Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752240AbaGBXf0 (ORCPT ); Wed, 2 Jul 2014 19:35:26 -0400 Received: from mail-ie0-f179.google.com ([209.85.223.179]:33764 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751134AbaGBXfY (ORCPT ); Wed, 2 Jul 2014 19:35:24 -0400 MIME-Version: 1.0 In-Reply-To: References: <1403913966-4927-1-git-send-email-ast@plumgrid.com> <1403913966-4927-9-git-send-email-ast@plumgrid.com> Date: Wed, 2 Jul 2014 16:35:23 -0700 Message-ID: Subject: Re: [PATCH RFC net-next 08/14] bpf: add eBPF verifier From: Chema Gonzalez To: Alexei Starovoitov Cc: "David S. Miller" , Ingo Molnar , Linus Torvalds , Steven Rostedt , Daniel Borkmann , Eric Dumazet , Peter Zijlstra , Arnaldo Carvalho de Melo , Jiri Olsa , Thomas Gleixner , "H. Peter Anvin" , Andrew Morton , Kees Cook , Linux API , Network Development , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 2, 2014 at 4:04 PM, Alexei Starovoitov wrote: >>> + reg = regs + BPF_REG_1; /* 1st arg to a function */ >>> + reg->ptr = PTR_TO_CTX; >> Wait, doesn't this depend on doing "BPF_MOV64_REG(BPF_REG_CTX, >> BPF_REG_ARG1)" (the bpf-to-ebpf prologue), which is only enforced on >> filters converted from bpf? In fact, shouldn't this set >> regs[BPF_REG_CTX] instead of regs[BPF_REG_1] ? > > nope. it's REG_1. > as you said r6=r1 is only emitted by converted classic filters. > Verifier will see this 'r6=r1' assignment and will copy the r1 type into r6. You're right. I read BPF_MOV64_REG() AT&T-syntax-style. BTW, check_stack_write() in kernel/bpf/verifier.c has a couple of assignments of a slot->ptr to 0 (instead of INVALID_PTR). I assume this is unintended. -Chema -- 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/