linux-kernel - Re: [bpf-next PATCH v2 4/4] kbuild: refactor module BTF rule

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Message-ID: <CAEf4BzZm4h4q6k9ZhuT5qiWC9PYA+c7XwVFd68iAq4mtMJ-qhw@mail.gmail.com>
Date:   Thu, 19 Oct 2023 15:54:52 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <olsajiri@...il.com>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>, bpf@...r.kernel.org
Subject: Re: [bpf-next PATCH v2 4/4] kbuild: refactor module BTF rule

On Thu, Oct 19, 2023 at 1:15 AM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Thu, Oct 19, 2023 at 12:19:50AM +0900, Masahiro Yamada wrote:
> > newer_prereqs_except and if_changed_except are ugly hacks of the
> > newer-prereqs and if_changed in scripts/Kbuild.include.
> >
> > Remove.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
> >
> > Changes in v2:
> >   - Fix if_changed_except to if_changed
> >
> >  scripts/Makefile.modfinal | 25 ++++++-------------------
> >  1 file changed, 6 insertions(+), 19 deletions(-)
> >
> > diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> > index 9fd7a26e4fe9..fc07854bb7b9 100644
> > --- a/scripts/Makefile.modfinal
> > +++ b/scripts/Makefile.modfinal
> > @@ -19,6 +19,9 @@ vmlinux :=
> >  ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> >  ifneq ($(wildcard vmlinux),)
> >  vmlinux := vmlinux
> > +cmd_btf = ; \
> > +     LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base vmlinux $@; \
> > +     $(RESOLVE_BTFIDS) -b vmlinux $@
> >  else
> >  $(warning Skipping BTF generation due to unavailability of vmlinux)
> >  endif
> > @@ -41,27 +44,11 @@ quiet_cmd_ld_ko_o = LD [M]  $@
> >        cmd_ld_ko_o +=                                                 \
> >       $(LD) -r $(KBUILD_LDFLAGS)                                      \
> >               $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)              \
> > -             -T scripts/module.lds -o $@ $(filter %.o, $^)
> > +             -T scripts/module.lds -o $@ $(filter %.o, $^)           \
> > +     $(cmd_btf)
> >
> > -quiet_cmd_btf_ko = BTF [M] $@
>
> nit not sure it's intentional but we no longer display 'BTF [M] ...ko' lines,
> I don't mind not displaying that, but we should mention that in changelog
>

Thanks for spotting this! I think those messages are useful and
important to keep. Masahiro, is it possible to preserve them?


> jirka
>
> > -      cmd_btf_ko =                                                   \
> > -             LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base vmlinux $@; \
> > -             $(RESOLVE_BTFIDS) -b vmlinux $@
> > -
> > -# Same as newer-prereqs, but allows to exclude specified extra dependencies
> > -newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
> > -
> > -# Same as if_changed, but allows to exclude specified extra dependencies
> > -if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
> > -     $(cmd);                                                              \
> > -     printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
> > -
> > -# Re-generate module BTFs if either module's .ko or vmlinux changed
> >  %.ko: %.o %.mod.o scripts/module.lds $(vmlinux) FORCE
> > -     +$(call if_changed_except,ld_ko_o,vmlinux)
> > -ifdef vmlinux
> > -     +$(if $(newer-prereqs),$(call cmd,btf_ko))
> > -endif
> > +     +$(call if_changed,ld_ko_o)
> >
> >  targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o)
> >
> > --
> > 2.40.1
> >
> >
>