Move the glibc unlimited stack hack into GetThreadStack.

Optional cleanup that was previously a TODO.

Bug: 17111575
Change-Id: I7c20dbf1fdbcaf4604d7b55552930c10e166539d
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 7d69828..e0d67d6 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -507,40 +507,9 @@
     + 4 * KB;
   if (read_stack_size <= min_stack) {
     LOG(FATAL) << "Attempt to attach a thread with a too-small stack (" << read_stack_size
-        << " bytes)";
+               << " bytes)";
   }
 
-  // TODO: move this into the Linux GetThreadStack implementation.
-#if !defined(__APPLE__)
-  // If we're the main thread, check whether we were run with an unlimited stack. In that case,
-  // glibc will have reported a 2GB stack for our 32-bit process, and our stack overflow detection
-  // will be broken because we'll die long before we get close to 2GB.
-  bool is_main_thread = (::art::GetTid() == getpid());
-  if (is_main_thread) {
-    rlimit stack_limit;
-    if (getrlimit(RLIMIT_STACK, &stack_limit) == -1) {
-      PLOG(FATAL) << "getrlimit(RLIMIT_STACK) failed";
-    }
-    if (stack_limit.rlim_cur == RLIM_INFINITY) {
-      // Find the default stack size for new threads...
-      pthread_attr_t default_attributes;
-      size_t default_stack_size;
-      CHECK_PTHREAD_CALL(pthread_attr_init, (&default_attributes), "default stack size query");
-      CHECK_PTHREAD_CALL(pthread_attr_getstacksize, (&default_attributes, &default_stack_size),
-                         "default stack size query");
-      CHECK_PTHREAD_CALL(pthread_attr_destroy, (&default_attributes), "default stack size query");
-
-      // ...and use that as our limit.
-      size_t old_stack_size = read_stack_size;
-      tlsPtr_.stack_size = default_stack_size;
-      tlsPtr_.stack_begin += (old_stack_size - default_stack_size);
-      VLOG(threads) << "Limiting unlimited stack (reported as " << PrettySize(old_stack_size) << ")"
-                    << " to " << PrettySize(default_stack_size)
-                    << " with base " << reinterpret_cast<void*>(tlsPtr_.stack_begin);
-    }
-  }
-#endif
-
   // Set stack_end_ to the bottom of the stack saving space of stack overflows
 
   Runtime* runtime = Runtime::Current();
diff --git a/runtime/utils.cc b/runtime/utils.cc
index 55ecc1e..680cb44 100644
--- a/runtime/utils.cc
+++ b/runtime/utils.cc
@@ -108,6 +108,31 @@
   CHECK_PTHREAD_CALL(pthread_attr_getstack, (&attributes, stack_base, stack_size), __FUNCTION__);
   CHECK_PTHREAD_CALL(pthread_attr_getguardsize, (&attributes, guard_size), __FUNCTION__);
   CHECK_PTHREAD_CALL(pthread_attr_destroy, (&attributes), __FUNCTION__);
+
+#if defined(__GLIBC__)
+  // If we're the main thread, check whether we were run with an unlimited stack. In that case,
+  // glibc will have reported a 2GB stack for our 32-bit process, and our stack overflow detection
+  // will be broken because we'll die long before we get close to 2GB.
+  bool is_main_thread = (::art::GetTid() == getpid());
+  if (is_main_thread) {
+    rlimit stack_limit;
+    if (getrlimit(RLIMIT_STACK, &stack_limit) == -1) {
+      PLOG(FATAL) << "getrlimit(RLIMIT_STACK) failed";
+    }
+    if (stack_limit.rlim_cur == RLIM_INFINITY) {
+      size_t old_stack_size = *stack_size;
+
+      // Use the kernel default limit as our size, and adjust the base to match.
+      *stack_size = 8 * MB;
+      *stack_base = reinterpret_cast<uint8_t*>(*stack_base) + (old_stack_size - *stack_size);
+
+      VLOG(threads) << "Limiting unlimited stack (reported as " << PrettySize(old_stack_size) << ")"
+                    << " to " << PrettySize(*stack_size)
+                    << " with base " << *stack_base;
+    }
+  }
+#endif
+
 #endif
 }