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 6F698C7113B for ; Thu, 24 Aug 2023 13:03:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231657AbjHXNC6 (ORCPT ); Thu, 24 Aug 2023 09:02:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237813AbjHXNCf (ORCPT ); Thu, 24 Aug 2023 09:02:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8396CE79; Thu, 24 Aug 2023 06:02:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 008D664AF8; Thu, 24 Aug 2023 13:02:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2163C433C7; Thu, 24 Aug 2023 13:02:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692882152; bh=q2az01/KAgq/cnwVEoG/mArWYoVRqcX7JTqR4RkwD9o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=exrNO0cyE7+gD8isFveY8zJlFYKrFIHi+EBtj8pEu1J7XJt+8j9kFwpezxlM+4xRd QQ9RjWPFwIIx8VO3lNkhUqgkcE+bOpJgSi/TJzxgdikmDVBADeucuGZ44kfEdVG6Ku K34FRTCANLETF/b+Vsw6D2PTMAooRECfaqZgc9VVeVEM475v6oqfqBkEn8kg3RFEad Z1cmnOKK+wEr3JRJ0rDk8lSgo8lwCa4c9wEZw6IXKjzlfm2wgdW/QHTGTdYXHA7e5w Rok54at1yG/NjoYu0L5iqDGorJAy4mszNRIqP5dIfFB9Ad7EOMgy01VZ4Cd0rsUseC Vy1JH8IcvvXTA== Date: Thu, 24 Aug 2023 22:02:27 +0900 From: Masami Hiramatsu (Google) To: Francis Laniel Cc: linux-kernel@vger.kernel.org, Masami Hiramatsu , linux-trace-kernel@vger.kernel.org, Steven Rostedt Subject: Re: [RFC PATCH v2 1/1] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols Message-Id: <20230824220227.01c367c1d7b6219a79cf2843@kernel.org> In-Reply-To: <20230824103734.53453-2-flaniel@linux.microsoft.com> References: <20230824103734.53453-1-flaniel@linux.microsoft.com> <20230824103734.53453-2-flaniel@linux.microsoft.com> X-Mailer: Sylpheed 3.7.0 (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 Thu, 24 Aug 2023 12:37:34 +0200 Francis Laniel wrote: > Previously to this commit, if func matches several symbols, a kprobe, being > either sysfs or PMU, would only be installed for the first matching address. > This could lead to some misunderstanding when some BPF code was never called > because it was attached to a function which was indeed not call, because the > effectively called one has no kprobes. > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > This way, user needs to use addr to remove the ambiguity. Thanks for update the patch. I have some comments there. > > Suggested-by: Masami Hiramatsu > Signed-off-by: Francis Laniel > Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ > --- > kernel/trace/trace_kprobe.c | 42 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 23dba01831f7..0c8dd6ba650b 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -705,6 +705,25 @@ static struct notifier_block trace_kprobe_module_nb = { > .priority = 1 /* Invoked after kprobe module callback */ > }; > > +static int count_symbols(void *data, unsigned long unused) > +{ > + unsigned int *count = data; > + > + (*count)++; > + > + return 0; > +} > + > +static unsigned int func_name_several_symbols(char *func_name) If this returns boolean, please use 'bool' for return type. Also, I think 'func_name_is_unique()' is more natural. > +{ > + unsigned int count; > + > + count = 0; > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > + > + return count > 1; > +} > + > static int __trace_kprobe_create(int argc, const char *argv[]) > { > /* > @@ -836,6 +855,18 @@ static int __trace_kprobe_create(int argc, const char *argv[]) > } > } > > + /* > + * If user specifies KSYM, we check it does not correspond to several > + * symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use ADDR rather than KSYM to remove the ambiguity. > + */ > + if (symbol && func_name_several_symbols(symbol)) { Then, here will be if (symbol && !func_name_is_unique(symbol)) { > + ret = -EADDRNOTAVAIL; > + > + goto error; > + } > + > trace_probe_log_set_index(0); > if (event) { > ret = traceprobe_parse_event_name(&event, &group, gbuf, > @@ -1699,6 +1730,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) > } > > #ifdef CONFIG_PERF_EVENTS > + > /* create a trace_kprobe, but don't add it to global lists */ > struct trace_event_call * > create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > @@ -1709,6 +1741,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > int ret; > char *event; > > + /* > + * If user specifies func, we check that function name does not > + * correspond to several symbols. > + * If this is the case, we return EADDRNOTAVAIL to indicate the user > + * he/she should use addr and offs rather than func to remove the > + * ambiguity. > + */ > + if (func && func_name_several_symbols(func)) Ditto. Thanks! > + return ERR_PTR(-EADDRNOTAVAIL); > + > /* > * local trace_kprobes are not added to dyn_event, so they are never > * searched in find_trace_kprobe(). Therefore, there is no concern of > -- > 2.34.1 > -- Masami Hiramatsu (Google)