netdev - Re: [RFCv2 07/16] bpf: enable non-core use of the verfier

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Date:   Tue, 30 Aug 2016 22:22:46 +0200
From:   Jakub Kicinski <kubakici@...pl>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        netdev@...r.kernel.org, ast@...nel.org,
        dinan.gunawardena@...ronome.com, jiri@...nulli.us,
        john.fastabend@...il.com
Subject: Re: [RFCv2 07/16] bpf: enable non-core use of the verfier

On Tue, 30 Aug 2016 21:07:50 +0200, Daniel Borkmann wrote:
> > Having two modes seems more straight forward and I think we would only
> > need to pay attention in the LD_IMM64 case, I don't think I've seen
> > LLVM generating XORs, it's just the cBPF -> eBPF conversion.  
> 
> Okay, though, I think that the cBPF to eBPF migration wouldn't even
> pass through the bpf_parse() handling, since verifier is not aware on
> some of their aspects such as emitting calls directly (w/o *proto) or
> arg mappings. Probably make sense to reject these (bpf_prog_was_classic())
> if they cannot be handled anyway?

TBH again I only use cBPF for testing.  It's a convenient way of
generating certain instruction sequences.  I can probably just drop
it completely but the XOR patch is just 3 lines of code so not a huge
cost either...  I'll keep patch 6 in my tree for now.  

Alternatively - is there any eBPF assembler out there?  Something
converting verifier output back into ELF would be quite cool.