Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933425AbbGGVCl (ORCPT ); Tue, 7 Jul 2015 17:02:41 -0400 Received: from mail-ig0-f182.google.com ([209.85.213.182]:33020 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932947AbbGGVCc (ORCPT ); Tue, 7 Jul 2015 17:02:32 -0400 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Tue, 7 Jul 2015 17:08:51 -0400 (EDT) To: Alexei Starovoitov cc: Vince Weaver , Masami Hiramatsu , linux-kernel@vger.kernel.org, Ananth N Mavinakayanahalli , Anil S Keshavamurthy , "David S. Miller" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Steven Rostedt Subject: Re: perf, kprobes: fuzzer generates huge number of WARNings In-Reply-To: <20150707191839.GB6040@Alexeis-MBP.westell.com> Message-ID: References: <559B3899.5040802@hitachi.com> <20150707191839.GB6040@Alexeis-MBP.westell.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1961 Lines: 41 On Tue, 7 Jul 2015, Alexei Starovoitov wrote: > On Tue, Jul 07, 2015 at 12:00:12AM -0400, Vince Weaver wrote: > > > > Well the BPF hack is in the fuzzer, not the kernel. And it's not really a > > hack, it just turned out to be a huge pain to figure out how to > > manually create a valid BPF program in conjunction with a valid kprobe > > event. > > You mean automatically generating valid bpf program? That's definitely hard. > If you mean just few hardcoded programs then take them from samples or > from test_bpf ? there's already code in trinity that in theory autogenerates bpf programs, but for now I was just trying to hook up a short known valid one. it might not be possible to really test things though, as you need to be root to create a kprobe and attach a BPF program, but my fuzzer when run as root often does all kinds of other stuff that will crash a machine. Is it ever planned to allow using bpf/kprobes without requiring full CAP_ADMIN privledges? > > I did have to sprinkle printks in the kprobe and bpf code to find out > > where various EINVAL returns were coming from, so potentially this is just > > a problem of printks happening where they shouldn't. I'll remove those > > changes and try to reproduce this tomorrow. > > could you please elaborate on this further. Which EINVALs you talking about? When you are trying to create a kprobe and bpf file there's about 10 different ways to get EINVAL as a return value and no way of knowing which one you are hitting. I added printks so I could know what issue was causing the einval. (from memory, the problems I hit were not zeroing out the attr structure, having a wrong instruction count, and a few others). Vince -- 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/