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 6A848C77B7D for ; Tue, 16 May 2023 01:25:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229544AbjEPBZx (ORCPT ); Mon, 15 May 2023 21:25:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229514AbjEPBZw (ORCPT ); Mon, 15 May 2023 21:25:52 -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 F27C71FDC; Mon, 15 May 2023 18:25:50 -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 8864C633E5; Tue, 16 May 2023 01:25:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65E39C433D2; Tue, 16 May 2023 01:25:49 +0000 (UTC) Date: Mon, 15 May 2023 21:25:46 -0400 From: Steven Rostedt To: Ze Gao Cc: Masami Hiramatsu , Ze Gao , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 2/4] fprobe: make fprobe_kprobe_handler recursion free Message-ID: <20230515212546.7a467a1f@gandalf.local.home> In-Reply-To: <6c428b9f74090b2780b67ca498c45aa5e8c38c44.1684120990.git.zegao@tencent.com> References: <6c428b9f74090b2780b67ca498c45aa5e8c38c44.1684120990.git.zegao@tencent.com> X-Mailer: Claws Mail 3.17.8 (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 On Mon, 15 May 2023 11:26:39 +0800 Ze Gao wrote: > Current implementation calls kprobe related functions before doing > ftrace recursion check in fprobe_kprobe_handler, which opens door > to kernel crash due to stack recursion if preempt_count_{add, sub} > is traceable. > > Refactor the common part out of fprobe_kprobe_handler and fprobe_ > handler and call ftrace recursion detection at the very beginning, > and also mark these functions notrace so that the whole fprobe_k- > probe_handler is free from recusion. And > > Signed-off-by: Ze Gao > --- > kernel/trace/fprobe.c | 61 +++++++++++++++++++++++++++++++------------ > 1 file changed, 45 insertions(+), 16 deletions(-) > > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c > index 9abb3905bc8e..ad9a36c87ad9 100644 > --- a/kernel/trace/fprobe.c > +++ b/kernel/trace/fprobe.c > @@ -20,30 +20,22 @@ struct fprobe_rethook_node { > char data[]; > }; > > -static void fprobe_handler(unsigned long ip, unsigned long parent_ip, > - struct ftrace_ops *ops, struct ftrace_regs *fregs) > +static inline notrace void __fprobe_handler(unsigned long ip, unsigned long FYI, if you look in kernel/trace/Makefile you'll see: ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE) Which removes the flags to add tracing. So there's no reason to add "notrace" here, as all functions in this directory are by default "notrace". -- Steve > + parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs) > { > struct fprobe_rethook_node *fpr; > struct rethook_node *rh = NULL; > struct fprobe *fp; > void *entry_data = NULL; > - int bit, ret; > + int ret; > > fp = container_of(ops, struct fprobe, ops); > - if (fprobe_disabled(fp)) > - return; > - > - bit = ftrace_test_recursion_trylock(ip, parent_ip); > - if (bit < 0) { > - fp->nmissed++; > - return; > - } > > if (fp->exit_handler) { > rh = rethook_try_get(fp->rethook); > if (!rh) { > fp->nmissed++; > - goto out; > + return; > } > fpr = container_of(rh, struct fprobe_rethook_node, node); > fpr->entry_ip = ip; > @@ -61,23 +53,60 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip, > else > rethook_hook(rh, ftrace_get_regs(fregs), true); > } >