From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: [RFCv2 07/16] bpf: enable non-core use of the verfier Date: Tue, 30 Aug 2016 13:48:27 -0700 Message-ID: <20160830204826.GA71063@ast-mbp.thefacebook.com> References: <1472234775-29453-1-git-send-email-jakub.kicinski@netronome.com> <1472234775-29453-8-git-send-email-jakub.kicinski@netronome.com> <20160826232904.GA28873@ast-mbp.thefacebook.com> <20160827124004.43728202@jkicinski-Precision-T1700> <20160827173250.GA38477@ast-mbp> <57C4976C.4010501@iogearbox.net> <57C49846.1080608@iogearbox.net> <20160830124854.76e5a1c3@laptop> <57C5D986.2000402@iogearbox.net> <20160830222246.29e3f3cc@laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Daniel Borkmann , Jakub Kicinski , netdev@vger.kernel.org, ast@kernel.org, dinan.gunawardena@netronome.com, jiri@resnulli.us, john.fastabend@gmail.com To: Jakub Kicinski Return-path: Received: from mail-pa0-f44.google.com ([209.85.220.44]:36543 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751202AbcH3Usb (ORCPT ); Tue, 30 Aug 2016 16:48:31 -0400 Received: by mail-pa0-f44.google.com with SMTP id fu3so3069705pad.3 for ; Tue, 30 Aug 2016 13:48:30 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20160830222246.29e3f3cc@laptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Aug 30, 2016 at 10:22:46PM +0200, Jakub Kicinski wrote: > 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. if xor matching is only need for classic, I would drop that patch just to avoid unnecessary state collection. The number of lines is not a concern, but extra state for state prunning is. > Alternatively - is there any eBPF assembler out there? Something > converting verifier output back into ELF would be quite cool. would certainly be nice. I don't think there is anything standalone. btw llvm can be made to work as assembler only, but simple flex/bison is probably better.