Re: [PATCH bpf-next v2] bpftool: use linux/types.h from source tree for profiler build

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Tobias Klauser <tklauser@distanz.ch>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	bpf <bpf@vger.kernel.org>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Quentin Monnet <quentin@isovalent.com>
Subject: Re: [PATCH bpf-next v2] bpftool: use linux/types.h from source tree for profiler build
Date: Thu, 12 Mar 2020 10:59:55 -0700	[thread overview]
Message-ID: <CAEf4BzakzbN4+PVa4TFsOhH=Pnt_4mhPknH74kwsRkOApkKhOg@mail.gmail.com> (raw)
In-Reply-To: <20200312130330.32239-1-tklauser@distanz.ch>

On Thu, Mar 12, 2020 at 6:04 AM Tobias Klauser <tklauser@distanz.ch> wrote:
>
> When compiling bpftool on a system where the /usr/include/asm symlink
> doesn't exist (e.g. on an Ubuntu system without gcc-multilib installed),
> the build fails with:
>
>     CLANG    skeleton/profiler.bpf.o
>   In file included from skeleton/profiler.bpf.c:4:
>   In file included from /usr/include/linux/bpf.h:11:
>   /usr/include/linux/types.h:5:10: fatal error: 'asm/types.h' file not found
>   #include <asm/types.h>
>            ^~~~~~~~~~~~~
>   1 error generated.
>   make: *** [Makefile:123: skeleton/profiler.bpf.o] Error 1
>
> This indicates that the build is using linux/types.h from system headers
> instead of source tree headers.
>
> To fix this, adjust the clang search path to include the necessary
> headers from tools/testing/selftests/bpf/include/uapi and
> tools/include/uapi. Also use __bitwise__ instead of __bitwise in
> skeleton/profiler.h to avoid clashing with the definition in
> tools/testing/selftests/bpf/include/uapi/linux/types.h.
>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Song Liu <songliubraving@fb.com>
> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> Cc: Quentin Monnet <quentin@isovalent.com>
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> ---
>  tools/bpf/bpftool/Makefile            |  5 ++++-
>  tools/bpf/bpftool/skeleton/profiler.h | 17 ++++++++---------
>  2 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 20a90d8450f8..f294f6c1e795 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -120,7 +120,10 @@ $(OUTPUT)_bpftool: $(_OBJS) $(LIBBPF)
>         $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(_OBJS) $(LIBS)
>
>  skeleton/profiler.bpf.o: skeleton/profiler.bpf.c
> -       $(QUIET_CLANG)$(CLANG) -I$(srctree)/tools/lib -g -O2 -target bpf -c $< -o $@
> +       $(QUIET_CLANG)$(CLANG) \
> +               -I$(srctree)/tools/include/uapi/ \
> +               -I$(srctree)/tools/testing/selftests/bpf/include/uapi \

Seems like I'm spoiling all the fun today :) But why are we ok with
bpftool build depending on selftests? This just makes it even harder
to have a stand-alone bpftool build eventually (similar to libbpf's
Github).

> +               -I$(srctree)/tools/lib -g -O2 -target bpf -c $< -o $@
>
>  profiler.skel.h: $(OUTPUT)_bpftool skeleton/profiler.bpf.o
>         $(QUIET_GEN)$(OUTPUT)./_bpftool gen skeleton skeleton/profiler.bpf.o > $@
> diff --git a/tools/bpf/bpftool/skeleton/profiler.h b/tools/bpf/bpftool/skeleton/profiler.h
> index e03b53eae767..1f767e9510f7 100644
> --- a/tools/bpf/bpftool/skeleton/profiler.h
> +++ b/tools/bpf/bpftool/skeleton/profiler.h
> @@ -32,16 +32,15 @@ enum {
>  #else
>  #define __bitwise__
>  #endif
> -#define __bitwise __bitwise__
>
> -typedef __u16 __bitwise __le16;
> -typedef __u16 __bitwise __be16;
> -typedef __u32 __bitwise __le32;
> -typedef __u32 __bitwise __be32;
> -typedef __u64 __bitwise __le64;
> -typedef __u64 __bitwise __be64;
> +typedef __u16 __bitwise__ __le16;
> +typedef __u16 __bitwise__ __be16;
> +typedef __u32 __bitwise__ __le32;
> +typedef __u32 __bitwise__ __be32;
> +typedef __u64 __bitwise__ __le64;
> +typedef __u64 __bitwise__ __be64;
>
> -typedef __u16 __bitwise __sum16;
> -typedef __u32 __bitwise __wsum;
> +typedef __u16 __bitwise__ __sum16;
> +typedef __u32 __bitwise__ __wsum;
>
>  #endif /* __PROFILER_H */
> --
> 2.25.1
>