netdev - Re: [PATCH bpf-next] bpf/preload: Clean up .gitignore and "clean-files" target

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Date:   Tue, 19 Oct 2021 16:50:07 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Quentin Monnet <quentin@...valent.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf/preload: Clean up .gitignore and
 "clean-files" target

On Sat, Oct 9, 2021 at 5:24 PM Quentin Monnet <quentin@...valent.com> wrote:
>
> kernel/bpf/preload/Makefile was recently updated to have it install
> libbpf's headers locally instead of pulling them from tools/lib/bpf. But
> two items still need to be addressed.
>
> First, the local .gitignore file was not adjusted to ignore the files
> generated in the new kernel/bpf/preload/libbpf output directory.
>
> Second, the "clean-files" target is now incorrect. The old artefacts
> names were not removed from the target, while the new ones were added
> incorrectly. This is because "clean-files" expects names relative to
> $(obj), but we passed the absolute path instead. This results in the
> output and header-destination directories for libbpf (and their
> contents) not being removed from kernel/bpf/preload on "make clean" from
> the root of the repository.
>
> This commit fixes both issues. Note that $(userprogs) needs not be added
> to "clean-files", because the cleaning infrastructure already accounts
> for it.
>
> Cleaning the files properly also prevents make from printing the
> following message, for builds coming after a "make clean":
> "make[4]: Nothing to be done for 'install_headers'."
>
> Fixes: bf60791741d4 ("bpf: preload: Install libbpf headers when building")
> Signed-off-by: Quentin Monnet <quentin@...valent.com>
> ---
>  kernel/bpf/preload/.gitignore | 4 +---
>  kernel/bpf/preload/Makefile   | 3 +--
>  2 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/bpf/preload/.gitignore b/kernel/bpf/preload/.gitignore
> index 856a4c5ad0dd..9452322902a5 100644
> --- a/kernel/bpf/preload/.gitignore
> +++ b/kernel/bpf/preload/.gitignore
> @@ -1,4 +1,2 @@
> -/FEATURE-DUMP.libbpf
> -/bpf_helper_defs.h
> -/feature
> +/libbpf
>  /bpf_preload_umd
> diff --git a/kernel/bpf/preload/Makefile b/kernel/bpf/preload/Makefile
> index 469d35e890eb..d8379af88161 100644
> --- a/kernel/bpf/preload/Makefile
> +++ b/kernel/bpf/preload/Makefile
> @@ -27,8 +27,7 @@ userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
>
>  userprogs := bpf_preload_umd
>
> -clean-files := $(userprogs) bpf_helper_defs.h FEATURE-DUMP.libbpf staticobjs/ feature/
> -clean-files += $(LIBBPF_OUT) $(LIBBPF_DESTDIR)
> +clean-files := $(subst $(abspath $(obj))/,,$(LIBBPF_OUT) $(LIBBPF_DESTDIR))

why so complicated? also isn't LIBBPF_OUT and LIBBPF_DESTDIR the same?
Wouldn't just this work and be super clear:

clean-files: libbpf/

?

>
>  $(obj)/iterators/iterators.o: | libbpf_hdrs
>
> --
> 2.30.2
>