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kbuild: do not create orphan built-in.a or obj-y objects 

Both 'obj-y += foo/' and 'obj-m += foo/' request Kbuild to visit the
sub-directory foo/, but the difference is that only the former combines
foo/built-in.a into the built-in.a of the current directory because
everything in sub-directories visited by obj-m is supposed to be modular.

So, it makes sense to create built-in.a only if that sub-directory is
reachable by the chain of obj-y. Otherwise, built-in.a will not be
linked into vmlinux anyway. For the same reason, it is pointless to
compile obj-y objects in the directory visited by obj-m.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2019-12-19 01:04:28 +09:00
parent 0186b1267b
commit 56d5893615
2 changed files with 5 additions and 1 deletions
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2
scripts/Makefile.build
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@ -66,7 +66,7 @@ lib-target := $(obj)/lib.a
real-obj-y += $(obj)/lib-ksyms.o
endif
ifneq ($(strip $(real-obj-y) $(need-builtin)),)
ifdef need-builtin
builtin-target := $(obj)/built-in.a
endif

4
scripts/Makefile.lib
View File

@ -35,7 +35,11 @@ __subdir-y := $(patsubst %/,%,$(filter %/, $(obj-y)))
subdir-y += $(__subdir-y)
__subdir-m := $(patsubst %/,%,$(filter %/, $(obj-m)))
subdir-m += $(__subdir-m)
ifdef need-builtin
obj-y := $(patsubst %/, %/built-in.a, $(obj-y))
else
obj-y := $(filter-out %/, $(obj-y))
endif
obj-m := $(filter-out %/, $(obj-m))
# Subdirectories we need to descend into