2024-12-17 11:10 UTC+0800 ~ Li Zhijian lizhijian@fujitsu.com
Fixes an issue where out-of-tree kselftest builds fail when building the BPF and bpftools components. The failure occurs because the top-level Makefile passes a relative srctree path ('..') to its sub-Makefiles, which leads to errors in locating necessary files.
For example, the following error is encountered:
$ make V=1 O=$build/ TARGETS=hid kselftest-all ... make -C ../tools/testing/selftests all make[4]: Entering directory '/path/to/linux/tools/testing/selftests/hid' make -C /path/to/linux/tools/testing/selftests/../../../tools/lib/bpf OUTPUT=/path/to/linux/O/kselftest/hid/tools/build/libbpf/ \ EXTRA_CFLAGS='-g -O0' \ DESTDIR=/path/to/linux/O/kselftest/hid/tools prefix= all install_headers make[5]: Entering directory '/path/to/linux/tools/lib/bpf' ... make[5]: Entering directory '/path/to/linux/tools/bpf/bpftool' Makefile:127: ../tools/build/Makefile.feature: No such file or directory make[5]: *** No rule to make target '../tools/build/Makefile.feature'. Stop.
Another condition to reproduce the failure above is to have have $(srcroot) in the Makefile set to "." or "..", for example when your $build is located right under the root of the repo [0].
[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Make...
To resolve this, the srctree is exported as an absolute path (abs_srctree) when performing an out-of-tree build. This ensures that all sub-Makefiles have the correct path to the source tree, preventing directory resolution errors.
Signed-off-by: Li Zhijian lizhijian@fujitsu.com
Request for Additional Testing
We welcome all contributors and CI systems to test this change thoroughly. In theory, this change should not affect in-tree builds. However, to ensure stability and compatibility, we encourage testing across different configurations.
What has been tested?
- out-of-tree kernel build
- out-of-tree kselftest-all
Makefile | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile index e5b8a8832c0c..36e65806bb5e 100644 --- a/Makefile +++ b/Makefile @@ -275,7 +275,8 @@ else ifeq ($(srcroot)/,$(dir $(CURDIR))) srcroot := .. endif -export srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot)) +srctree := $(if $(KBUILD_EXTMOD),$(abs_srctree),$(srcroot)) +export srctree := $(if $(building_out_of_srctree),$(abs_srctree),$(srctree)) ifdef building_out_of_srctree export VPATH := $(srcroot)
The patch does fix the issue in the case you reported.
Maybe I'd write the change differently, though; rather than potentially overwriting $(srctree) before exporting it, let's unroll with ifdef's to make it clearer?
ifdef building_out_of_srctree srctree := $(abs_srctree) else ifdef KBUILD_EXTMOD srctree := $(abs_srctree) else srctree := $(srcroot) endif export srctree
(not tested)
Thanks, Quentin