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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15514C77B7F for ; Tue, 16 May 2023 04:25:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229543AbjEPEZM (ORCPT ); Tue, 16 May 2023 00:25:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229622AbjEPEZL (ORCPT ); Tue, 16 May 2023 00:25:11 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE32E199D; Mon, 15 May 2023 21:25:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7FE8D625E2; Tue, 16 May 2023 04:25:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92322C433D2; Tue, 16 May 2023 04:25:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684211106; bh=9wMxAD6PoHOqDdlWCO7opXIh2VlJBRBjZmgi4WFmsCY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=oK8Re3tiMtXuYviAqv9wSkvE2UgQAABR0Kf7JQJcDiUmz+dY2toTnDFVj3aBl1Gee pYITTkATnkx08Zjdy2ZRGCThhFrkNWnpcixE90k1tuVataacTYaGFQEWfHl4U4zPN+ USgs20h3bxkJ9cnyGdoM8yROcYYDoHdX6yfJNffAXGQsH/D07GEj/6GDckKLcWPWsY un8XntvPTuMiCCOMRAEy+oxAoaz7IOt2mXHOtkq5Mb+z0LMiufgWBuYqgE3ThIuHd/ Y9wL6FL0zIrkApWl/TY4h2DY7JTo5Clc1PU6xKMK0hVHoMG2qDp8T/CXwR4UNUAem9 SDp5MgvUZsSJg== Date: Tue, 16 May 2023 13:25:02 +0900 From: Masami Hiramatsu (Google) To: Ze Gao Cc: Steven Rostedt , Ze Gao , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler Message-Id: <20230516132502.c51be728bd086b8c9005ce57@kernel.org> In-Reply-To: References: X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org Hi Ze Gao, Thanks for the patch. On Mon, 15 May 2023 11:26:38 +0800 Ze Gao wrote: > This patch replace preempt_{disable, enable} with its corresponding > notrace version in rethook_trampoline_handler so no worries about stack > recursion or overflow introduced by preempt_count_{add, sub} under > fprobe + rethook context. So, have you ever see that recursion of preempt_count overflow case? I intended to use the normal preempt_disable() here because it does NOT prohibit any function-trace call (Note that both kprobes and fprobe checks recursive call by itself) but it is used for preempt_onoff tracer. Thanks, > > Signed-off-by: Ze Gao > --- > kernel/trace/rethook.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c > index 32c3dfdb4d6a..60f6cb2b486b 100644 > --- a/kernel/trace/rethook.c > +++ b/kernel/trace/rethook.c > @@ -288,7 +288,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs, > * These loops must be protected from rethook_free_rcu() because those > * are accessing 'rhn->rethook'. > */ > - preempt_disable(); > + preempt_disable_notrace(); > > /* > * Run the handler on the shadow stack. Do not unlink the list here because > @@ -321,7 +321,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs, > first = first->next; > rethook_recycle(rhn); > } > - preempt_enable(); > + preempt_enable_notrace(); > > return correct_ret_addr; > } > -- > 2.40.1 > -- Masami Hiramatsu (Google)