[PATCH v3 1/4] x86/EFI: sanitize build logic

[Jan Beulich <jbeulich@xxxxxxxx>]

With changes done over time and as far as linking goes, the only special
things about building with EFI support enabled are
- the need for the dummy relocations object for xen.gz uniformly in all
  build stages,
- the special efi/buildid.o file, which can't be made part of
  efi/built_in.o, due to the extra linker options required for it.
All other efi/*.o can be consumed from the built_in*.o files.

In efi/Makefile, besides moving relocs-dummy.o to "extra", also properly
split between obj-y and obj-bin-y.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v3: Fix efi/buildid.o dependency handling.
v2: Drop a now stale piece of Makefile logic.

--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -113,28 +113,35 @@ $(TARGET): $(TARGET)-syms $(efi-y) boot/
                { echo "No Multiboot2 header found" >&2; false; }
        mv $(TMP) $(TARGET)
 
+# Check if the compiler supports the MS ABI.
+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
+
 ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o 
$(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
+EFI_OBJS-$(XEN_BUILD_EFI) := efi/relocs-dummy.o
 
 ifeq ($(CONFIG_LTO),y)
 # Gather all LTO objects together
 prelink_lto.o: $(ALL_OBJS)
        $(LD_LTO) -r -o $@ $^
 
-prelink-efi_lto.o: $(ALL_OBJS) efi/runtime.o efi/compat.o
-       $(LD_LTO) -r -o $@ $(filter-out %/efi/built_in.o,$^)
+prelink-efi_lto.o: $(ALL_OBJS)
+       $(LD_LTO) -r -o $@ $^
 
 # Link it with all the binary objects
-prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
+prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o 
$(EFI_OBJS-y)
        $(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
+prelink-efi.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) 
prelink-efi_lto.o
        $(LD) $(XEN_LDFLAGS) -r -o $@ $^
 else
-prelink.o: $(ALL_OBJS)
+prelink.o: $(ALL_OBJS) $(EFI_OBJS-y)
        $(LD) $(XEN_LDFLAGS) -r -o $@ $^
 
-prelink-efi.o: $(ALL_OBJS) efi/boot.init.o efi/runtime.o efi/compat.o
-       $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out %/efi/built_in.o,$^)
+prelink-efi.o: $(ALL_OBJS)
+       $(LD) $(XEN_LDFLAGS) -r -o $@ $^
 endif
 
 $(TARGET)-syms: prelink.o xen.lds
@@ -171,12 +178,6 @@ EFI_LDFLAGS += --minor-image-version=$(X
 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) $(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
-
 $(TARGET).efi: VIRT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A 
VIRT_START$$,,p')
 $(TARGET).efi: ALT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A 
ALT_START$$,,p')
 
@@ -185,6 +186,8 @@ ifeq ($(call ld-ver-build-id,$(LD) $(fil
 CFLAGS-y += -DBUILD_ID_EFI
 EFI_LDFLAGS += $(build_id_linker)
 note_file := efi/buildid.o
+efi/buildid.o: $(BASEDIR)/arch/x86/efi/built_in.o
+efi/buildid.o: ;
 # NB: this must be the last input in the linker call, because inputs following
 # the -b option will all be treated as being in the specified format.
 note_file_option := -b pe-x86-64 $(note_file)
@@ -223,9 +226,6 @@ $(TARGET).efi: FORCE
        echo '$(if $(filter y,$(XEN_BUILD_EFI)),xen.efi generation,EFI support) 
disabled'
 endif
 
-efi/boot.init.o efi/runtime.o efi/compat.o efi/buildid.o efi/relocs-dummy.o: 
$(BASEDIR)/arch/x86/efi/built_in.o
-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 $@ $<
 
--- a/xen/arch/x86/efi/Makefile
+++ b/xen/arch/x86/efi/Makefile
@@ -14,6 +14,7 @@ $(call cc-option-add,cflags-stack-bounda
 $(EFIOBJ): CFLAGS-stack-boundary := $(cflags-stack-boundary)
 
 obj-y := stub.o
-obj-$(XEN_BUILD_EFI) := $(EFIOBJ) relocs-dummy.o
-extra-$(XEN_BUILD_EFI) += buildid.o
+obj-$(XEN_BUILD_EFI) := $(filter-out %.init.o,$(EFIOBJ))
+obj-bin-$(XEN_BUILD_EFI) := $(filter %.init.o,$(EFIOBJ))
+extra-$(XEN_BUILD_EFI) += buildid.o relocs-dummy.o
 nocov-$(XEN_BUILD_EFI) += stub.o