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. ```

To resolve this, override the srctree in the kselftests's top Makefile 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.

Cc: Andrii Nakryiko andrii.nakryiko@gmail.com Signed-off-by: Li Zhijian lizhijian@fujitsu.com Tested-by: Quentin Monnet qmo@kernel.org --- Cc: Masahiro Yamada masahiroy@kernel.org

V3: collected Tested-by and rebased on bpf-next

V2: - handle srctree in selftests itself rather than the linux' top Makefile # Masahiro Yamada masahiroy@kernel.org

V1: https://lore.kernel.org/lkml/20241217031052.69744-1-lizhijian@fujitsu.com/ --- tools/testing/selftests/Makefile | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile index 2401e973c359..f04a3b0003f6 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -154,15 +154,19 @@ override LDFLAGS = override MAKEFLAGS = endif

+top_srcdir ?= ../../.. + # Append kselftest to KBUILD_OUTPUT and O to avoid cluttering # KBUILD_OUTPUT with selftest objects and headers installed # by selftests Makefile or lib.mk. +# Override the `srctree` variable to ensure it is correctly resolved in +# sub-Makefiles, such as those within `bpf`, when managing targets like +# `net` and `hid`. ifdef building_out_of_srctree override LDFLAGS = +override srctree := $(top_srcdir) endif

-top_srcdir ?= ../../.. - ifeq ("$(origin O)", "command line") KBUILD_OUTPUT := $(O) endif