[PATCH v2 2/8] lib: collect library files in an archive

[Jan Beulich <jbeulich@xxxxxxxx>]

In order to (subsequently) drop odd things like CONFIG_NEEDS_LIST_SORT
just to avoid bloating binaries when only some arch-es and/or
configurations need generic library routines, combine objects under lib/
into an archive, which the linker then can pick the necessary objects
out of.

Note that we can't use thin archives just yet, until we've raised the
minimum required binutils version suitably.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/Rules.mk          | 33 +++++++++++++++++++++++++++------
 xen/arch/arm/Makefile |  6 +++---
 xen/arch/x86/Makefile |  8 ++++----
 xen/lib/Makefile      |  3 ++-
 4 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index 333e19bec343..e59c7f213f77 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -41,12 +41,16 @@ ALL_OBJS-y               += $(BASEDIR)/xsm/built_in.o
 ALL_OBJS-y               += $(BASEDIR)/arch/$(TARGET_ARCH)/built_in.o
 ALL_OBJS-$(CONFIG_CRYPTO)   += $(BASEDIR)/crypto/built_in.o
 
+ALL_LIBS-y               := $(BASEDIR)/lib/lib.a
+
 # Initialise some variables
+lib-y :=
 targets :=
 CFLAGS-y :=
 AFLAGS-y :=
 
 ALL_OBJS := $(ALL_OBJS-y)
+ALL_LIBS := $(ALL_LIBS-y)
 
 SPECIAL_DATA_SECTIONS := rodata $(foreach a,1 2 4 8 16, \
                                             $(foreach w,1 2 4, \
@@ -60,7 +64,14 @@ include Makefile
 # ---------------------------------------------------------------------------
 
 quiet_cmd_ld = LD      $@
-cmd_ld = $(LD) $(XEN_LDFLAGS) -r -o $@ $(real-prereqs)
+cmd_ld = $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out %.a,$(real-prereqs)) \
+               --start-group $(filter %.a,$(real-prereqs)) --end-group
+
+# Archive
+# ---------------------------------------------------------------------------
+
+quiet_cmd_ar = AR      $@
+cmd_ar = rm -f $@; $(AR) cPrs $@ $(real-prereqs)
 
 # Objcopy
 # ---------------------------------------------------------------------------
@@ -86,6 +97,10 @@ obj-y    := $(patsubst %/, %/built_in.o, $(obj-y))
 # tell kbuild to descend
 subdir-obj-y := $(filter %/built_in.o, $(obj-y))
 
+# Libraries are always collected in one lib file.
+# Filter out objects already built-in
+lib-y := $(filter-out $(obj-y), $(sort $(lib-y)))
+
 $(filter %.init.o,$(obj-y) $(obj-bin-y) $(extra-y)): CFLAGS-y += 
-DINIT_SECTIONS_ONLY
 
 ifeq ($(CONFIG_COVERAGE),y)
@@ -129,19 +144,25 @@ include $(BASEDIR)/arch/$(TARGET_ARCH)/Rules.mk
 c_flags += $(CFLAGS-y)
 a_flags += $(CFLAGS-y) $(AFLAGS-y)
 
-built_in.o: $(obj-y) $(extra-y)
+built_in.o: $(obj-y) $(if $(strip $(lib-y)),lib.a) $(extra-y)
 ifeq ($(obj-y),)
        $(CC) $(c_flags) -c -x c /dev/null -o $@
 else
 ifeq ($(CONFIG_LTO),y)
-       $(LD_LTO) -r -o $@ $(filter-out $(extra-y),$^)
+       $(LD_LTO) -r -o $@ $(filter-out lib.a $(extra-y),$^)
 else
-       $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out $(extra-y),$^)
+       $(LD) $(XEN_LDFLAGS) -r -o $@ $(filter-out lib.a $(extra-y),$^)
 endif
 endif
 
+lib.a: $(lib-y) FORCE
+       $(call if_changed,ar)
+
 targets += built_in.o
-targets += $(filter-out $(subdir-obj-y), $(obj-y)) $(extra-y)
+ifneq ($(strip $(lib-y)),)
+targets += lib.a
+endif
+targets += $(filter-out $(subdir-obj-y), $(obj-y) $(lib-y)) $(extra-y)
 targets += $(MAKECMDGOALS)
 
 built_in_bin.o: $(obj-bin-y) $(extra-y)
@@ -155,7 +176,7 @@ endif
 PHONY += FORCE
 FORCE:
 
-%/built_in.o: FORCE
+%/built_in.o %/lib.a: FORCE
        $(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o
 
 %/built_in_bin.o: FORCE
diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 296c5e68bbc3..612a83b315c8 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -90,14 +90,14 @@ endif
 
 ifeq ($(CONFIG_LTO),y)
 # Gather all LTO objects together
-prelink_lto.o: $(ALL_OBJS)
-       $(LD_LTO) -r -o $@ $^
+prelink_lto.o: $(ALL_OBJS) $(ALL_LIBS)
+       $(LD_LTO) -r -o $@ $(filter-out %.a,$^) --start-group $(filter %.a,$^) 
--end-group
 
 # Link it with all the binary objects
 prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
        $(call if_changed,ld)
 else
-prelink.o: $(ALL_OBJS) FORCE
+prelink.o: $(ALL_OBJS) $(ALL_LIBS) FORCE
        $(call if_changed,ld)
 endif
 
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 9b368632fb43..8f2180485b2b 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -132,8 +132,8 @@ 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_lto.o: $(ALL_OBJS) $(ALL_LIBS)
+       $(LD_LTO) -r -o $@ $(filter-out %.a,$^) --start-group $(filter %.a,$^) 
--end-group
 
 # Link it with all the binary objects
 prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o 
$(EFI_OBJS-y) FORCE
@@ -142,10 +142,10 @@ prelink.o: $(patsubst 
%/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o $
 prelink-efi.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) 
prelink_lto.o FORCE
        $(call if_changed,ld)
 else
-prelink.o: $(ALL_OBJS) $(EFI_OBJS-y) FORCE
+prelink.o: $(ALL_OBJS) $(ALL_LIBS) $(EFI_OBJS-y) FORCE
        $(call if_changed,ld)
 
-prelink-efi.o: $(ALL_OBJS) FORCE
+prelink-efi.o: $(ALL_OBJS) $(ALL_LIBS) FORCE
        $(call if_changed,ld)
 endif
 
diff --git a/xen/lib/Makefile b/xen/lib/Makefile
index 53b1da025e0d..b8814361d63e 100644
--- a/xen/lib/Makefile
+++ b/xen/lib/Makefile
@@ -1,2 +1,3 @@
-obj-y += ctype.o
 obj-$(CONFIG_X86) += x86/
+
+lib-y += ctype.o
-- 
2.22.0