[xen staging-4.14] build: use if_changed more consistently (and correctly) for prelink*.o

[patchbot@xxxxxxx]

commit 9f954ae7fb1c7dc3b02e5ccac6978c3a8e86086e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Nov 4 11:01:02 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Nov 4 11:01:02 2020 +0100

    build: use if_changed more consistently (and correctly) for prelink*.o
    
    Switch to $(call if_changed,ld) where possible; presumably not doing so
    in e321576f4047 ("xen/build: start using if_changed") right away was an
    oversight, as it did for Arm in (just) one case. It failed to add
    prelink.o to $(targets), though, causing - judging from the observed
    behavior on x86 - undue rebuilds of the final binary (because of
    prelink.o getting rebuild for $(cmd_prelink.o) being empty, in turn
    because of .prelink.o.cmd not getting read) during "make install-xen".
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
    master commit: dd2cfba88c3d0e144ffec07c6b5b86e54a9d98a9
    master date: 2020-09-22 10:19:38 +0200
---
 xen/arch/arm/Makefile |  4 +++-
 xen/arch/x86/Makefile | 18 ++++++++++--------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
index 7e82b2178c..1ded44d200 100644
--- a/xen/arch/arm/Makefile
+++ b/xen/arch/arm/Makefile
@@ -95,12 +95,14 @@ 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) $(XEN_LDFLAGS) -r -o $@ $^
+       $(call if_changed,ld)
 else
 prelink.o: $(ALL_OBJS) FORCE
        $(call if_changed,ld)
 endif
 
+targets += prelink.o
+
 $(TARGET)-syms: prelink.o xen.lds
        $(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o \
            $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index b388861679..26ff2a9a3e 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -124,19 +124,21 @@ prelink-efi_lto.o: $(ALL_OBJS) efi/runtime.o efi/compat.o
        $(LD_LTO) -r -o $@ $(filter-out %/efi/built_in.o,$^)
 
 # Link it with all the binary objects
-prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
-       $(LD) $(XEN_LDFLAGS) -r -o $@ $^
+prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o 
FORCE
+       $(call if_changed,ld)
 
-prelink-efi.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) 
prelink-efi_lto.o efi/boot.init.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 FORCE
+       $(call if_changed,ld)
 else
-prelink.o: $(ALL_OBJS)
-       $(LD) $(XEN_LDFLAGS) -r -o $@ $^
+prelink.o: $(ALL_OBJS) FORCE
+       $(call if_changed,ld)
 
-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: $(filter-out %/efi/built_in.o,$(ALL_OBJS)) efi/boot.init.o 
efi/runtime.o efi/compat.o FORCE
+       $(call if_changed,ld)
 endif
 
+targets += prelink.o prelink-efi.o
+
 $(TARGET)-syms: prelink.o xen.lds
        $(LD) $(XEN_LDFLAGS) -T xen.lds -N prelink.o $(build_id_linker) \
            $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
--
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