Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757167Ab0ANQnV (ORCPT ); Thu, 14 Jan 2010 11:43:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755351Ab0ANQnU (ORCPT ); Thu, 14 Jan 2010 11:43:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:64357 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750743Ab0ANQnU (ORCPT ); Thu, 14 Jan 2010 11:43:20 -0500 Date: Thu, 14 Jan 2010 11:42:15 -0500 From: Jason Baron To: Masami Hiramatsu Cc: Mathieu Desnoyers , Steven Rostedt , linux-kernel@vger.kernel.org, mingo@elte.hu, hpa@zytor.com, tglx@linutronix.de, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, Arjan van de Ven Subject: Re: [RFC PATCH 2/8] jump label v4 - x86: Introduce generic jump patching without stop_machine Message-ID: <20100114164215.GA2823@redhat.com> References: <1263483139.28171.3857.camel@gandalf.stny.rr.com> <20100114153908.GA3487@Krystal> <4B4F4507.2000108@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B4F4507.2000108@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1974 Lines: 54 On Thu, Jan 14, 2010 at 11:23:35AM -0500, Masami Hiramatsu wrote: > > * Steven Rostedt (rostedt@goodmis.org) wrote: > >> On Tue, 2010-01-12 at 11:26 -0500, Jason Baron wrote: > >> > >>> +/** > >>> + * text_poke_fixup() -- cross-modifying kernel text with fixup address. > >>> + * @addr: Modifying address. > >>> + * @opcode: New instruction. > >>> + * @len: length of modifying bytes. > >>> + * @fixup: Fixup address. > >>> + * > >>> + * Note: You must backup replaced instructions before calling this, > >>> + * if you need to recover it. > >>> + * Note: Must be called under text_mutex. > >>> + */ > >>> +void *__kprobes text_poke_fixup(void *addr, const void *opcode, size_t len, > >>> + void *fixup) > >>> +{ > >>> + static const unsigned char int3_insn = BREAKPOINT_INSTRUCTION; > >>> + static const int int3_size = sizeof(int3_insn); > >>> + > >>> + /* Replacing 1 byte can be done atomically. */ > >>> + if (unlikely(len <= 1)) > >>> + return text_poke(addr, opcode, len); > >> > >> This part bothers me. The text_poke just writes over the text directly > >> (using a separate mapping). But if that memory is in the pipeline of > >> another CPU, I think this could cause a GPF. > > > > It looks like we are thinking along the same lines. > > > > I'm under the impression that I pointed out this exact same issue in the > > previous round of review a few weeks ago. Does this submission reflect > > the up-to-date state of this patch ? > > No, the latest patch just skips step 3 if len == 1. > (Jason, could you update your repository?) > I thought I sent it the end of the last year ... :) > > http://lkml.org/lkml/2009/12/18/312 > > Thank you, > sorry about that...i've updated to the latest. thanks, -Jason -- 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/