Re: [bpf-next PATCH v2 3/4] kbuild: skip module BTF with one-time check for vmlinux

Jiri Olsa
2023-10-19T08:17:36Z

On Thu, Oct 19, 2023 at 12:19:49AM +0900, Masahiro Yamada wrote:
> When CONFIG_DEBUG_INFO_BTF_MODULES is enabled, vmlinux presence is
> checked in every module build, resulting in repetitive warning
> messages if vmlinux is missing.
>
> Check vmlinux and print a warning just once.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nicolas Schier <n.schier@avm.de>

lgtm

Acked-by: Jiri Olsa <jolsa@kernel.org>

jirka

> ---
>
> (no changes since v1)
>
> scripts/Makefile.modfinal | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 8568d256d6fb..9fd7a26e4fe9 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -14,6 +14,15 @@ include $(srctree)/scripts/Makefile.lib
>
> # find all modules listed in modules.order
> modules := $(call read-file, $(MODORDER))
> +vmlinux :=
> +
> +ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> +ifneq ($(wildcard vmlinux),)
> +vmlinux := vmlinux
> +else
> +$(warning Skipping BTF generation due to unavailability of vmlinux)
> +endif
> +endif
>
> __modfinal: $(modules:%.o=%.ko)
> @:
> @@ -36,12 +45,8 @@ quiet_cmd_ld_ko_o = LD [M] $@
>
> quiet_cmd_btf_ko = BTF [M] $@
> cmd_btf_ko = \
> - if [ ! -f vmlinux ]; then \
> - printf "Skipping BTF generation for %s due to unavailability of vmlinux\n" $@ 1>&2; \
> - else \
> LLVM_OBJCOPY="$(OBJCOPY)" $(PAHOLE) -J $(PAHOLE_FLAGS) --btf_base vmlinux $@; \
> - $(RESOLVE_BTFIDS) -b vmlinux $@; \
> - fi;
> + $(RESOLVE_BTFIDS) -b vmlinux $@
>
> # Same as newer-prereqs, but allows to exclude specified extra dependencies
> newer_prereqs_except = $(filter-out $(PHONY) $(1),$?)
> @@ -52,9 +57,9 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check), \
> printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
>
> # Re-generate module BTFs if either module's .ko or vmlinux changed
> -%.ko: %.o %.mod.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
> +%.ko: %.o %.mod.o scripts/module.lds $(vmlinux) FORCE
> +$(call if_changed_except,ld_ko_o,vmlinux)
> -ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> +ifdef vmlinux
> +$(if $(newer-prereqs),$(call cmd,btf_ko))
> endif
>
> --
> 2.40.1
>
>