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>

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index b734ac8a654ecd8a6151e82b4f0817b7e79fcb96..e46b4ee9a120088374a23200dc3889499bada2e0 100644 (file)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -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
 

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3fa32f83b2d74c05a71ebb2fdc0a426471637875..724aa3e9b4a84d671aa75ebae6240e921e7d3cc0 100644 (file)
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -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