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From:   =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, bpf@vger.kernel.org,
        netdev@vger.kernel.org
Cc:     =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@rivosinc.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        linux-kselftest@vger.kernel.org,
        Anders Roxell <anders.roxell@linaro.org>,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH bpf-next] selftests/bpf: Cross-compile bpftool
In-Reply-To: <20230210084326.1802597-1-bjorn@kernel.org>
References: <20230210084326.1802597-1-bjorn@kernel.org>
Date:   Mon, 13 Feb 2023 15:30:48 +0100
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Bj=C3=B6rn T=C3=B6pel <bjorn@kernel.org> writes:

> From: Bj=C3=B6rn T=C3=B6pel <bjorn@rivosinc.com>
>
> When the BPF selftests are cross-compiled, only the a host version of
> bpftool is built. This version of bpftool is used to generate various
> intermediates, e.g., skeletons.
>
> The test runners are also using bpftool. The Makefile will symlink
> bpftool from the selftest/bpf root, where the test runners will look
> for the tool:
>
>   | ...
>   | $(Q)ln -sf $(if $2,..,.)/tools/build/bpftool/bootstrap/bpftool \
>   |    $(OUTPUT)/$(if $2,$2/)bpftool
>
> There are two issues for cross-compilation builds:
>
>  1. There is no native (cross-compilation target) build of bpftool
>  2. The bootstrap variant of bpftool is never cross-compiled (by
>     design)
>
> Make sure that a native/cross-compiled version of bpftool is built,
> and if CROSS_COMPILE is set, symlink to the native/non-bootstrap
> version.

...and the grand master plan is to add BPF CI support for riscv64, where
this patch a prerequisite to [1]. I would suspect that other platforms
might benefit from cross-compilation builds as well.

[1] https://github.com/kernel-patches/vmtest/pull/194