrument them.
+    if (Section == "llvm.metadata") return false;
+
+    // Callbacks put into the CRT initializer/terminator sections
+    // should not be instrumented.
+    // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
+    // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
+    if (Section.startswith(".CRT")) {
+      DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
+      return false;
+    }
+
     if (TargetTriple.isOSBinFormatMachO()) {
       StringRef ParsedSegment, ParsedSection;
       unsigned TAA = 0, StubSize = 0;
       bool TAAParsed;
       std::string ErrorCode = MCSectionMachO::ParseSectionSpecifier(
           Section, ParsedSegment, ParsedSection, TAA, TAAParsed, StubSize);
       if (!ErrorCode.empty()) {
-        report_fatal_error("Invalid section specifier '" + ParsedSection +
-                           "': " + ErrorCode + ".");
+        assert(false && "Invalid section specifier.");
+        return false;
       }
 
       // Ignore the globals from the __OBJC section. The ObjC runtime assumes
       // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
       // them.
       if (ParsedSegment == "__OBJC" ||
           (ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) {
         DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
if (TargetTriple.isOSBinFormatMachO()) {
       }
       // The linker merges the contents of cstring_literals and removes the
       // trailing zeroes.
       if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) {
         DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
         return false;
       }
     }
-
-    // Callbacks put into the CRT initializer/terminator sections
-    // should not be instrumented.
-    // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
-    // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
-    if (Section.startswith(".CRT")) {
-      DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
-      return false;
-    }
-
-    // Globals from llvm.metadata aren't emitted, do not instrument them.
-    if (Section == "llvm.metadata") return false;
   }
 
   return true;
 }
 
 void AddressSanitizerModule::initializeCallbacks(Module &M) {
   IRBuilder<> IRB(*C);
   // Declare our poisoning and unpoisoning functions.

test/Instrumentation/AddressSanitizer/do-not-instrument-llvm-metadata-darwin.ll

+; This test checks that we are not instrumenting globals in llvm.metadata.
+; 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-apple-macosx10.10.0"
+
+@.str_noinst = private unnamed_addr constant [4 x i8] c"aaa\00", section "llvm.metadata"
+@.str_inst = private unnamed_addr constant [4 x i8] c"aaa\00"
+
+; CHECK-NOT: {{asan_gen.*str_noinst}}
+; CHECK: {{asan_gen.*str_inst}}
+; CHECK: @asan.module_ctor