[xen staging] lib: collect library files in an archive

[patchbot@xxxxxxx]

commit f301f9a9e84f3cfd18750065f8a3794c8182c7f0
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Dec 18 13:17:57 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Dec 18 13:17:57 2020 +0100

    lib: collect library files in an archive
    
    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.
    
    Note further that --start-group / --end-group get put in place right
    away to allow for symbol resolution across all archives, once we gain
    multuiple ones.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Wei Liu <wl@xxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/Rules.mk          | 29 +++++++++++++++++++++++++----
 xen/arch/arm/Makefile |  6 +++---
 xen/arch/x86/Makefile |  8 ++++----
 xen/lib/Makefile      |  3 ++-
 4 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index d5e5eb33de..aba6ca2a90 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)
@@ -129,7 +144,7 @@ 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) $(extra-y)
 ifeq ($(strip $(obj-y)),)
        $(CC) $(c_flags) -c -x c /dev/null -o $@
 else
@@ -140,8 +155,14 @@ else
 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 ad2d497c45..512ffdd781 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 9b368632fb..8f2180485b 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 53b1da025e..b8814361d6 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
--
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