linux-kernel - Re: [PATCH 2/2] makefiles: do not generate empty vmlinux.h

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Message-ID: <CAEf4BzZ6Ks0T=72vtGNc0TyPxHMO6PEFQb8TEYj7XmtqWjfDwQ@mail.gmail.com>
Date:   Mon, 28 Nov 2022 22:00:14 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Changbin Du <changbin.du@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mykola Lysenko <mykolal@...com>,
        linux-perf-users@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/2] makefiles: do not generate empty vmlinux.h

On Sat, Nov 26, 2022 at 3:13 AM Changbin Du <changbin.du@...il.com> wrote:
>
> Remove the empty vmlinux.h if bpftool failed to dump btf info.
> The emptry vmlinux.h can hide real error when reading output
> of make.

wouldn't this be better handled by adding .DELETE_ON_ERROR: to
bpftool's Makefile?

>
> Signed-off-by: Changbin Du <changbin.du@...il.com>
> ---
>  samples/bpf/Makefile                 | 2 +-
>  tools/bpf/bpftool/Makefile           | 2 +-
>  tools/bpf/runqslower/Makefile        | 2 +-
>  tools/perf/Makefile.perf             | 2 +-
>  tools/testing/selftests/bpf/Makefile | 2 +-
>  5 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 727da3c5879b..ab4788b4883e 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -362,7 +362,7 @@ ifeq ($(VMLINUX_BTF),)
>         $(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\
>                 build the kernel or set VMLINUX_BTF or VMLINUX_H variable)
>  endif
> -       $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
> +       $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@ || { rm $@; exit 1; }
>  else
>         $(Q)cp "$(VMLINUX_H)" $@
>  endif
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 4a95c017ad4c..d9d6f890884c 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -177,7 +177,7 @@ BUILD_BPF_SKELS := 1
>
>  $(OUTPUT)vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL_BOOTSTRAP)
>  ifeq ($(VMLINUX_H),)
> -       $(QUIET_GEN)$(BPFTOOL_BOOTSTRAP) btf dump file $< format c > $@
> +       $(QUIET_GEN)$(BPFTOOL_BOOTSTRAP) btf dump file $< format c > $@ || { rm $@; exit 1; }
>  else
>         $(Q)cp "$(VMLINUX_H)" $@
>  endif
> diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
> index 8b3d87b82b7a..2d7911f4666b 100644
> --- a/tools/bpf/runqslower/Makefile
> +++ b/tools/bpf/runqslower/Makefile
> @@ -77,7 +77,7 @@ ifeq ($(VMLINUX_H),)
>                         "specify its location." >&2;                           \
>                 exit 1;\
>         fi
> -       $(QUIET_GEN)$(BPFTOOL) btf dump file $(VMLINUX_BTF_PATH) format c > $@
> +       $(QUIET_GEN)$(BPFTOOL) btf dump file $(VMLINUX_BTF_PATH) format c > $@ || { rm $@; exit 1; }
>  else
>         $(Q)cp "$(VMLINUX_H)" $@
>  endif
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index a432e59afc42..0546d408aa4e 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -1064,7 +1064,7 @@ VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
>
>  $(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
>  ifeq ($(VMLINUX_H),)
> -       $(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@
> +       $(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@ || { rm $@; exit 1; }
>  else
>         $(Q)cp "$(VMLINUX_H)" $@
>  endif
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index e6cf21fad69f..9aa2475b4ac6 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -284,7 +284,7 @@ endif
>  $(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL) | $(INCLUDE_DIR)
>  ifeq ($(VMLINUX_H),)
>         $(call msg,GEN,,$@)
> -       $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
> +       $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@ || { rm $@; exit 1; }
>  else
>         $(call msg,CP,,$@)
>         $(Q)cp "$(VMLINUX_H)" $@
> --
> 2.37.2
>