On Mon, Jan 20, 2025 at 11:30 AM Jinghao Jia <jinghao7@xxxxxxxxxxxx> wrote:
>
> Commit 13b25489b6f8 ("kbuild: change working directory to external
> module directory with M=") changed kbuild working directory of bpf
> samples to $(srctree)/samples/bpf, which broke the vmlinux path for
> VMLINUX_BTF, as the Makefile assumes the current work directory to be
> $(srctree):
>
> Makefile:316: *** Cannot find a vmlinux for VMLINUX_BTF at any of " /path/to/linux/samples/bpf/vmlinux", build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable. Stop.
>
> Correctly refer to the kernel source directory using $(srctree).
>
> Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
> Tested-by: Ruowen Qin <ruqin@xxxxxxxxxx>
> Signed-off-by: Jinghao Jia <jinghao7@xxxxxxxxxxxx>
> ---
> samples/bpf/Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 96a05e70ace3..f97295724a14 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -307,7 +307,7 @@ $(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check=
>
> VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux)) \
> $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)) \
> - $(abspath ./vmlinux)
> + $(abspath $(srctree)/vmlinux)
This is wrong and will not work for O= build.
The prefix should be $(objtree)/
> VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
>
> $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
> --
> 2.48.1
>
--
Best Regards
Masahiro Yamada
