linux-kernel - Re: [PATCH v2] bpf: Remove custom build rule

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Message-ID: <Zs9jPsBY_SNuuB3d@example.org>
Date: Wed, 28 Aug 2024 19:49:50 +0200
From: Alexey Gladkov <gladkov.alexey@...il.com>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	linux-kbuild@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v2] bpf: Remove custom build rule

On Thu, Aug 29, 2024 at 02:22:33AM +0900, Masahiro Yamada wrote:
> On Thu, Aug 29, 2024 at 2:07 AM Alexey Gladkov <legion@...nel.org> wrote:
> >
> > According to the documentation, when building a kernel with the C=2
> > parameter, all source files should be checked. But this does not happen
> > for the kernel/bpf/ directory.
> >
> > $ touch kernel/bpf/core.o
> > $ make C=2 CHECK=true kernel/bpf/core.o
> >
> > Outputs:
> >
> >   CHECK   scripts/mod/empty.c
> >   CALL    scripts/checksyscalls.sh
> >   DESCEND objtool
> >   INSTALL libsubcmd_headers
> >   CC      kernel/bpf/core.o
> >
> > As can be seen the compilation is done, but CHECK is not executed. This
> > happens because kernel/bpf/Makefile has defined its own rule for
> > compilation and forgotten the macro that does the check.
> >
> > There is no need to duplicate the build code, and this rule can be
> > removed to use generic rules.
> >
> > Signed-off-by: Alexey Gladkov <legion@...nel.org>
> 
> 
> Did you compile-test this?

Yes. I repeated my steps for reproduce:

$ touch kernel/bpf/core.c
$ make C=2 CHECK=true |grep kernel/bpf/core
  CC      kernel/bpf/core.o
  CHECK   kernel/bpf/core.c

but maybe my config is too small.

> 
> See my previous email.
> 
> 
> 
> 
> I said this:
> 
> $ cat kernel/bpf/btf_iter.c
> #include "../../tools/lib/bpf/btf_iter.c"
> 
> 
> Same for
> kernel/bpf/btf_relocate.c
> kernel/bpf/relo_core.c
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> > ---
> >  kernel/bpf/Makefile | 6 ------
> >  1 file changed, 6 deletions(-)
> >
> > diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
> > index 0291eef9ce92..9b9c151b5c82 100644
> > --- a/kernel/bpf/Makefile
> > +++ b/kernel/bpf/Makefile
> > @@ -52,9 +52,3 @@ obj-$(CONFIG_BPF_PRELOAD) += preload/
> >  obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
> >  obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o
> >  obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o
> > -
> > -# Some source files are common to libbpf.
> > -vpath %.c $(srctree)/kernel/bpf:$(srctree)/tools/lib/bpf
> > -
> > -$(obj)/%.o: %.c FORCE
> > -       $(call if_changed_rule,cc_o_c)
> > --
> > 2.46.0
> >
> 
> 
> --
> Best Regards
> Masahiro Yamada
> 

-- 
Rgrds, legion