[PATCH 1/1] kbuild: recursive build of external kernel modules

[Shaun Tancheff]

When building a tree of external modules stage 2 fails
silently as the root modules.order is empty.

Modify the modules.order location to be fixed to the
root when KBUILD_EXTMOD is specified and write all
module paths to the single modules.order file.

Signed-off-by: Shaun Tancheff <stancheff@xxxxxxxx>
---
 Makefile               | 1 +
 scripts/Makefile.build | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 23cdf1f41364..a9964492f47e 100644
--- a/Makefile
+++ b/Makefile
@@ -1622,6 +1622,7 @@ $(module-dirs): prepare $(objtree)/Module.symvers
 
 modules: $(module-dirs)
 	@$(kecho) '  Building modules, stage 2.';
+	$(Q)$rm -f $(KBUILD_EXTMOD)/modules.order
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
 PHONY += modules_install
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 0d434d0afc0b..f9908b3d59e0 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -64,7 +64,13 @@ builtin-target := $(obj)/built-in.a
 endif
 
 ifeq ($(CONFIG_MODULES)$(need-modorder),y1)
+ifneq ($(KBUILD_EXTMOD),)
+modorder-target := $(KBUILD_EXTMOD)/modules.order
+modorder-add := >>
+else
 modorder-target := $(obj)/modules.order
+modorder-add := >
+endif
 endif
 
 mod-targets := $(patsubst %.o, %.mod, $(obj-m))
@@ -423,7 +429,7 @@ endif # builtin-target
 $(modorder-target): $(subdir-ym) FORCE
 	$(Q){ $(foreach m, $(modorder), \
 	$(if $(filter %/modules.order, $m), cat $m, echo $m);) :; } \
-	| $(AWK) '!x[$$0]++' - > $@
+	| $(AWK) '!x[$$0]++' - $(modorder-add) $@
 
 #
 # Rule to compile a set of .o files into one .a file (with symbol table)
-- 
2.20.1