[sanitizer] Add early call handling to strlen interceptor

[bruening]

Summary

The strlen interceptor is sometimes invoked too early for REAL(strlen) to
be initialized. A special check is added to use internal_strlen for this
situation.

[bruening]

I wonder if you could confirm that this fixes the failure you were seeing on FreeBSD?

[dim]

Yes, this fixes all the ASan tests which were broken on FreeBSD after rL263177. Tested on i386-freebsd11, amd64-freebsd11 (and even x86_64-darwin15 :) ) Thanks!

[dim]

@bruening, do you have commit access? Otherwise I'll commit it.

[bruening]

Yes, I committed it as r265705. Strange, it lists this page in the commit (http://reviews.llvm.org/rL265705), yet it didn't auto-close here -- did I not commit it in the right way?

[dim]

The commit message looks just fine to me, it includes the correct Differential Revision: header, as far as I can see. Let's just call it a fluke and close this review. :)

[emaste]

In D18851#395994, @bruening wrote:

Yes, I committed it as r265705. Strange, it lists this page in the commit (http://reviews.llvm.org/rL265705), yet it didn't auto-close here -- did I not commit it in the right way?

Phabricator only detects Differential Revision: at the end of the commit message. The Change-Id text after it in rL265705 is the reason it didn't auto-close.

lib/sanitizer_common/sanitizer_common_interceptors.inc

 UNUSED static void DeleteInterceptorMetadata(void *addr) {
   MetadataHashMap::Handle h(interceptor_metadata_map, (uptr)addr, true);
   CHECK(h.exists());
 }
 #endif  // SI_NOT_WINDOWS
 
 #if SANITIZER_INTERCEPT_STRLEN
 INTERCEPTOR(SIZE_T, strlen, const char *s) {
+  // Sometimes strlen is called prior to InitializeCommonInterceptors,
+  // in which case the REAL(strlen) typically used in
+  // COMMON_INTERCEPTOR_ENTER will fail.  We use internal_strlen here
+  // to handle that.
+  if (COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED)
+    return internal_strlen(s);
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, strlen, s);
   SIZE_T result = REAL(strlen)(s);
   if (common_flags()->intercept_strlen)
     COMMON_INTERCEPTOR_READ_RANGE(ctx, s, result + 1);
   return result;
 }
 #define INIT_STRLEN COMMON_INTERCEPT_FUNCTION(strlen)