linux-kernel - Re: [RFC PATCH v3 16/37] bpf tools: Collect eBPF programs from their own sections

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Message-ID: <555A3027.7060803@plumgrid.com>
Date:	Mon, 18 May 2015 11:32:07 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>,
	Namhyung Kim <namhyung@...nel.org>
CC:	paulus@...ba.org, a.p.zijlstra@...llo.nl, mingo@...hat.com,
	acme@...nel.org, jolsa@...nel.org, dsahern@...il.com,
	daniel@...earbox.net, brendan.d.gregg@...il.com,
	masami.hiramatsu.pt@...achi.com, lizefan@...wei.com,
	linux-kernel@...r.kernel.org, pi3orama@....com
Subject: Re: [RFC PATCH v3 16/37] bpf tools: Collect eBPF programs from their
 own sections

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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