diff --git a/mono/metadata/metadata-cross-helpers.c b/mono/metadata/metadata-cross-helpers.c
index 595369140103a..90a4d332bd129 100644
--- a/mono/metadata/metadata-cross-helpers.c
+++ b/mono/metadata/metadata-cross-helpers.c
@@ -1,6 +1,137 @@
+#include <stdio.h>
+
 #include "config.h"
+#include <mono/metadata/abi-details.h>
+
+#include <mono/metadata/class-internals.h>
+#include <mono/metadata/object-internals.h>
+#include <mono/metadata/monitor.h>
+#ifdef HAVE_SGEN_GC
+#include <mono/sgen/sgen-gc.h>
+#endif
+
+static int
+dump_arch (void)
+{
+#if defined (TARGET_X86)
+	g_print ("#ifdef TARGET_X86\n");
+#elif defined (TARGET_AMD64)
+	g_print ("#ifdef TARGET_AMD64\n");
+#elif defined (TARGET_ARM)
+	g_print ("#ifdef TARGET_ARM\n");
+#elif defined (TARGET_ARM64)
+	g_print ("#ifdef TARGET_ARM64\n");
+#else
+	return 0;
+#endif
+	return 1;
+}
+
+static int
+dump_os (void)
+{
+#if defined (PLATFORM_WIN32)
+	g_print ("#ifdef TARGET_WIN32\n");
+#elif defined (PLATFORM_ANDROID)
+	g_print ("#ifdef TARGET_ANDROID\n");
+#elif defined (PLATFORM_MACOSX)
+	g_print ("#ifdef TARGET_OSX\n");
+#elif defined (PLATFORM_IOS)
+	g_print ("#ifdef TARGET_IOS\n");
+#else
+	return 0;
+#endif
+	return 1;
+}
+
+void
+mono_dump_metadata_offsets (void);
+
+void
+mono_dump_metadata_offsets (void)
+{
+#ifdef USED_CROSS_COMPILER_OFFSETS
+	g_print ("not using native offsets\n");
+#else
+	g_print ("#ifndef USED_CROSS_COMPILER_OFFSETS\n");
+
+	if (!dump_arch ()) {
+		g_print ("#error failed to figure out the current arch\n");
+		return;
+	}
+
+	if (!dump_os ()) {
+		g_print ("#error failed to figure out the current OS\n");
+		return;
+	}
+
+#ifdef HAVE_SGEN_GC
+	g_print ("#ifndef HAVE_BOEHM_GC\n");
+#elif HAVE_BOEHM_GC
+	g_print ("#ifndef HAVE_SGEN_GC\n");
+#else
+	g_print ("#error no gc conf not supported\n");
+	return;
+#endif
+
+	g_print ("#define HAS_CROSS_COMPILER_OFFSETS\n");
+	g_print ("#if defined (USE_CROSS_COMPILE_OFFSETS) || defined (MONO_CROSS_COMPILE)\n");
+	g_print ("#if !defined (DISABLE_METADATA_OFFSETS)\n");
+	g_print ("#define USED_CROSS_COMPILER_OFFSETS\n");
+
+#define DISABLE_JIT_OFFSETS
+#define DECL_OFFSET2(struct,field,offset) this_should_not_happen
+#define DECL_ALIGN2(type,size) this_should_not_happen
+
+#define DECL_OFFSET(struct,field) g_print ("DECL_OFFSET2(%s,%s,%d)\n", #struct, #field, (int)MONO_STRUCT_OFFSET (struct, field));
+#define DECL_ALIGN(type) g_print ("DECL_ALIGN2(%s,%d)\n", #type, (int)MONO_ABI_ALIGNOF (type));
+#define DECL_SIZE(type) g_print ("DECL_SIZE2(%s,%d)\n", #type, (int)MONO_ABI_SIZEOF (type));
+#include <mono/metadata/object-offsets.h>
+
+	g_print ("#endif //disable metadata check\n");
+	g_print ("#endif //gc check\n");
+#endif
+}
+
+void
+mono_metadata_cross_helpers_run (void);
+
+void
+mono_metadata_cross_helpers_run (void)
+{
+#if defined (HAS_CROSS_COMPILER_OFFSETS) && !defined (MONO_CROSS_COMPILE)
+	gboolean is_broken = FALSE;
+
+#define DISABLE_JIT_OFFSETS
+#define USE_CROSS_COMPILE_OFFSETS
+#define DECL_OFFSET(struct,field) this_should_not_happen_for_cross_fields
+#define DECL_OFFSET2(struct,field,offset) \
+	 if ((int)G_STRUCT_OFFSET (struct, field) != offset) { \
+		g_print (#struct ":" #field " invalid struct offset %d (expected %d)\n",	\
+			offset,	\
+			(int)G_STRUCT_OFFSET (struct, field));	\
+		is_broken = TRUE;	\
+	}
+#define DECL_ALIGN(type) this_should_not_happen_for_cross_align
+#define DECL_ALIGN2(name,size) \
+	 if (MONO_ALIGN_ ## name != size) { \
+		g_print (#name ": invalid alignment %d (expected %d)\n",	\
+		size,	\
+		MONO_ALIGN_ ## name);	\
+		is_broken = TRUE;	\
+	}
+#define DECL_SIZE(type) this_should_not_happen_for_cross_size
+#define DECL_SIZE2(name,size) \
+	 if (MONO_SIZEOF_ ## name != size) { \
+		g_print (#name ": invalid size %d (expected %d)\n",	\
+		size,	\
+		MONO_SIZEOF_ ## name);	\
+		is_broken = TRUE;	\
+	}
+
+#include <mono/metadata/object-offsets.h>
 
-#ifdef ENABLE_EXTENSION_MODULE
-#include "../../../mono-extensions/mono/metadata/metadata-cross-helpers.c"
+	g_assert (!is_broken);
 #endif
+}
 
diff --git a/mono/mini/mini-cross-helpers.c b/mono/mini/mini-cross-helpers.c
index dede99f3ee9ab..28e04d6d62883 100644
--- a/mono/mini/mini-cross-helpers.c
+++ b/mono/mini/mini-cross-helpers.c
@@ -1,13 +1,93 @@
 #include "config.h"
 
-#ifdef ENABLE_EXTENSION_MODULE
-#include "../../../mono-extensions/mono/mini/mini-cross-helpers.c"
+#include <stdio.h>
+
+#include "config.h"
+
+#include "mini.h"
+#include "tasklets.h"
+#include <mono/metadata/abi-details.h>
+
+void
+mono_dump_metadata_offsets (void);
+
+void
+mono_metadata_cross_helpers_run (void);
+
+
+static void
+mono_dump_jit_offsets (void)
+{
+#ifdef USED_CROSS_COMPILER_OFFSETS
+	g_print ("#error not using native offsets\n");
 #else
+	mono_dump_metadata_offsets ();
+
+	g_print ("#ifndef DISABLE_JIT_OFFSETS\n");
+	g_print ("#define USED_CROSS_COMPILER_OFFSETS\n");
+#define DISABLE_METADATA_OFFSETS
+#define DECL_OFFSET2(struct,field,offset) this_should_not_happen
+#define DECL_ALIGN2(type,size) this_should_not_happen
 
-void mono_cross_helpers_run (void);
+#define DECL_OFFSET(struct,field) g_print ("DECL_OFFSET2(%s,%s,%d)\n", #struct, #field, (int)MONO_STRUCT_OFFSET (struct, field));
+#define DECL_ALIGN(type)
+#define DECL_SIZE2(type,size) this_should_not_happen
+#define DECL_SIZE(type)
+#include <mono/metadata/object-offsets.h>
+
+	g_print ("#endif //disable jit check\n");
+	g_print ("#endif //cross compiler checks\n");
+	g_print ("#endif //gc check\n");
+	g_print ("#endif //os check\n");
+	g_print ("#endif //arch check\n");
+	g_print ("#endif //USED_CROSS_COMPILER_OFFSETS check\n");
+#endif
+}
 
 void
 mono_cross_helpers_run (void)
 {
-}
+#if defined (HAS_CROSS_COMPILER_OFFSETS) && !defined (MONO_CROSS_COMPILE)
+	gboolean is_broken = FALSE;
+#endif
+
+#ifndef USED_CROSS_COMPILER_OFFSETS
+	if (g_getenv ("DUMP_CROSS_OFFSETS"))
+		mono_dump_jit_offsets ();
 #endif
+	
+#if defined (HAS_CROSS_COMPILER_OFFSETS) && !defined (MONO_CROSS_COMPILE)
+	mono_metadata_cross_helpers_run ();
+
+#define DISABLE_METADATA_OFFSETS
+#define USE_CROSS_COMPILE_OFFSETS
+#define DECL_OFFSET(struct,field) this_should_not_happen_for_cross_fields
+#define DECL_OFFSET2(struct,field,offset) \
+	 if ((int)G_STRUCT_OFFSET (struct, field) != offset) { \
+		g_print (#struct ":" #field " invalid struct offset %d (expected %d)\n",	\
+			offset,	\
+			(int)G_STRUCT_OFFSET (struct, field));	\
+		is_broken = TRUE;	\
+	}
+#define DECL_ALIGN(name,type) this_should_not_happen_for_cross_align
+#define DECL_ALIGN2(name,size) \
+	 if (MONO_ALIGN_ ## name != size) { \
+		g_print (#name ": invalid alignment %d (expected %d)\n",	\
+		size,	\
+		MONO_ALIGN_ ## name);	\
+		is_broken = TRUE;	\
+	}
+#define DECL_SIZE(type) this_should_not_happen_for_cross_size
+#define DECL_SIZE2(name,size) \
+	 if (MONO_SIZEOF_ ## name != size) { \
+		g_print (#name ": invalid size %d (expected %d)\n",	\
+		size,	\
+		MONO_SIZEOF_ ## name);	\
+		is_broken = TRUE;	\
+	}
+
+#include <mono/metadata/object-offsets.h>
+
+	g_assert (!is_broken);
+#endif
+}