Message-ID: <555A3027.7060803@plumgrid.com>
Date: Mon, 18 May 2015 11:32:07 -0700
From: Alexei Starovoitov <ast@plumgrid.com>
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To: "Wangnan (F)" <wangnan0@huawei.com>, Namhyung Kim <namhyung@kernel.org>
CC: paulus@samba.org, a.p.zijlstra@chello.nl, mingo@redhat.com,
        acme@kernel.org, jolsa@kernel.org, dsahern@gmail.com,
        daniel@iogearbox.net, brendan.d.gregg@gmail.com,
        masami.hiramatsu.pt@hitachi.com, lizefan@huawei.com,
        linux-kernel@vger.kernel.org, pi3orama@163.com
Subject: Re: [RFC PATCH v3 16/37] bpf tools: Collect eBPF programs from their
 own sections
References: <1431860222-61636-1-git-send-email-wangnan0@huawei.com> <1431860222-61636-17-git-send-email-wangnan0@huawei.com> <20150518122922.GB7683@danjae.kornet> <5559DF59.6080107@huawei.com>
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On 5/18/15 5:47 AM, Wangnan (F) wrote:
>
>
>>> +    prog->insns_cnt = size / sizeof(struct bpf_insn);
>>> +    memcpy(prog->insns, data,
>>> +           prog->insns_cnt * sizeof(struct bpf_insn));
>> Doesn't the data need to be swapped?
>>
>> Thanks,
>> Namhyung
>>
>
> I'm not very sure, since they are instructions. Byte order of
> instructions and byte order of data
> are not always same. Think about ARM. Therefore another choice is to
> swap them in kernel,
> keep user-kernel interface clean.
>
> Alexei Starovoitov, do you think we should use uniformed instruction
> byte order in both big and little
> endian kernel on user-kernel interface, or let userspace feed swapped
> instructions to kernel if
> endianess is not match?

see my reply to the other patch. endianness is the job of llvm.
Let's fix it there.

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