Re: [PATCH bpf v2 1/1] lib: bpf: tracing: fail compilation if target arch is missing

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Lorenz Bauer <lmb@cloudflare.com>
Cc: Andrii Nakryiko <andrii@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
	kernel-team <kernel-team@cloudflare.com>
Subject: Re: [PATCH bpf v2 1/1] lib: bpf: tracing: fail compilation if target arch is missing
Date: Wed, 16 Jun 2021 21:24:39 -0700	[thread overview]
Message-ID: <CAEf4BzbJRMuG_h9x1mv_ab_JHA-gx6=+6bc9ydAWPNGV_jQpOA@mail.gmail.com> (raw)
In-Reply-To: <20210616083635.11434-1-lmb@cloudflare.com>

On Wed, Jun 16, 2021 at 1:36 AM Lorenz Bauer <lmb@cloudflare.com> wrote:
>
> bpf2go is the Go equivalent of libbpf skeleton. The convention is that
> the compiled BPF is checked into the repository to facilitate distributing
> BPF as part of Go packages. To make this portable, bpf2go by default
> generates both bpfel and bpfeb variants of the C.
>
> Using bpf_tracing.h is inherently non-portable since the fields of
> struct pt_regs differ between platforms, so CO-RE can't help us here.
> The only way of working around this is to compile for each target
> platform independently. bpf2go can't do this by default since there
> are too many platforms.
>
> Define the various PT_... macros when no target can be determined and
> turn them into compilation failures. This works because bpf2go always
> compiles for bpf targets, so the compiler fallback doesn't kick in.
> Conditionally define __BPF_MISSING_TARGET so that we can inject a
> more appropriate error message at build time. The user can then
> choose which platform to target explicitly.
>
> Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
> ---

Applied to bpf-next, thanks.

But please use one of few "canonical" patch subject prefixes next time:
  - libbpf:
  - selftests/bpf:
  - bpftool:
  - bpf: (for kernel patches)

We don't do ":each: folder: path:" prefixes, it's not necessary and is
quite long.

>  tools/lib/bpf/bpf_tracing.h | 46 +++++++++++++++++++++++++++++++++----
>  1 file changed, 42 insertions(+), 4 deletions(-)
>

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