From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D5F3C38A2A for ; Fri, 8 May 2020 13:27:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1167624958 for ; Fri, 8 May 2020 13:27:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588944479; bh=XmKr+actPKIyBSF7+MJNsc70eQDYMdbsWtd71MQ4z8o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=T+PwP4q8fFb5VYUaTPWWqCpyym9tKZfEJ2W3CQ+wHngTUrFonoHeKWwvcHW4P1AvC hfRgH4E6NnmmKzw9P4XSFfEuBf66kwPNSaNGdCz7fKjmlLmkJC3NpjX4Ckq9SgwK2i uxAwjbPrbWMKAbFzNRtBH/xKN9XCapIAQPpEcrGo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727964AbgEHN16 (ORCPT ); Fri, 8 May 2020 09:27:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:50096 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbgEHN15 (ORCPT ); Fri, 8 May 2020 09:27:57 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DC57024953; Fri, 8 May 2020 13:27:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588944477; bh=XmKr+actPKIyBSF7+MJNsc70eQDYMdbsWtd71MQ4z8o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=OYg5EcUy5J7fNhWiDvM5ZKpmTJRL9DKvTrTcXTEdc6xz2hCkG0mdPoNVFHZ7r1uRH fNBfP+EGrEG7ysIj/kfXDidRX6YkYZNZPo4XQyFVdOmysrCJxjyuYPzNCClroTi/+w 0mjbsYbVE85F3wPCuxZTkDZ8XFCRP8952LksoUO8= Date: Fri, 8 May 2020 22:27:50 +0900 From: Masami Hiramatsu To: Thomas Gleixner Cc: LKML , x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , "Peter Zijlstra (Intel)" Subject: Re: [patch V4 part 4 02/24] x86/int3: Avoid atomic instrumentation Message-Id: <20200508222750.a7aca9f898b7637d402e8726@kernel.org> In-Reply-To: <20200505135313.517429268@linutronix.de> References: <20200505134926.578885807@linutronix.de> <20200505135313.517429268@linutronix.de> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 05 May 2020 15:49:28 +0200 Thomas Gleixner wrote: > From: Peter Zijlstra > > Use arch_atomic_*() and READ_ONCE_NOCHECK() to ensure nothing untoward > creeps in and ruins things. > > That is; this is the INT3 text poke handler, strictly limit the code > that runs in it, lest it inadvertenly hits yet another INT3. > > Reported-by: Thomas Gleixner > Signed-off-by: Peter Zijlstra (Intel) > Signed-off-by: Thomas Gleixner Looks good to me. Reviewed-by: Masami Hiramatsu > --- > arch/x86/kernel/alternative.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > --- a/arch/x86/kernel/alternative.c > +++ b/arch/x86/kernel/alternative.c > @@ -960,9 +960,9 @@ static struct bp_patching_desc *bp_desc; > static __always_inline > struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp) > { > - struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */ > + struct bp_patching_desc *desc = READ_ONCE_NOCHECK(*descp); /* rcu_dereference */ > > - if (!desc || !atomic_inc_not_zero(&desc->refs)) > + if (!desc || !arch_atomic_inc_not_zero(&desc->refs)) > return NULL; > > return desc; > @@ -971,7 +971,7 @@ struct bp_patching_desc *try_get_desc(st > static __always_inline void put_desc(struct bp_patching_desc *desc) > { > smp_mb__before_atomic(); > - atomic_dec(&desc->refs); > + arch_atomic_dec(&desc->refs); > } > > static __always_inline void *text_poke_addr(struct text_poke_loc *tp) > -- Masami Hiramatsu