netdev - Re: eBPF - little-endian load instructions?

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Date:   Sat, 15 Apr 2017 09:06:11 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: eBPF - little-endian load instructions?

On Fri, 2017-04-14 at 11:42 -0700, Alexei Starovoitov wrote:

> bpf takes endianness of the cpu it runs on.

Ok, so then things are actually not as difficult as I thought.

> if we said that bpf 32-bit load insn is little endian, it would have
> screwed up all big-endian archs and the other way around.

Right.

But then basically we do only need to have builtins for endian
conversion, and #define them appropriately, as done anywhere else.

Perhaps we want to eventually be able to take advantage of "other-
endian" loads the CPU may have through the JIT, but getting it correct
first would be good :)

Either way though, it could be done with something like inline
assembly.

johannes