diff --git a/xen/Makefile b/xen/Makefile
index 643c689658..2a689b26a2 100644
--- a/xen/Makefile
+++ b/xen/Makefile
@@ -118,6 +118,64 @@ $(KCONFIG_CONFIG):
 include/config/%.conf include/config/%.conf.cmd: $(KCONFIG_CONFIG)
 	$(MAKE) $(kconfig) syncconfig
 
+ifeq ($(CONFIG_DEBUG),y)
+CFLAGS += -O1
+else
+CFLAGS += -O2
+endif
+
+ifeq ($(CONFIG_FRAME_POINTER),y)
+CFLAGS += -fno-omit-frame-pointer
+else
+CFLAGS += -fomit-frame-pointer
+endif
+
+CFLAGS += -nostdinc -fno-builtin -fno-common
+CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
+$(call cc-option-add,CFLAGS,CC,-Wvla)
+CFLAGS += -pipe -D__XEN__ -include $(BASEDIR)/include/xen/config.h
+CFLAGS-$(CONFIG_DEBUG_INFO) += -g
+
+ifneq ($(CONFIG_CC_IS_CLANG),y)
+# Clang doesn't understand this command line argument, and doesn't appear to
+# have a suitable alternative.  The resulting compiled binary does function,
+# but has an excessively large symbol table.
+CFLAGS += -Wa,--strip-local-absolute
+endif
+
+AFLAGS += -D__ASSEMBLY__
+
+CFLAGS += $(CFLAGS-y)
+# allow extra CFLAGS externally via EXTRA_CFLAGS_XEN_CORE
+CFLAGS += $(EXTRA_CFLAGS_XEN_CORE)
+
+# Most CFLAGS are safe for assembly files:
+#  -std=gnu{89,99} gets confused by #-prefixed end-of-line comments
+#  -flto makes no sense and annoys clang
+AFLAGS += $(filter-out -std=gnu% -flto,$(CFLAGS)) $(AFLAGS-y)
+
+# LDFLAGS are only passed directly to $(LD)
+LDFLAGS += $(LDFLAGS_DIRECT) $(LDFLAGS-y)
+
+ifeq ($(CONFIG_UBSAN),y)
+CFLAGS_UBSAN := -fsanitize=undefined
+else
+CFLAGS_UBSAN :=
+endif
+
+ifeq ($(CONFIG_LTO),y)
+CFLAGS += -flto
+LDFLAGS-$(CONFIG_CC_IS_CLANG) += -plugin LLVMgold.so
+endif
+
+include $(BASEDIR)/arch/$(TARGET_ARCH)/arch.mk
+
+# define new variables to avoid the ones defined in Config.mk
+export XEN_CFLAGS := $(CFLAGS)
+export XEN_AFLAGS := $(AFLAGS)
+export XEN_LDFLAGS := $(LDFLAGS)
+export CFLAGS_UBSAN
+
 endif # need-config
 
 .PHONY: build install uninstall clean distclean MAP
diff --git a/xen/Rules.mk b/xen/Rules.mk
index 3408a35dbf..8e4b9e3a4a 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -38,59 +38,17 @@ ALL_OBJS-y               += $(BASEDIR)/arch/$(TARGET_ARCH)/built_in.o
 ALL_OBJS-$(CONFIG_CRYPTO)   += $(BASEDIR)/crypto/built_in.o
 
 # Initialise some variables
-CFLAGS_UBSAN :=
-
-ifeq ($(CONFIG_DEBUG),y)
-CFLAGS += -O1
-else
-CFLAGS += -O2
-endif
-
-ifeq ($(CONFIG_FRAME_POINTER),y)
-CFLAGS += -fno-omit-frame-pointer
-else
-CFLAGS += -fomit-frame-pointer
-endif
-
-CFLAGS += -nostdinc -fno-builtin -fno-common
-CFLAGS += -Werror -Wredundant-decls -Wno-pointer-arith
-$(call cc-option-add,CFLAGS,CC,-Wvla)
-CFLAGS += -pipe -D__XEN__ -include $(BASEDIR)/include/xen/config.h
-CFLAGS-$(CONFIG_DEBUG_INFO) += -g
-
-ifneq ($(CONFIG_CC_IS_CLANG),y)
-# Clang doesn't understand this command line argument, and doesn't appear to
-# have an suitable alternative.  The resulting compiled binary does function,
-# but has an excessively large symbol table.
-CFLAGS += -Wa,--strip-local-absolute
-endif
-
-AFLAGS += -D__ASSEMBLY__
+CFLAGS-y :=
+AFLAGS-y :=
 
 ALL_OBJS := $(ALL_OBJS-y)
 
-CFLAGS += $(CFLAGS-y)
-# allow extra CFLAGS externally via EXTRA_CFLAGS_XEN_CORE
-CFLAGS += $(EXTRA_CFLAGS_XEN_CORE)
-
-# Most CFLAGS are safe for assembly files:
-#  -std=gnu{89,99} gets confused by #-prefixed end-of-line comments
-#  -flto makes no sense and annoys clang
-AFLAGS += $(filter-out -std=gnu% -flto,$(CFLAGS))
-
-# LDFLAGS are only passed directly to $(LD)
-LDFLAGS += $(LDFLAGS_DIRECT)
-
-LDFLAGS += $(LDFLAGS-y)
-
 SPECIAL_DATA_SECTIONS := rodata $(foreach a,1 2 4 8 16, \
                                             $(foreach w,1 2 4, \
                                                         rodata.str$(w).$(a)) \
                                             rodata.cst$(a)) \
                          $(foreach r,rel rel.ro,data.$(r).local)
 
-include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
-
 include Makefile
 
 define gendep
@@ -107,7 +65,7 @@ $(foreach o,$(filter-out %/,$(obj-y) $(obj-bin-y) $(extra-y)),$(eval $(call gend
 subdir-y := $(subdir-y) $(filter %/, $(obj-y))
 obj-y    := $(patsubst %/, %/built_in.o, $(obj-y))
 
-$(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS += -DINIT_SECTIONS_ONLY
+$(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y += -DINIT_SECTIONS_ONLY
 
 ifeq ($(CONFIG_COVERAGE),y)
 ifeq ($(CONFIG_CC_IS_CLANG),y)
@@ -115,19 +73,16 @@ ifeq ($(CONFIG_CC_IS_CLANG),y)
 else
     COV_FLAGS := -fprofile-arcs -ftest-coverage
 endif
-$(filter-out %.init.o $(nocov-y),$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS += $(COV_FLAGS)
+$(filter-out %.init.o $(nocov-y),$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y += $(COV_FLAGS)
 endif
 
 ifeq ($(CONFIG_UBSAN),y)
-CFLAGS_UBSAN += -fsanitize=undefined
 # Any -fno-sanitize= options need to come after any -fsanitize= options
 $(filter-out %.init.o $(noubsan-y),$(obj-y) $(obj-bin-y) $(extra-y)): \
-CFLAGS += $(filter-out -fno-%,$(CFLAGS_UBSAN)) $(filter -fno-%,$(CFLAGS_UBSAN))
+CFLAGS-y += $(filter-out -fno-%,$(CFLAGS_UBSAN)) $(filter -fno-%,$(CFLAGS_UBSAN))
 endif
 
 ifeq ($(CONFIG_LTO),y)
-CFLAGS += -flto
-LDFLAGS-$(CONFIG_CC_IS_CLANG) += -plugin LLVMgold.so
 # Would like to handle all object files as bitcode, but objects made from
 # pure asm are in a different format and have to be collected separately.
 # Mirror the directory tree, collecting them as built_in_bin.o.
@@ -140,10 +95,18 @@ obj-bin-y :=
 endif
 
 # Always build obj-bin files as binary even if they come from C source. 
-$(obj-bin-y): CFLAGS := $(filter-out -flto,$(CFLAGS))
+$(obj-bin-y): XEN_CFLAGS := $(filter-out -flto,$(XEN_CFLAGS))
 
-c_flags = -MMD -MP -MF $(@D)/.$(@F).d $(CFLAGS) '-D__OBJECT_FILE__="$@"'
-a_flags = -MMD -MP -MF $(@D)/.$(@F).d $(AFLAGS)
+# Calculation of flags, first the generic flags, then the arch specific flags,
+# and last the flags modified for a target or a directory.
+
+c_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_CFLAGS) '-D__OBJECT_FILE__="$@"'
+a_flags = -MMD -MP -MF $(@D)/.$(@F).d $(XEN_AFLAGS)
+
+include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
+
+c_flags += $(CFLAGS-y)
+a_flags += $(CFLAGS-y) $(AFLAGS-y)
 
 built_in.o: $(obj-y) $(extra-y)
 ifeq ($(obj-y),)
@@ -152,7 +115,7 @@ else
 ifeq ($(CONFIG_LTO),y)
 	$(LD_LTO) -r -o $@ $(filter-out $(extra-y),$^)
 else
-	$(LD) $(LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
 endif
 endif
 
@@ -160,7 +123,7 @@ built_in_bin.o: $(obj-bin-y) $(extra-y)
 ifeq ($(obj-bin-y),)
 	$(CC) $(a_flags) -c -x assembler /dev/null -o $@
 else
-	$(LD) $(LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
 endif
 
 # Force execution of pattern rules (for which PHONY cannot be directly used).
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 913f6cdeed..9f1ab23357 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -95,24 +95,24 @@ prelink_lto.o: $(ALL_OBJS)
 
 # Link it with all the binary objects
 prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
 else
 prelink.o: $(ALL_OBJS)
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
 endif
 
 $(TARGET)-syms: prelink.o xen.lds
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o \
 	    $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
 	$(NM) -pa --format=sysv $(@D)/.$(@F).0 \
 		| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort >$(@D)/.$(@F).0.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o \
 	    $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
 	$(NM) -pa --format=sysv $(@D)/.$(@F).1 \
 		| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort >$(@D)/.$(@F).1.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
 	    $(@D)/.$(@F).1.o -o $@
 	$(NM) -pa --format=sysv $(@D)/$(@F) \
 		| $(BASEDIR)/tools/symbols --xensyms --sysv --sort \
diff --git a/xen/arch/arm/Rules.mk b/xen/arch/arm/Rules.mk
index 3ad284aa71..e69de29bb2 100644
--- a/xen/arch/arm/Rules.mk
+++ b/xen/arch/arm/Rules.mk
@@ -1,23 +0,0 @@
-########################################
-# arm-specific definitions
-
-#
-# If you change any of these configuration options then you must
-# 'make clean' before rebuilding.
-#
-
-CFLAGS += -I$(BASEDIR)/include
-
-$(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
-$(call cc-option-add,CFLAGS,CC,-Wnested-externs)
-
-# Prevent floating-point variables from creeping into Xen.
-CFLAGS-$(CONFIG_ARM_32) += -msoft-float
-CFLAGS-$(CONFIG_ARM_32) += -mcpu=cortex-a15
-
-CFLAGS-$(CONFIG_ARM_64) += -mcpu=generic
-CFLAGS-$(CONFIG_ARM_64) += -mgeneral-regs-only # No fp registers etc
-
-ifneq ($(filter command line environment,$(origin CONFIG_EARLY_PRINTK)),)
-    $(error You must use 'make menuconfig' to enable/disable early printk now)
-endif
diff --git a/xen/arch/arm/arch.mk b/xen/arch/arm/arch.mk
new file mode 100644
index 0000000000..c8186f5828
--- /dev/null
+++ b/xen/arch/arm/arch.mk
@@ -0,0 +1,18 @@
+########################################
+# arm-specific definitions
+
+CFLAGS += -I$(BASEDIR)/include
+
+$(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
+$(call cc-option-add,CFLAGS,CC,-Wnested-externs)
+
+# Prevent floating-point variables from creeping into Xen.
+CFLAGS-$(CONFIG_ARM_32) += -msoft-float
+CFLAGS-$(CONFIG_ARM_32) += -mcpu=cortex-a15
+
+CFLAGS-$(CONFIG_ARM_64) += -mcpu=generic
+CFLAGS-$(CONFIG_ARM_64) += -mgeneral-regs-only # No fp registers etc
+
+ifneq ($(filter command line environment,$(origin CONFIG_EARLY_PRINTK)),)
+    $(error You must use 'make menuconfig' to enable/disable early printk now)
+endif
diff --git a/xen/arch/arm/efi/Makefile b/xen/arch/arm/efi/Makefile
index d34c916891..e3ff2c3f28 100644
--- a/xen/arch/arm/efi/Makefile
+++ b/xen/arch/arm/efi/Makefile
@@ -1,4 +1,4 @@
-CFLAGS += -fshort-wchar
+CFLAGS-y += -fshort-wchar
 
 obj-y +=  boot.init.o runtime.o
 obj-$(CONFIG_ACPI) +=  efi-dom0.init.o
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 1405525105..a805e9982e 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -121,32 +121,32 @@ prelink-efi_lto.o: $(ALL_OBJS) efi/runtime.o efi/compat.o
 
 # Link it with all the binary objects
 prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
 
 prelink-efi.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink-efi_lto.o efi/boot.init.o
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
 else
 prelink.o: $(ALL_OBJS)
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
 
 prelink-efi.o: $(ALL_OBJS) efi/boot.init.o efi/runtime.o efi/compat.o
-	$(LD) $(LDFLAGS) -r -o $@ $(filter-out %/efi/built_in.o,$^)
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out %/efi/built_in.o,$^)
 endif
 
 $(TARGET)-syms: prelink.o xen.lds
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
 	    $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
 	$(NM) -pa --format=sysv $(@D)/.$(@F).0 \
 		| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort \
 		>$(@D)/.$(@F).0.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
 	    $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
 	$(NM) -pa --format=sysv $(@D)/.$(@F).1 \
 		| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort $(syms-warn-dup-y) \
 		>$(@D)/.$(@F).1.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
-	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
+	$(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
 	    $(@D)/.$(@F).1.o -o $@
 	$(NM) -pa --format=sysv $(@D)/$(@F) \
 		| $(BASEDIR)/tools/symbols --xensyms --sysv --sort \
@@ -159,7 +159,7 @@ note.o: $(TARGET)-syms
 		--rename-section=.data=.note.gnu.build-id -S $@.bin $@
 	rm -f $@.bin
 
-EFI_LDFLAGS = $(patsubst -m%,-mi386pep,$(LDFLAGS)) --subsystem=10
+EFI_LDFLAGS = $(patsubst -m%,-mi386pep,$(XEN_LDFLAGS)) --subsystem=10
 EFI_LDFLAGS += --image-base=$(1) --stack=0,0 --heap=0,0 --strip-debug
 EFI_LDFLAGS += --section-alignment=0x200000 --file-alignment=0x20
 EFI_LDFLAGS += --major-image-version=$(XEN_VERSION)
@@ -168,7 +168,7 @@ EFI_LDFLAGS += --major-os-version=2 --minor-os-version=0
 EFI_LDFLAGS += --major-subsystem-version=2 --minor-subsystem-version=0
 
 # Check if the compiler supports the MS ABI.
-export XEN_BUILD_EFI := $(shell $(CC) $(CFLAGS) -c efi/check.c -o efi/check.o 2>/dev/null && echo y)
+export XEN_BUILD_EFI := $(shell $(CC) $(XEN_CFLAGS) -c efi/check.c -o efi/check.o 2>/dev/null && echo y)
 # Check if the linker supports PE.
 XEN_BUILD_PE := $(if $(XEN_BUILD_EFI),$(shell $(LD) -mi386pep --subsystem=10 -o efi/check.efi efi/check.o 2>/dev/null && echo y))
 CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_EFI
@@ -178,7 +178,7 @@ $(TARGET).efi: ALT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A ALT_
 
 ifneq ($(build_id_linker),)
 ifeq ($(call ld-ver-build-id,$(LD) $(filter -m%,$(EFI_LDFLAGS))),y)
-CFLAGS += -DBUILD_ID_EFI
+CFLAGS-y += -DBUILD_ID_EFI
 EFI_LDFLAGS += $(build_id_linker)
 note_file := efi/buildid.o
 # NB: this must be the last input in the linker call, because inputs following
@@ -225,7 +225,7 @@ efi/boot.init.o efi/runtime.o efi/compat.o efi/buildid.o efi/relocs-dummy.o: ;
 asm-offsets.s: $(TARGET_SUBARCH)/asm-offsets.c $(BASEDIR)/include/asm-x86/asm-macros.h
 	$(CC) $(filter-out -Wa$(comma)% -flto,$(c_flags)) -S -o $@ $<
 
-asm-macros.i: CFLAGS += -D__ASSEMBLY__ -P
+asm-macros.i: CFLAGS-y += -D__ASSEMBLY__ -P
 
 $(BASEDIR)/include/asm-x86/asm-macros.h: asm-macros.i Makefile
 	echo '#if 0' >$@.new
@@ -238,7 +238,7 @@ $(BASEDIR)/include/asm-x86/asm-macros.h: asm-macros.i Makefile
 	echo '#endif' >>$@.new
 	$(call move-if-changed,$@.new,$@)
 
-efi.lds: AFLAGS += -DEFI
+efi.lds: AFLAGS-y += -DEFI
 xen.lds efi.lds: xen.lds.S
 	$(CC) -P -E -Ui386 $(filter-out -Wa$(comma)%,$(a_flags)) -o $@ $<
 	sed -e 's/.*\.lds\.o:/$(@F):/g' <.$(@F).d >.$(@F).d.new
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index 4b7ab78467..56fe22c979 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -1,89 +1,10 @@
 ########################################
 # x86-specific definitions
 
-XEN_IMG_OFFSET := 0x200000
-
-CFLAGS += -I$(BASEDIR)/include
-CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-generic
-CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-default
-CFLAGS += -DXEN_IMG_OFFSET=$(XEN_IMG_OFFSET)
-CFLAGS += '-D__OBJECT_LABEL__=$(subst /,$$,$(subst -,_,$(subst $(BASEDIR)/,,$(CURDIR))/$@))'
-
-# Prevent floating-point variables from creeping into Xen.
-CFLAGS += -msoft-float
-
-ifeq ($(CONFIG_CC_IS_CLANG),y)
-# Note: Any test which adds -no-integrated-as will cause subsequent tests to
-# succeed, and not trigger further additions.
-#
-# The tests to select whether the integrated assembler is usable need to happen
-# before testing any assembler features, or else the result of the tests would
-# be stale if the integrated assembler is not used.
-
-# Older clang's built-in assembler doesn't understand .skip with labels:
-# https://bugs.llvm.org/show_bug.cgi?id=27369
-$(call as-option-add,CFLAGS,CC,".L0: .L1: .skip (.L1 - .L0)",,\
-                     -no-integrated-as)
-
-# Check whether clang asm()-s support .include.
-$(call as-option-add,CFLAGS,CC,".include \"asm-x86/indirect_thunk_asm.h\"",,\
-                     -no-integrated-as)
-
-# Check whether clang keeps .macro-s between asm()-s:
-# https://bugs.llvm.org/show_bug.cgi?id=36110
-$(call as-option-add,CFLAGS,CC,\
-                     ".macro FOO;.endm"$$(close); asm volatile $$(open)".macro FOO;.endm",\
-                     -no-integrated-as)
+ifneq ($(filter -DHAVE_AS_QUOTED_SYM,$(XEN_CFLAGS)),)
+object_label_flags = '-D__OBJECT_LABEL__=$(subst $(BASEDIR)/,,$(CURDIR))/$@'
+else
+object_label_flags = '-D__OBJECT_LABEL__=$(subst /,$$,$(subst -,_,$(subst $(BASEDIR)/,,$(CURDIR))/$@))'
 endif
-
-$(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
-$(call cc-option-add,CFLAGS,CC,-Wnested-externs)
-$(call as-option-add,CFLAGS,CC,"vmcall",-DHAVE_AS_VMX)
-$(call as-option-add,CFLAGS,CC,"crc32 %eax$$(comma)%eax",-DHAVE_AS_SSE4_2)
-$(call as-option-add,CFLAGS,CC,"invept (%rax)$$(comma)%rax",-DHAVE_AS_EPT)
-$(call as-option-add,CFLAGS,CC,"rdrand %eax",-DHAVE_AS_RDRAND)
-$(call as-option-add,CFLAGS,CC,"rdfsbase %rax",-DHAVE_AS_FSGSBASE)
-$(call as-option-add,CFLAGS,CC,"xsaveopt (%rax)",-DHAVE_AS_XSAVEOPT)
-$(call as-option-add,CFLAGS,CC,"rdseed %eax",-DHAVE_AS_RDSEED)
-$(call as-option-add,CFLAGS,CC,"clwb (%rax)",-DHAVE_AS_CLWB)
-$(call as-option-add,CFLAGS,CC,".equ \"x\"$$(comma)1", \
-                     -U__OBJECT_LABEL__ -DHAVE_AS_QUOTED_SYM \
-                     '-D__OBJECT_LABEL__=$(subst $(BASEDIR)/,,$(CURDIR))/$$@')
-$(call as-option-add,CFLAGS,CC,"invpcid (%rax)$$(comma)%rax",-DHAVE_AS_INVPCID)
-
-# GAS's idea of true is -1.  Clang's idea is 1
-$(call as-option-add,CFLAGS,CC,\
-    ".if ((1 > 0) < 0); .error \"\";.endif",,-DHAVE_AS_NEGATIVE_TRUE)
-
-# Check to see whether the assmbler supports the .nop directive.
-$(call as-option-add,CFLAGS,CC,\
-    ".L1: .L2: .nops (.L2 - .L1)$$(comma)9",-DHAVE_AS_NOPS_DIRECTIVE)
-
-CFLAGS += -mno-red-zone -fpic -fno-asynchronous-unwind-tables
-
-# Xen doesn't use SSE interally.  If the compiler supports it, also skip the
-# SSE setup for variadic function calls.
-CFLAGS += -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
-
-# Compile with thunk-extern, indirect-branch-register if avaiable.
-ifeq ($(CONFIG_INDIRECT_THUNK),y)
-CFLAGS += -mindirect-branch=thunk-extern -mindirect-branch-register
-CFLAGS += -fno-jump-tables
-endif
-
-# If supported by the compiler, reduce stack alignment to 8 bytes. But allow
-# this to be overridden elsewhere.
-$(call cc-option-add,CFLAGS-stack-boundary,CC,-mpreferred-stack-boundary=3)
-CFLAGS += $(CFLAGS-stack-boundary)
-
-ifeq ($(CONFIG_UBSAN),y)
-# Don't enable alignment sanitisation.  x86 has efficient unaligned accesses,
-# and various things (ACPI tables, hypercall pages, stubs, etc) are wont-fix.
-# It also causes an as-yet-unidentified crash on native boot before the
-# console starts.
-$(call cc-option-add,CFLAGS_UBSAN,CC,-fno-sanitize=alignment)
-endif
-
-# Set up the assembler include path properly for older toolchains.
-CFLAGS += -Wa,-I$(BASEDIR)/include
-
+c_flags += $(object_label_flags) $(CFLAGS-stack-boundary)
+a_flags += $(object_label_flags) $(CFLAGS-stack-boundary)
diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
new file mode 100644
index 0000000000..2a51553edb
--- /dev/null
+++ b/xen/arch/x86/arch.mk
@@ -0,0 +1,84 @@
+########################################
+# x86-specific definitions
+
+export XEN_IMG_OFFSET := 0x200000
+
+CFLAGS += -I$(BASEDIR)/include
+CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-generic
+CFLAGS += -I$(BASEDIR)/include/asm-x86/mach-default
+CFLAGS += -DXEN_IMG_OFFSET=$(XEN_IMG_OFFSET)
+
+# Prevent floating-point variables from creeping into Xen.
+CFLAGS += -msoft-float
+
+ifeq ($(CONFIG_CC_IS_CLANG),y)
+# Note: Any test which adds -no-integrated-as will cause subsequent tests to
+# succeed, and not trigger further additions.
+#
+# The tests to select whether the integrated assembler is usable need to happen
+# before testing any assembler features, or else the result of the tests would
+# be stale if the integrated assembler is not used.
+
+# Older clang's built-in assembler doesn't understand .skip with labels:
+# https://bugs.llvm.org/show_bug.cgi?id=27369
+$(call as-option-add,CFLAGS,CC,".L0: .L1: .skip (.L1 - .L0)",,\
+                     -no-integrated-as)
+
+# Check whether clang asm()-s support .include.
+$(call as-option-add,CFLAGS,CC,".include \"asm-x86/indirect_thunk_asm.h\"",,\
+                     -no-integrated-as)
+
+# Check whether clang keeps .macro-s between asm()-s:
+# https://bugs.llvm.org/show_bug.cgi?id=36110
+$(call as-option-add,CFLAGS,CC,\
+                     ".macro FOO;.endm"$$(close); asm volatile $$(open)".macro FOO;.endm",\
+                     -no-integrated-as)
+endif
+
+$(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
+$(call cc-option-add,CFLAGS,CC,-Wnested-externs)
+$(call as-option-add,CFLAGS,CC,"vmcall",-DHAVE_AS_VMX)
+$(call as-option-add,CFLAGS,CC,"crc32 %eax$$(comma)%eax",-DHAVE_AS_SSE4_2)
+$(call as-option-add,CFLAGS,CC,"invept (%rax)$$(comma)%rax",-DHAVE_AS_EPT)
+$(call as-option-add,CFLAGS,CC,"rdrand %eax",-DHAVE_AS_RDRAND)
+$(call as-option-add,CFLAGS,CC,"rdfsbase %rax",-DHAVE_AS_FSGSBASE)
+$(call as-option-add,CFLAGS,CC,"xsaveopt (%rax)",-DHAVE_AS_XSAVEOPT)
+$(call as-option-add,CFLAGS,CC,"rdseed %eax",-DHAVE_AS_RDSEED)
+$(call as-option-add,CFLAGS,CC,"clwb (%rax)",-DHAVE_AS_CLWB)
+$(call as-option-add,CFLAGS,CC,".equ \"x\"$$(comma)1",-DHAVE_AS_QUOTED_SYM)
+$(call as-option-add,CFLAGS,CC,"invpcid (%rax)$$(comma)%rax",-DHAVE_AS_INVPCID)
+
+# GAS's idea of true is -1.  Clang's idea is 1
+$(call as-option-add,CFLAGS,CC,\
+    ".if ((1 > 0) < 0); .error \"\";.endif",,-DHAVE_AS_NEGATIVE_TRUE)
+
+# Check to see whether the assmbler supports the .nop directive.
+$(call as-option-add,CFLAGS,CC,\
+    ".L1: .L2: .nops (.L2 - .L1)$$(comma)9",-DHAVE_AS_NOPS_DIRECTIVE)
+
+CFLAGS += -mno-red-zone -fpic -fno-asynchronous-unwind-tables
+
+# Xen doesn't use SSE interally.  If the compiler supports it, also skip the
+# SSE setup for variadic function calls.
+CFLAGS += -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
+
+# Compile with thunk-extern, indirect-branch-register if avaiable.
+CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch=thunk-extern
+CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch-register
+CFLAGS-$(CONFIG_INDIRECT_THUNK) += -fno-jump-tables
+
+# If supported by the compiler, reduce stack alignment to 8 bytes. But allow
+# this to be overridden elsewhere.
+$(call cc-option-add,CFLAGS-stack-boundary,CC,-mpreferred-stack-boundary=3)
+export CFLAGS-stack-boundary
+
+ifeq ($(CONFIG_UBSAN),y)
+# Don't enable alignment sanitisation.  x86 has efficient unaligned accesses,
+# and various things (ACPI tables, hypercall pages, stubs, etc) are wont-fix.
+# It also causes an as-yet-unidentified crash on native boot before the
+# console starts.
+$(call cc-option-add,CFLAGS_UBSAN,CC,-fno-sanitize=alignment)
+endif
+
+# Set up the assembler include path properly for older toolchains.
+CFLAGS += -Wa,-I$(BASEDIR)/include
diff --git a/xen/arch/x86/efi/Makefile b/xen/arch/x86/efi/Makefile
index 4bc0a196e9..490d791aae 100644
--- a/xen/arch/x86/efi/Makefile
+++ b/xen/arch/x86/efi/Makefile
@@ -1,4 +1,4 @@
-CFLAGS += -fshort-wchar
+CFLAGS-y += -fshort-wchar
 
 %.o: %.ihex
 	$(OBJCOPY) -I ihex -O binary $< $@
diff --git a/xen/common/libelf/Makefile b/xen/common/libelf/Makefile
index 3d9e38f27e..464c448d9d 100644
--- a/xen/common/libelf/Makefile
+++ b/xen/common/libelf/Makefile
@@ -3,10 +3,10 @@ nocov-y += libelf.o
 
 SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
 
-CFLAGS += -Wno-pointer-sign
+CFLAGS-y += -Wno-pointer-sign
 
 libelf.o: libelf-temp.o Makefile
 	$(OBJCOPY) $(foreach s,$(SECTIONS),--rename-section .$(s)=.init.$(s)) $< $@
 
 libelf-temp.o: libelf-tools.o libelf-loader.o libelf-dominfo.o #libelf-relocate.o
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
diff --git a/xen/common/libfdt/Makefile b/xen/common/libfdt/Makefile
index c075bbf546..e2a5e59380 100644
--- a/xen/common/libfdt/Makefile
+++ b/xen/common/libfdt/Makefile
@@ -5,10 +5,10 @@ SECTIONS := text data $(SPECIAL_DATA_SECTIONS)
 obj-y += libfdt.o
 nocov-y += libfdt.o
 
-CFLAGS += -I$(BASEDIR)/include/xen/libfdt/
+CFLAGS-y += -I$(BASEDIR)/include/xen/libfdt/
 
 libfdt.o: libfdt-temp.o Makefile
 	$(OBJCOPY) $(foreach s,$(SECTIONS),--rename-section .$(s)=.init.$(s)) $< $@
 
 libfdt-temp.o: $(LIBFDT_OBJS)
-	$(LD) $(LDFLAGS) -r -o $@ $^
+	$(LD) $(XEN_LDFLAGS) -r -o $@ $^
diff --git a/xen/include/Makefile b/xen/include/Makefile
index a488a98d8b..2a10725d68 100644
--- a/xen/include/Makefile
+++ b/xen/include/Makefile
@@ -64,7 +64,7 @@ compat/%.h: compat/%.i Makefile $(BASEDIR)/tools/compat-build-header.py
 	mv -f $@.new $@
 
 compat/%.i: compat/%.c Makefile
-	$(CPP) $(filter-out -Wa$(comma)% -include %/include/xen/config.h,$(CFLAGS)) $(cppflags-y) -o $@ $<
+	$(CPP) $(filter-out -Wa$(comma)% -include %/include/xen/config.h,$(XEN_CFLAGS)) $(cppflags-y) -o $@ $<
 
 compat/%.c: public/%.h xlat.lst Makefile $(BASEDIR)/tools/compat-build-source.py
 	mkdir -p $(@D)
diff --git a/xen/xsm/flask/Makefile b/xen/xsm/flask/Makefile
index f001bb18d4..6db396347b 100644
--- a/xen/xsm/flask/Makefile
+++ b/xen/xsm/flask/Makefile
@@ -4,7 +4,7 @@ obj-y += flask_op.o
 
 obj-y += ss/
 
-CFLAGS += -I./include
+CFLAGS-y += -I./include
 
 AWK = awk
 
diff --git a/xen/xsm/flask/ss/Makefile b/xen/xsm/flask/ss/Makefile
index 046ce8f533..d32b9e0713 100644
--- a/xen/xsm/flask/ss/Makefile
+++ b/xen/xsm/flask/ss/Makefile
@@ -8,4 +8,4 @@ obj-y += services.o
 obj-y += conditional.o
 obj-y += mls.o
 
-CFLAGS += -I../include
+CFLAGS-y += -I../include