netdev - Re: arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit

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Date:   Sat, 06 May 2017 14:38:16 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     illusionist.neo@...il.com
Cc:     daniel@...earbox.net, keescook@...omium.org, mgherzan@...il.com,
        netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        linux-arm-kernel@...ts.infradead.org, ast@...com
Subject: Re: arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit

From: Shubham Bansal <illusionist.neo@...il.com>
Date: Sat, 6 May 2017 22:18:16 +0530

> Hi Daniel,
> 
> Thanks for the last reply about the testing of eBPF JIT.
> 
> I have one issue though, I am not able to find what BPF_ABS and
> BPF_IND instruction does exactly.

They are not instructions, they are modifiers for the BPF_LD
instruction which indicate an SKB load is to be performed.

You never need to ask what a BPF instruction does, it is clear
defined in the BPF interperter found in kernel/bpf/core.c

Look for the case statement LD_ABS_W and friends in __bpf_prog_run().