[bpf-next] tools, bpftool: Correctly evaluate $(BUILD_BPF_SKELS) in Makefile

Currently, if the clang-bpf-co-re feature is not available, the build
fails with e.g.

  CC       prog.o
prog.c:1462:10: fatal error: profiler.skel.h: No such file or directory
 1462 | #include "profiler.skel.h"
      |          ^~~~~~~~~~~~~~~~~

This is due to the fact that the BPFTOOL_WITHOUT_SKELETONS macro is not
defined, despite BUILD_BPF_SKELS not being set. Fix this by correctly
evaluating $(BUILD_BPF_SKELS) when deciding on whether to add
-DBPFTOOL_WITHOUT_SKELETONS to CFLAGS.

Fixes: 05aca6da3b5a ("tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h")
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
---
 tools/bpf/bpftool/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

2020-06-23 12:37 UTC+0200 ~ Tobias Klauser <tklauser@distanz.ch>
> Currently, if the clang-bpf-co-re feature is not available, the build
> fails with e.g.
> 
>   CC       prog.o
> prog.c:1462:10: fatal error: profiler.skel.h: No such file or directory
>  1462 | #include "profiler.skel.h"
>       |          ^~~~~~~~~~~~~~~~~
> 
> This is due to the fact that the BPFTOOL_WITHOUT_SKELETONS macro is not
> defined, despite BUILD_BPF_SKELS not being set. Fix this by correctly
> evaluating $(BUILD_BPF_SKELS) when deciding on whether to add
> -DBPFTOOL_WITHOUT_SKELETONS to CFLAGS.
> 
> Fixes: 05aca6da3b5a ("tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h")
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Reviewed-by: Quentin Monnet <quentin@isovalent.com>

Thanks Tobias.

On Tue, Jun 23, 2020 at 3:37 AM Tobias Klauser <tklauser@distanz.ch> wrote:
>
> Currently, if the clang-bpf-co-re feature is not available, the build
> fails with e.g.
>
>   CC       prog.o
> prog.c:1462:10: fatal error: profiler.skel.h: No such file or directory
>  1462 | #include "profiler.skel.h"
>       |          ^~~~~~~~~~~~~~~~~
>
> This is due to the fact that the BPFTOOL_WITHOUT_SKELETONS macro is not
> defined, despite BUILD_BPF_SKELS not being set. Fix this by correctly
> evaluating $(BUILD_BPF_SKELS) when deciding on whether to add
> -DBPFTOOL_WITHOUT_SKELETONS to CFLAGS.
>
> Fixes: 05aca6da3b5a ("tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h")
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
>  tools/bpf/bpftool/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 06f436e8191a..8c6563e56ffc 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -155,7 +155,7 @@ $(OUTPUT)pids.o: $(OUTPUT)pid_iter.skel.h
>  endif
>  endif
>
> -CFLAGS += $(if BUILD_BPF_SKELS,,-DBPFTOOL_WITHOUT_SKELETONS)
> +CFLAGS += $(if $(BUILD_BPF_SKELS),,-DBPFTOOL_WITHOUT_SKELETONS)

Oh, what a rookie mistake :) Thanks for fixing!

Acked-by: Andrii Nakryiko <andriin@fb.com>

>
>  $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
>         $(QUIET_CC)$(CC) $(CFLAGS) -c -MMD -o $@ $<
> --
> 2.27.0
>

On 6/23/20 12:37 PM, Tobias Klauser wrote:
> Currently, if the clang-bpf-co-re feature is not available, the build
> fails with e.g.
> 
>    CC       prog.o
> prog.c:1462:10: fatal error: profiler.skel.h: No such file or directory
>   1462 | #include "profiler.skel.h"
>        |          ^~~~~~~~~~~~~~~~~
> 
> This is due to the fact that the BPFTOOL_WITHOUT_SKELETONS macro is not
> defined, despite BUILD_BPF_SKELS not being set. Fix this by correctly
> evaluating $(BUILD_BPF_SKELS) when deciding on whether to add
> -DBPFTOOL_WITHOUT_SKELETONS to CFLAGS.
> 
> Fixes: 05aca6da3b5a ("tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h")
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

Applied, thanks!