Fix ASan issue 305 -- don't instrument .CRT initializer/terminator callbacks

[timurrrr]

Summary

See http://code.google.com/p/address-sanitizer/issues/detail?id=305 for more details

[glider]

LGTM.
Please add a link to the CRT documentation (e.g. http://msdn.microsoft.com/ru-ru/library/bb918180(v=vs.100).aspx) and make sure there's a test.

[timurrrr]

r207968.

I've added the link to MSDN and (as discussed offline) relaxed the name check a little bit.

Will commit a test separately.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

if ((G->getName().find("\01L_OBJC_") == 0) ||
     return false;
   }
 
   if (G->hasSection()) {
     StringRef Section(G->getSection());
     // 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 ((Section.find("__OBJC,") == 0) ||
-        (Section.find("__DATA, __objc_") == 0)) {
+    if (Section.startswith("__OBJC,") ||
+        Section.startswith("__DATA, __objc_")) {
       DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
       return false;
     }
     // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
     // Constant CFString instances are compiled in the following way:
     //  -- the string buffer is emitted into
     //     __TEXT,__cstring,cstring_literals
     //  -- the constant NSConstantString structure referencing that buffer
     //     is placed into __DATA,__cfstring
     // Therefore there's no point in placing redzones into __DATA,__cfstring.
     // Moreover, it causes the linker to crash on OS X 10.7
-    if (Section.find("__DATA,__cfstring") == 0) {
+    if (Section.startswith("__DATA,__cfstring")) {
       DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n");
       return false;
     }
     // The linker merges the contents of cstring_literals and removes the
     // trailing zeroes.
-    if (Section.find("__TEXT,__cstring,cstring_literals") == 0) {
+    if (Section.startswith("__TEXT,__cstring,cstring_literals")) {
       DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
       return false;
     }
+
+    // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
+    // Callbacks put into the CRT initializer/terminator sections
+    // should not be instrumented.
+    if (Section.startswith(".CRT") && Section.find("$") != StringRef::npos) {
+      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) {