diff --git a/Make.config b/Make.config
index 506a42ef32..3a92276395 100644
--- a/Make.config
+++ b/Make.config
@@ -221,6 +221,7 @@ NUNITLITE_PATH=$(TOP)/external/NUnitLite
 OPENTK_PATH=$(TOP)/external/opentk
 MODERNHTTPCLIENT_PATH=$(TOP)/external/ModernHttpClient
 XAMARIN_MACDEV_PATH=$(TOP)/external/Xamarin.MacDev
+MACCORE_PATH=$(TOP)/../maccore
 
 MONO_PREFIX ?= /Library/Frameworks/Mono.framework/Versions/Current
 SYSTEM_MCS=$(MONO_PREFIX)/bin/mcs
@@ -271,5 +272,9 @@ PRODUCT_KEY_PATH?=$(TOP)/product.snk
 
 include $(TOP)/mk/quiet.mk
 
+ifdef ENABLE_XAMARIN
+-include $(MACCORE_PATH)/Make.config
+endif
+
 .SUFFIXES:
 MAKEFLAGS += --no-builtin-rules
diff --git a/Makefile b/Makefile
index 0204949d62..bf1e64fe77 100644
--- a/Makefile
+++ b/Makefile
@@ -177,3 +177,7 @@ fix-install-permissions:
 	sudo chown -R $(USER) /Library/Frameworks/Mono.framework/External/
 	sudo chown -R $(USER) /Library/Frameworks/Xamarin.iOS.framework
 	sudo chown -R $(USER) /Library/Frameworks/Xamarin.Mac.framework
+
+ifdef ENABLE_XAMARIN
+SUBDIRS += $(MACCORE_PATH)
+endif
diff --git a/builds/Makefile b/builds/Makefile
index 3575db6774..76fc2c6744 100644
--- a/builds/Makefile
+++ b/builds/Makefile
@@ -11,6 +11,7 @@ IPHONEOS_PREFIX=$(MONOTOUCH_PREFIX)/SDKs/MonoTouch.iphoneos.sdk/usr
 ifdef ENABLE_XAMARIN
 XAMARIN_AUTOGEN_FLAGS=--enable-extension-module=xamarin
 XAMARIN_CONFIGURE_FLAGS=--enable-extension-module=xamarin
+-include $(MACCORE_PATH)/builds/Makefile.include
 endif
 
 ifndef DISABLE_STRIP
diff --git a/external/.gitignore b/external/.gitignore
new file mode 100644
index 0000000000..166bcbc362
--- /dev/null
+++ b/external/.gitignore
@@ -0,0 +1,2 @@
+mono-extensions
+
diff --git a/mk/versions.mk b/mk/versions.mk
index d5e5092a86..97eb53e45b 100644
--- a/mk/versions.mk
+++ b/mk/versions.mk
@@ -2,7 +2,7 @@
 # usage $(call CheckSubmoduleTemplate (mono,MONO,mono))
 
 define CheckSubmoduleTemplate
-#$(eval NEEDED_$(2)_VERSION:=$(shell git ls-tree HEAD --full-tree -- external/$(1) | awk -F' ' '{printf "%s",$$3}'))
+#$(eval NEEDED_$(2)_VERSION:=$(shell git --git-dir $(abspath $($(2)_PATH)/../..)/.git --work-tree $(abspath $($(2)_PATH)/../..) ls-tree HEAD --full-tree -- external/$(1) | awk -F' ' '{printf "%s",$$3}'))
 #$(eval $(2)_VERSION:=$$$$(shell cd $($(2)_PATH) 2>/dev/null && git rev-parse HEAD 2>/dev/null))
 
 check-$(1)::
@@ -42,7 +42,7 @@ ifneq ($$(IGNORE_$(2)_VERSION),)
 	@echo "*** Not resetting $(1) because IGNORE_$(2)_VERSION is set"
 else
 	@echo "*** git submodule update --init --recursive --force -- $(TOP)/external/$(1)"
-	@git submodule update --init --recursive --force -- $(TOP)/external/$(1)
+	cd $(abspath $($(2)_PATH)/../..) && git submodule update --init --recursive --force -- ./external/$(1)
 endif
 
 print-$(1)::
@@ -68,6 +68,8 @@ $(eval $(call CheckSubmoduleTemplate,opentk,OPENTK))
 $(eval $(call CheckSubmoduleTemplate,ModernHttpClient,MODERNHTTPCLIENT))
 $(eval $(call CheckSubmoduleTemplate,Xamarin.MacDev,XAMARIN_MACDEV))
 
+include $(TOP)/mk/xamarin.mk
+
 # some hackish reset-* targets to deal with what needs to happen in various parts of the build tree when you reset a module
 
 reset-mono::
diff --git a/mk/xamarin.mk b/mk/xamarin.mk
new file mode 100644
index 0000000000..cc587b266d
--- /dev/null
+++ b/mk/xamarin.mk
@@ -0,0 +1,96 @@
+ifdef ENABLE_XAMARIN
+NEEDED_MACCORE_VERSION := 32be4a29841f17f835d37d759a461267c7079b00
+NEEDED_MACCORE_BRANCH := xamarin-macios
+
+MACCORE_DIRECTORY := maccore
+MACCORE_MODULE    := git@github.com:xamarin/maccore.git
+MACCORE_VERSION   := $(shell cd $(MACCORE_PATH) 2> /dev/null && git rev-parse HEAD 2> /dev/null)
+MACCORE_BRANCH    := $(shell cd $(MACCORE_PATH) 2> /dev/null && git symbolic-ref --short HEAD 2> /dev/null)
+MACCORE_REMOTE    := origin
+MACCORE_BRANCH_AND_REMOTE := $(NEEDED_MACCORE_BRANCH) $(MACCORE_REMOTE)/$(NEEDED_MACCORE_BRANCH)
+NEEDED_MACCORE_REMOTE := $(MACCORE_REMOTE)
+
+define CheckVersionTemplate
+check-$(1)::
+	@if test x$$(IGNORE_$(2)_VERSION) = "x"; then \
+		if test ! -d $($(2)_PATH); then \
+			if test x$$(RESET_VERSIONS) != "x"; then \
+				make reset-$(1) || exit 1; \
+			else \
+				echo "Your $(1) checkout is missing, please run 'make reset-$(1)'"; \
+				touch .check-versions-failure; \
+			fi; \
+		else \
+			if test "x$($(2)_VERSION)" != "x$(NEEDED_$(2)_VERSION)" ; then \
+				if test x$$(RESET_VERSIONS) != "x"; then \
+					make reset-$(1) || exit 1; \
+				else \
+					echo "Your $(1) version is out of date, please run 'make reset-$(1)' (found $($(2)_VERSION), expected $(NEEDED_$(2)_VERSION))"; \
+					test -z "$(BUILD_REVISION)" || $(MAKE) test-$(1); \
+					touch .check-versions-failure; \
+				fi; \
+			elif test "x$($(2)_BRANCH)" != "x$(NEEDED_$(2)_BRANCH)" ; then \
+				if test x$$(RESET_VERSIONS) != "x"; then \
+					test -z "$(BUILD_REVISION)" || $(MAKE) test-$(1); \
+					make reset-$(1) || exit 1; \
+				else \
+					echo "Your $(1) branch is out of date, please run 'make reset-$(1)' (found $($(2)_BRANCH), expected $(NEEDED_$(2)_BRANCH))"; \
+					touch .check-versions-failure; \
+				fi; \
+			else \
+				echo "$(1) is up-to-date."; \
+			fi; \
+		fi; \
+	fi
+
+test-$(1)::
+	@echo $(1)
+	@echo "   $(2)_DIRECTORY=$($(2)_DIRECTORY)"
+	@echo "   $(2)_MODULE=$($(2)_MODULE)"
+	@echo "   NEEDED_$(2)_VERSION=$(NEEDED_$(2)_VERSION)"
+	@echo "   $(2)_VERSION=$($(2)_VERSION)"
+	@echo "   $(2)_BRANCH_AND_REMOTE=$($(2)_BRANCH_AND_REMOTE)"
+	@echo "   NEEDED_$(2)_BRANCH=$(NEEDED_$(2)_BRANCH)"
+	@echo "   NEEDED_$(2)_REMOTE=$(NEEDED_$(2)_REMOTE)"
+	@echo "   $(2)_BRANCH=$($(2)_BRANCH)"
+	@echo "   $(2)_PATH=$($(2)_PATH) => $(abspath $($(2)_PATH))"
+
+reset-$(1)::
+	@if test -d $($(2)_PATH); then \
+		if ! (cd $($(2)_PATH) && git show $(NEEDED_$(2)_VERSION) >/dev/null 2>&1 && git log -1 $(NEEDED_$(2)_REMOTE) >/dev/null 2>&1) ; then \
+			echo "*** git fetch `basename $$($(2)_PATH)`" && (cd $($(2)_PATH) && git fetch); \
+		fi;  \
+	else \
+		echo "*** git clone $($(2)_MODULE) --recursive $($(2)_DIRECTORY) -b $(NEEDED_$(2)_BRANCH)"; \
+		mkdir -p `dirname $($(2)_PATH)`; \
+		(cd $(abspath $($(2)_PATH)/..) && git clone $($(2)_MODULE) --recursive $($(2)_DIRECTORY) -b $(NEEDED_$(2)_BRANCH)); \
+	fi
+	@if test x$$(IGNORE_$(2)_VERSION) = "x"; then \
+		echo "*** [$(1)] git checkout -f" $(NEEDED_$(2)_BRANCH) && (cd $($(2)_PATH) && git checkout -f $(NEEDED_$(2)_BRANCH) || git checkout -f -b $($(2)_BRANCH_AND_REMOTE)); \
+		echo "*** [$(1)] git reset --hard $(NEEDED_$(2)_VERSION)" && (cd $($(2)_PATH) && git reset --hard $(NEEDED_$(2)_VERSION)); \
+	fi
+	@echo "*** [$(1)] git submodule update --init --recursive" && (cd $($(2)_PATH) && git submodule update --init --recursive)
+
+print-$(1)::
+	@printf "*** %-16s %-45s %s (%s)\n" "$(DIRECTORY_$(2))" "$(MODULE_$(2))" "$(NEEDED_$(2)_VERSION)" "$(NEEDED_$(2)_BRANCH)"
+
+.PHONY: check-$(1) reset-$(1) print-$(1)
+
+reset-versions:: reset-$(1)
+check-versions:: check-$(1)
+print-versions:: print-$(1)
+
+DEPENDENCY_DIRECTORIES += $($(2)_PATH)
+
+endef
+
+builds/.stamp-cloned-maccore:
+	@# we need to touch the stamp first, otherwise we'll 
+	@# go into an infinite loop when we re-launch make.
+	@touch $@
+	$(Q) $(MAKE) reset-maccore || rm -f $@
+
+$(eval $(call CheckVersionTemplate,maccore,MACCORE))
+-include $(MACCORE_PATH)/mk/versions.mk
+$(MACCORE_PATH)/mk/versions.mk: | builds/.stamp-cloned-maccore
+endif
diff --git a/tests/Makefile b/tests/Makefile
new file mode 100644
index 0000000000..c934fc6de1
--- /dev/null
+++ b/tests/Makefile
@@ -0,0 +1,5 @@
+TOP=..
+include $(TOP)/Make.config
+
+%:
+	$(MAKE) -C $(MACCORE_PATH)/tests $@