[PATCH v2 1/7] x86: split xen-syms/xen.efi linking rules

[Jan Beulich <jbeulich@xxxxxxxx>]

Doing so, besides (hopefully) adding clarity (not the least by way of
using pattern rules where possible), also avoids explicit recursive
$(MAKE) invocations. For xen-syms move re-usable helper rules to a new
scripts/Makefile.link.

While doing so, re-order .map file creation (which can in principle fail)
and check-endbr.sh invocation ahead of putting in place the final image
(which is now the result of a simple rename).

Also drop --source-name= from the tools/symbols invocation which has
--empty passed, for being meaningless there.

Note that the original "rm" at the end of the rule needs limiting:
Removing intermediate files (which $(MAKE) doesn't itself remove) would
cause re-linking even when installing as root (when common/version.o is
left unaltered, and hence an incremental build should do nothing as long
as nothing else changed in the source tree).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
I'd like to keep the "beautification" part, i.e. transforming to more use
of Kbuild.include machinery, separate.

The check-endbr.sh invocation doesn't fit neatly into this model. I was
considering to move it into $(TARGET)'s rule, but that's not very nice
either (both because it'd be odd [strictly speaking: wrong] for xen.efi,
and because it would reduce parallelism).
---
v2: Mark intermediate files as such. Don't use $(if_changed ...).

--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -102,12 +102,6 @@ notes_phdrs = --notes
 endif
 endif
 
-syms-warn-dup-y := --warn-dup
-syms-warn-dup-$(CONFIG_SUPPRESS_DUPLICATE_SYMBOL_WARNINGS) :=
-syms-warn-dup-$(CONFIG_ENFORCE_UNIQUE_SYMBOLS) := --error-dup
-
-orphan-handling-$(call ld-option,--orphan-handling=warn) += 
--orphan-handling=warn
-
 $(TARGET): TMP = $(dot-target).elf32
 $(TARGET): $(TARGET)-syms $(efi-y) $(obj)/boot/mkelf32
        $(obj)/boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(TMP) 
$(XEN_IMG_OFFSET)
@@ -119,31 +113,11 @@ $(TARGET): $(TARGET)-syms $(efi-y) $(obj
 
 CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_EFI
 
-$(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
-       $(objtree)/tools/symbols $(all_symbols) --empty > $(dot-target).0.S
-       $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) 
--strip-debug \
-             $(dot-target).0.o -o $(dot-target).0
-       $(NM) -pa --format=sysv $(dot-target).0 \
-               | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
-               > $(dot-target).1.S
-       $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) 
--strip-debug \
-           $(dot-target).1.o -o $(dot-target).1
-       $(NM) -pa --format=sysv $(dot-target).1 \
-               | $(objtree)/tools/symbols $(all_symbols) --sysv --sort 
$(syms-warn-dup-y) \
-               > $(dot-target).2.S
-       $(MAKE) $(build)=$(@D) $(dot-target).2.o
-       $(call compare-symbol-tables, $(dot-target).1.o, $(dot-target).2.o)
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
-           $(orphan-handling-y) $(dot-target).2.o -o $@
-       $(NM) -pa --format=sysv $@ \
-               | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
-               > $@.map
-       rm -f $(dot-target).[0-9]* $(@D)/..$(@F).[0-9]*
-ifeq ($(CONFIG_XEN_IBT),y)
-       $(SHELL) $(srctree)/tools/check-endbr.sh $@
-endif
+LAST_LINKING_PASS := 2
+
+final-image-check-$(CONFIG_XEN_IBT) = $(SHELL) $(srctree)/tools/check-endbr.sh 
$<
+
+include scripts/Makefile.link
 
 $(obj)/note.o: $(TARGET)-syms
        $(OBJCOPY) -O binary --only-section=.note.gnu.build-id $< $@.bin
@@ -191,51 +165,69 @@ note_file_option ?= $(note_file)
 
 extra-$(XEN_BUILD_PE) += efi.lds
 ifeq ($(XEN_BUILD_PE),y)
-$(TARGET).efi: $(obj)/efi/relocs-dummy.o $(obj)/efi/relocs-empty.o 
$(obj)/efi/mkreloc
-$(TARGET).efi: $(objtree)/prelink.o $(note_file) $(obj)/efi.lds
+
+.INTERMEDIATE: $(addprefix .$(TARGET).efi., \
+                           $(foreach n, 0 1 2, \
+                                     $(n) alt.$(n) $(n)r.o $(n)s.o $(n)r.S 
$(n)s.S))
+
+.$(TARGET).efi.%.o: .$(TARGET).efi.%.S FORCE
+       $(call cmd,cc_o_S)
+
+.$(TARGET).efi.1r.S: .$(TARGET).efi.0 $(if 
$(relocs-dummy),.$(TARGET).efi.alt.0)
+.$(TARGET).efi.2r.S: .$(TARGET).efi.1 $(if 
$(relocs-dummy),.$(TARGET).efi.alt.1)
+
+.$(TARGET).efi.0r.o: $(obj)/efi/relocs-dummy.o $(obj)/efi/mkreloc
+       ln -sf $< $@
+
+.$(TARGET).efi.%r.S:
+       $(MKRELOC) $^ > $@
+
+.$(TARGET).efi.0s.S:
+       $(objtree)/tools/symbols $(all_symbols) --empty > $@
+
+.$(TARGET).efi.1s.S: .$(TARGET).efi.0
+.$(TARGET).efi.2s.S: .$(TARGET).efi.1
+
+.$(TARGET).efi.%s.S:
+       $(NM) -pa --format=sysv $< \
+         | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
+           --source-name=$(TARGET).efi.S \
+         > $@
+
+# See above for why $(note_file) needs removing here.
+efi-objs = $(filter-out $(note_file),$(filter %.o,$^))
+
+.$(TARGET).efi.%: $(objtree)/prelink.o .$(TARGET).efi.%r.o \
+                  .$(TARGET).efi.%s.o $(note_file) $(obj)/efi.lds
+       $(LD) $(call EFI_LDFLAGS,$(VIRT_BASE)) -T $(obj)/efi.lds $(efi-objs) \
+             --strip-debug $(note_file_option) -o $@
+
+.$(TARGET).efi.alt.%: $(objtree)/prelink.o .$(TARGET).efi.%r.o \
+                      .$(TARGET).efi.%s.o $(note_file) $(obj)/efi.lds
+       $(LD) $(call EFI_LDFLAGS,$(ALT_BASE)) -T $(obj)/efi.lds $(efi-objs) \
+             --strip-debug $(note_file_option) -o $@
+
+.$(TARGET).efi.2: $(objtree)/prelink.o $(obj)/efi/relocs-empty.o \
+                  .$(TARGET).efi.2r.o .$(TARGET).efi.2s.o $(note_file) \
+                  $(obj)/efi.lds
+       $(call compare-symbol-tables, .$(TARGET).efi.1r.o, .$(TARGET).efi.2r.o)
+       $(call compare-symbol-tables, .$(TARGET).efi.1s.o, .$(TARGET).efi.2s.o)
+       $(LD) $(call EFI_LDFLAGS,$(VIRT_BASE)) -T $(obj)/efi.lds $(efi-objs) \
+             $(orphan-handling-y) $(note_file_option) -o $@
+
+$(TARGET).efi: .$(TARGET).efi.2
 ifeq ($(CONFIG_DEBUG_INFO),y)
-       $(if $(filter --strip-debug,$(EFI_LDFLAGS)),echo,:) "Will strip debug 
info from $(@F)"
+       $(if $(filter --strip-debug,$(EFI_LDFLAGS)),echo,:) "No debug info in 
$(@F)"
 endif
-       $(objtree)/tools/symbols $(all_symbols) --source-name=$(@F).S --empty \
-               > $(dot-target).0s.S
-       $(MAKE) $(build)=$(@D) .$(@F).0s.o
-       $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
-                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $< 
$(relocs-dummy) \
-                       $(dot-target).0s.o $(note_file_option) --strip-debug \
-                       -o $(dot-target).$(base).0 &&) :
-       $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).0) \
-               > $(dot-target).1r.S
-       $(NM) -pa --format=sysv $(dot-target).$(VIRT_BASE).0 \
-               | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
-                  --source-name=$(@F).S \
-               > $(dot-target).1s.S
-       $(MAKE) $(build)=$(@D) .$(@F).1r.o .$(@F).1s.o
-       $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
-                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $<  
--strip-debug \
-                       $(dot-target).1r.o $(dot-target).1s.o 
$(note_file_option) \
-                       -o $(dot-target).$(base).1 &&) :
-       $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).1) \
-               > $(dot-target).2r.S
-       $(NM) -pa --format=sysv $(dot-target).$(VIRT_BASE).1 \
-               | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
-                  --source-name=$(@F).S \
-               > $(dot-target).2s.S
-       $(MAKE) $(build)=$(@D) .$(@F).2r.o .$(@F).2s.o
-       $(call compare-symbol-tables, $(dot-target).1r.o, $(dot-target).2r.o)
-       $(call compare-symbol-tables, $(dot-target).1s.o, $(dot-target).2s.o)
-       $(LD) $(call EFI_LDFLAGS,$(VIRT_BASE)) -T $(obj)/efi.lds $< 
$(obj)/efi/relocs-empty.o \
-             $(dot-target).2r.o $(dot-target).2s.o $(orphan-handling-y) \
-             $(note_file_option) -o $@
-       $(NM) -pa --format=sysv $@ \
-               | $(objtree)/tools/symbols --all-symbols --xensyms --sysv 
--sort \
-               > $@.map
+       $(NM) -pa --format=sysv $< \
+         | $(objtree)/tools/symbols --all-symbols --xensyms --sysv --sort \
+         > $@.map
 ifeq ($(CONFIG_DEBUG_INFO),y)
-       $(if $(filter --strip-debug,$(EFI_LDFLAGS)),:$(space))$(OBJCOPY) -O 
elf64-x86-64 $@ $@.elf
+       $(if $(filter --strip-debug,$(EFI_LDFLAGS)),:$(space))$(OBJCOPY) -O 
elf64-x86-64 $< $@.elf
 endif
+       $(final-image-check-y)
+       mv $< $@
        rm -f $(dot-target).[0-9]* $(@D)/..$(@F).[0-9]*
-ifeq ($(CONFIG_XEN_IBT),y)
-       $(SHELL) $(srctree)/tools/check-endbr.sh $@
-endif
 else
 $(TARGET).efi: FORCE
        rm -f $@
--- /dev/null
+++ b/xen/scripts/Makefile.link
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Helper rules for linking xen-syms
+# ==========================================================================
+
+syms-warn-dup-y := --warn-dup
+syms-warn-dup-$(CONFIG_SUPPRESS_DUPLICATE_SYMBOL_WARNINGS) :=
+syms-warn-dup-$(CONFIG_ENFORCE_UNIQUE_SYMBOLS) := --error-dup
+
+orphan-handling-$(call ld-option,--orphan-handling=warn) := 
--orphan-handling=warn
+
+final-image-check-y ?= true
+
+.INTERMEDIATE: $(addprefix .$(TARGET)-syms.,$(foreach n,0 1 2 3,$(n) $(n).o 
$(n).S))
+
+.$(TARGET)-syms.%.o: .$(TARGET)-syms.%.S
+       $(call cmd,cc_o_S)
+
+.$(TARGET)-syms.0.S:
+       $(objtree)/tools/symbols $(all_symbols) --empty > $@
+
+.$(TARGET)-syms.1.S: .$(TARGET)-syms.0
+.$(TARGET)-syms.2.S: .$(TARGET)-syms.1
+.$(TARGET)-syms.3.S: .$(TARGET)-syms.2
+
+.$(TARGET)-syms.%.S:
+       $(NM) -pa --format=sysv $< \
+         | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
+           $(if $(filter $(LAST_LINKING_PASS),$*), $(syms-warn-dup-y)) \
+         > $@
+
+.$(TARGET)-syms.%: $(objtree)/prelink.o .$(TARGET)-syms.%.o $(obj)/xen.lds
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $(filter %.o,$^) \
+             $(build_id_linker) --strip-debug -o $@
+
+.$(TARGET)-syms.$(LAST_LINKING_PASS): $(objtree)/prelink.o \
+                                      .$(TARGET)-syms.$(LAST_LINKING_PASS).o \
+                                      $(obj)/xen.lds
+       $(call compare-symbol-tables, \
+              .$(TARGET)-syms.$(shell expr $(LAST_LINKING_PASS) - 1).o, \
+              .$(TARGET)-syms.$(LAST_LINKING_PASS).o)
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $(filter %.o,$^) \
+             $(build_id_linker) $(orphan-handling-y) -o $@
+
+$(TARGET)-syms: .$(TARGET)-syms.$(LAST_LINKING_PASS)
+       $(NM) -pa --format=sysv $< \
+         | $(objtree)/tools/symbols --all-symbols --xensyms --sysv --sort \
+         > $@.map
+       $(final-image-check-y)
+       mv $< $@
+       rm -f $(dot-target).[0-9]* $(@D)/..$(@F).[0-9]*