Add support for AArch64 XOM binaries.

Adds build system support for generating AArch64 binaries with
execute-only memory layouts via a new LOCAL_XOM property. Also adds
support for an ENABLE_XOM build flag for global builds.

Bug: 77958880
Test: make -j ENABLE_XOM=true
Change-Id: I6af9e3615d0a9fdff802eae50e6ad94311ec8046

core/binary.mk

@@ -73,6 +73,30 @@ else
   my_native_coverage := false
 endif
 
+ifeq ($(strip $(ENABLE_XOM)),true)
+  ifndef LOCAL_IS_HOST_MODULE
+    my_xom := true
+    # Disable XOM in excluded paths.
+    combined_xom_exclude_paths := $(XOM_EXCLUDE_PATHS) \
+                                  $(PRODUCT_XOM_EXCLUDE_PATHS)
+    ifneq ($(strip $(foreach dir,$(subst $(comma),$(space),$(combined_xom_exclude_paths)),\
+           $(filter $(dir)%,$(LOCAL_PATH)))),)
+      my_xom := false
+    endif
+
+    # Allow LOCAL_XOM to override the above
+    ifdef LOCAL_XOM
+      my_xom := $(LOCAL_XOM)
+    endif
+
+    ifeq ($(strip $(my_xom)),true)
+      ifeq (arm64,$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH))
+        my_ldflags += -Wl,-execute-only
+      endif
+    endif
+  endif
+endif
+
 my_allow_undefined_symbols := $(strip $(LOCAL_ALLOW_UNDEFINED_SYMBOLS))
 ifdef SANITIZE_HOST
 ifdef LOCAL_IS_HOST_MODULE

core/clear_vars.mk

@@ -302,6 +302,7 @@ LOCAL_VTS_INCLUDES:=
 LOCAL_VTS_MODE:=
 LOCAL_WARNINGS_ENABLE:=
 LOCAL_WHOLE_STATIC_LIBRARIES:=
+LOCAL_XOM:=
 LOCAL_YACCFLAGS:=
 # TODO: deprecate, it does nothing
 OVERRIDE_BUILT_MODULE_PATH:=

core/product.mk

@@ -212,6 +212,7 @@ _product_var_list := \
     PRODUCT_USE_DYNAMIC_PARTITIONS \
     PRODUCT_RETROFIT_DYNAMIC_PARTITIONS \
     PRODUCT_OTA_ENFORCE_VINTF_KERNEL_REQUIREMENTS \
+    PRODUCT_XOM_EXCLUDE_PATHS \
 
 define dump-product
 $(info ==== $(1) ====)\

core/product_config.mk

@@ -501,6 +501,10 @@ PRODUCT_CFI_EXCLUDE_PATHS := \
 PRODUCT_CFI_INCLUDE_PATHS := \
     $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_CFI_INCLUDE_PATHS))
 
+# Whether any paths are excluded from being set XOM when ENABLE_XOM=true
+PRODUCT_XOM_EXCLUDE_PATHS := \
+    $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_XOM_EXCLUDE_PATHS))
+
 # which Soong namespaces to export to Make
 PRODUCT_SOONG_NAMESPACES := \
     $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SOONG_NAMESPACES))

core/soong_config.mk

@@ -82,6 +82,8 @@ $(call add_json_bool, Safestack,                         $(filter true,$(USE_SAF
 $(call add_json_bool, EnableCFI,                         $(call invert_bool,$(filter false,$(ENABLE_CFI))))
 $(call add_json_list, CFIExcludePaths,                   $(CFI_EXCLUDE_PATHS) $(PRODUCT_CFI_EXCLUDE_PATHS))
 $(call add_json_list, CFIIncludePaths,                   $(CFI_INCLUDE_PATHS) $(PRODUCT_CFI_INCLUDE_PATHS))
+$(call add_json_bool, EnableXOM,                         $(filter true,$(ENABLE_XOM)))
+$(call add_json_list, XOMExcludePaths,                   $(XOM_EXCLUDE_PATHS) $(PRODUCT_XOM_EXCLUDE_PATHS))
 $(call add_json_list, IntegerOverflowExcludePaths,       $(INTEGER_OVERFLOW_EXCLUDE_PATHS) $(PRODUCT_INTEGER_OVERFLOW_EXCLUDE_PATHS))
 
 $(call add_json_bool, ClangTidy,                         $(filter 1 true,$(WITH_TIDY)))