Hi Masahiro, Michal,
While updating our systems from 4.9 to 5.4, we noticed that one of the
kernel modules that we build, which is done by linking an object that we
pre-compile out of Kbuild stopped working.
I bisected it down to:
commit 69ea912fda74a673d330d23595385e5b73e3a2b9 (refs/bisect/bad)
Author: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Date: Thu Oct 4 13:25:19 2018 +0900
kbuild: remove unneeded link_multi_deps
Since commit c8589d1e9e01 ("kbuild: handle multi-objs dependency
appropriately"), $^ really represents all the prerequisite of the
composite object being built.
Hence, $(filter %.o,$^) contains all the objects to link together,
which is much simpler than link_multi_deps calculation.
Please note $(filter-out FORCE,$^) does not work here. When a single
object module is turned into a multi object module, $^ will contain
header files that were previously included for building the single
object, and recorded in the .*.cmd file. To filter out such headers,
$(filter %.o,$^) should be used here.
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
and the linker now fails with the following:
mkdir -p /home/florian/dev/lkm/.tmp_versions ; rm -f
/home/florian/dev/lkm/.tmp_versions/*
WARNING: Symbol version dump ./Module.symvers
is missing; modules will have no dependencies and modversions.
make -f ./scripts/Makefile.build obj=/home/florian/dev/lkm
(cat /dev/null; echo kernel//home/florian/dev/lkm/hello.ko;) >
/home/florian/dev/lkm/modules.order
ld -m elf_x86_64 -z max-page-size=0x200000 -r -o
/home/florian/dev/lkm/hello.o
ld: no input files
make[1]: *** [scripts/Makefile.build:492: /home/florian/dev/lkm/hello.o]
Error 1
make: *** [Makefile:1530: _module_/home/florian/dev/lkm] Error 2
and here are some steps to reproduce this:
Kbuild:
obj-m := hello.o
hello-y := test.o_shipped
test.c can be a simple hello world, and you can compile it using a
standard Kbuild file first, and then move test.o as test.o_shipped.
I am afraid I do not speak Kbuild fluently enough to recommend a fix for
that.
Thanks!
--
Florian
