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From: David Ahern <dsahern@gmail.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH v3 bpf-next 5/7] libbpf: move bpf_{helpers,endian,tracing}.h into libbpf
Date: Fri, 4 Oct 2019 09:44:44 -0600	[thread overview]
Message-ID: <4fcbe7bf-201a-727a-a6f1-2088aea82a33@gmail.com> (raw)
In-Reply-To: <CAEf4BzYRJ4i05prEJF_aCQK5jnmpSUqrwTXYsj4FDahCWcNQdQ@mail.gmail.com>

On 10/4/19 9:27 AM, Andrii Nakryiko wrote:
> On Fri, Oct 4, 2019 at 7:47 AM David Ahern <dsahern@gmail.com> wrote:
>>
>> On 10/3/19 3:28 PM, Andrii Nakryiko wrote:
>>> Move bpf_helpers.h, bpf_tracing.h, and bpf_endian.h into libbpf. Ensure
>>> they are installed along the other libbpf headers. Also, adjust
>>> selftests and samples include path to include libbpf now.
>>
>> There are side effects to bringing bpf_helpers.h into libbpf if this
>> gets propagated to the github sync.
>>
>> bpf_helpers.h references BPF_FUNC_* which are defined in the
>> uapi/linux/bpf.h header. That is a kernel version dependent api file
>> which means attempts to use newer libbpf with older kernel headers is
>> going to throw errors when compiling bpf programs -- bpf_helpers.h will
>> contain undefined BPF_FUNC references.
> 
> That's true, but I'm wondering if maintaining a copy of that enum in
> bpf_helpers.h itself is a good answer here?
> 
> bpf_helpers.h will be most probably used with BPF CO-RE and
> auto-generated vmlinux.h with all the enums and types. In that case,
> you'll probably want to use vmlinux.h for one of the latest kernels
> anyways.

I'm not following you; my interpretation of your comment seems like you
are making huge assumptions.

I build bpf programs for specific kernel versions using the devel
packages for the specific kernel of interest.

> 
> Nevertheless, it is a problem and thanks for bringing it up! I'd say
> for now we should still go ahead with this move and try to solve with
> issue once bpf_helpers.h is in libbpf. If bpf_helpers.h doesn't work
> for someone, it's no worse than it is today when users don't have
> bpf_helpers.h at all.
> 

If this syncs to the github libbpf, it will be worse than today in the
sense of compile failures if someone's header file ordering picks
libbpf's bpf_helpers.h over whatever they are using today.

  reply	other threads:[~2019-10-04 15:44 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-03 21:28 [PATCH v3 bpf-next 0/7] Move bpf_helpers and add BPF_CORE_READ macros Andrii Nakryiko
2019-10-03 21:28 ` [PATCH v3 bpf-next 1/7] selftests/bpf: undo GCC-specific bpf_helpers.h changes Andrii Nakryiko
2019-10-04  7:00   ` Toke Høiland-Jørgensen
2019-10-03 21:28 ` [PATCH v3 bpf-next 2/7] selftests/bpf: samples/bpf: split off legacy stuff from bpf_helpers.h Andrii Nakryiko
2019-10-04  7:00   ` Toke Høiland-Jørgensen
2019-10-03 21:28 ` [PATCH v3 bpf-next 3/7] selftests/bpf: adjust CO-RE reloc tests for new bpf_core_read() macro Andrii Nakryiko
2019-10-03 21:28 ` [PATCH v3 bpf-next 4/7] selftests/bpf: split off tracing-only helpers into bpf_tracing.h Andrii Nakryiko
2019-10-04  7:01   ` Toke Høiland-Jørgensen
2019-10-03 21:28 ` [PATCH v3 bpf-next 5/7] libbpf: move bpf_{helpers,endian,tracing}.h into libbpf Andrii Nakryiko
2019-10-04  7:01   ` Toke Høiland-Jørgensen
2019-10-04 14:47   ` David Ahern
2019-10-04 15:27     ` Andrii Nakryiko
2019-10-04 15:44       ` David Ahern [this message]
2019-10-04 16:00         ` Andrii Nakryiko
2019-10-04 18:30           ` Jakub Kicinski
2019-10-04 18:37             ` Yonghong Song
2019-10-04 21:04               ` Jakub Kicinski
2019-10-08 15:37               ` Jiri Benc
2019-10-08 18:02                 ` Andrii Nakryiko
2019-10-04 20:21             ` Andrii Nakryiko
2019-10-04 21:06               ` Daniel Borkmann
2019-10-04 21:58                 ` Daniel Borkmann
2019-10-04 22:47                   ` Andrii Nakryiko
2019-10-04 22:51                     ` Andrii Nakryiko
2019-10-04 23:25                       ` Andrii Nakryiko
2019-10-08 15:29             ` Jiri Benc
2019-10-03 21:28 ` [PATCH v3 bpf-next 6/7] libbpf: add BPF_CORE_READ/BPF_CORE_READ_INTO helpers Andrii Nakryiko
2019-10-03 21:28 ` [PATCH v3 bpf-next 7/7] selftests/bpf: add BPF_CORE_READ and BPF_CORE_READ_STR_INTO macro tests Andrii Nakryiko

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