Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965142AbaFRI2e (ORCPT ); Wed, 18 Jun 2014 04:28:34 -0400 Received: from mailapp01.imgtec.com ([195.59.15.196]:45688 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965000AbaFRI2a (ORCPT ); Wed, 18 Jun 2014 04:28:30 -0400 Message-ID: <53A14DAA.3070207@imgtec.com> Date: Wed, 18 Jun 2014 09:28:26 +0100 From: Markos Chandras User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Alexei Starovoitov , Daniel Borkmann CC: Guenter Roeck , "linux-kernel@vger.kernel.org" , Linux MIPS Mailing List , Ralf Baechle , "Network Development" , "David S. Miller" Subject: Re: mips:allmodconfig build failure in 3.16-rc1 due to bpf_jit code References: In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [192.168.154.28] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/17/2014 08:38 PM, Alexei Starovoitov wrote: > On Tue, Jun 17, 2014 at 4:21 AM, Daniel Borkmann wrote: >> On 06/17/2014 01:09 PM, Markos Chandras wrote: >> ... >>> >>> Thanks for these instructions. I will try them myself once I find some >>> >>> time since I don't think bpf_jit for MIPS has ever been tested with all >>> the opcodes. >> >> >> Sounds great! If you find some tests are missing, please feel free to >> submit them as well via netdev. >> >> Best, >> >> Daniel > > Daniel, > > thank you for taking care of it so quickly :) > from the BPF perspective the fix looks good: > Acked-by: Alexei Starovoitov > > Markos, > > please do run the testsuite. > Doing quick code review of mips jit, it looks like: > > - your version of pkt_type_offset() will work for little endian only. > (we've recently fixed it in net/core/filter.c) > > - vlan tag handling is incorrect, since it's missing shifts. > classic BPF standard for vlan_tag_present has to return 1 or 0 > and not just emit_and(r_A, r_s0, VLAN_TAG_PRESENT, ctx); > > - pr_warn("%s: Unhandled opcode: 0x%02x\n", __FILE__, > is way too heavy, since when jit is on, unprivileged user can spam log. > > - /* sa is 5-bits long */ > BUG_ON(sa >= BIT(5)); > is wrong too. Malicious user can cause kernel crash… > Also shift A>>=33 was always allowed by classic BPF checker, so > JITs have to silently do C-equivalent version of such shift. > > - /* Determine if immediate is within the 16-bit signed range */ > static inline bool is_range16(s32 imm) > { > if (imm >= SBIT(15) || imm < -SBIT(15)) > return true; > the function name and comment are doing the opposite of > actual code, which makes harder to follow. > > - the rest looks pretty good! > > Also you'll get a lot more mileage out of mips jit if you use eBPF > instruction set as a base for JITing. You wouldn't need to worry > about vlan, pkt_type and other classic extensions. You'll get all > extensions for free, plus seccomp, tracing, etc. > > Thanks > Alexei > Hi Alexei, Thanks a lot for the feedback. I have already identified a few problems which I have already fixed. I would like to move to eBPF but I can't promise I can do it soon, so i think it's best to make sure that classic BPF works fine for 3.16 and then I will make my plans for eBPF. -- markos -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/