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 836BEC3DA6F for ; Fri, 25 Aug 2023 12:18:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238087AbjHYMSY (ORCPT ); Fri, 25 Aug 2023 08:18:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244864AbjHYMSH (ORCPT ); Fri, 25 Aug 2023 08:18:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3CFE26A2; Fri, 25 Aug 2023 05:17:48 -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 6C50967A99; Fri, 25 Aug 2023 12:16:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7D82C433CA; Fri, 25 Aug 2023 12:16:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692965812; bh=X7H370cMrbu70ojLC/1qed9YsEY4jeDtH459EHHWChI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=oZBEbEY4eyLwEqi2NMHRXR7PJWEkTkokh6JqsyPHoV+sf5Ut43NBnF2d/eLTw5/37 r77++7LSTWDSfuDXwpyNbCGO4h1D2dZAJpASShN65ZjE0HHME05fw8xOM50vyTs+5i QP3sfCGE8bzwLllof3WXm9C+/+R2CS0zHHT5uZ70rq8RI7EnC4W6oFnggpn98X3cvB xRWcPfDnxZSXWW0fk3O00fuWUrDzo7JRCgmpsPcn7RzgBxhB6svqWP67ack0Vr7upl KcmaJO1XPEufkb5DEK/SnObwm9L48a11RfD0qdNfqi/aa0l4GXPf1O7jjOSx1LqXdX oKEl3MUuRRk5g== Date: Fri, 25 Aug 2023 21:16:49 +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: [PATCH v3 1/1] tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols Message-Id: <20230825211649.188a81321f00297ec161a046@kernel.org> In-Reply-To: <20230824160859.66113-2-flaniel@linux.microsoft.com> References: <20230824160859.66113-1-flaniel@linux.microsoft.com> <20230824160859.66113-2-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 18:08:59 +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 called, because > the effectively called one has no kprobes attached. > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > This way, user needs to use address to remove the ambiguity. > > Suggested-by: Masami Hiramatsu > Signed-off-by: Francis Laniel > Link: https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@kernel.org/ > --- Ah, this should be fine, but selftest (tools/testing/selftests/ftrace) fails. # tail 60-kprobe_module.tc-log.vsOHnF ... + : + : 'Add an event on a module function without specifying event name' + : + echo 'p trace_printk:trace_printk_irq_work' sh: write error: No such file or directory Ah, the function on non-exist module should be checked too. # tail 63-kprobe_syntax_errors.tc-log.mMLwIQ + + printfwc '%s' -c 'p ' + pos=2 + printf+ '%s'tr 'p ^non_exist_func' -d ^ + command='p non_exist_func' + echo 'Test command: p non_exist_func' Test command: p non_exist_func + echo + grep 'trace_kprobe: error:' -A 3 error_log Also, this doesn't leave a syntax error message. So, the below changes are needed. diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 8ab46a2a446d..1e57bc896952 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -855,7 +855,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) } } - if (symbol) { + if (symbol && !strchr(symbol, ':')) { unsigned int count; count = number_of_same_symbols(symbol); @@ -864,6 +864,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) * Users should use ADDR to remove the ambiguity of * using KSYM only. */ + trace_probe_log_err(0, NON_UNIQ_SYMBOL); ret = -EADDRNOTAVAIL; goto error; @@ -872,6 +873,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) * We can return ENOENT earlier than when register the * kprobe. */ + trace_probe_log_err(0, BAD_PROBE_ADDR); ret = -ENOENT; goto error; diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 7f929482e8d4..a4f478448eef 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -450,6 +450,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, C(BAD_MAXACT, "Invalid maxactive number"), \ C(MAXACT_TOO_BIG, "Maxactive is too big"), \ C(BAD_PROBE_ADDR, "Invalid probed address or symbol"), \ + C(NON_UNIQ_SYMBOL, "The symbol is not unique"), \ C(BAD_RETPROBE, "Retprobe address must be an function entry"), \ C(NO_TRACEPOINT, "Tracepoint is not found"), \ C(BAD_ADDR_SUFFIX, "Invalid probed address suffix"), \ Thank you, > kernel/trace/trace_kprobe.c | 61 +++++++++++++++++++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 23dba01831f7..2f393739e8cf 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 number_of_same_symbols(char *func_name) > +{ > + unsigned int count; > + > + count = 0; > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > + > + return count; > +} > + > static int __trace_kprobe_create(int argc, const char *argv[]) > { > /* > @@ -836,6 +855,29 @@ static int __trace_kprobe_create(int argc, const char *argv[]) > } > } > > + if (symbol) { > + unsigned int count; > + > + count = number_of_same_symbols(symbol); > + if (count > 1) { > + /* > + * Users should use ADDR to remove the ambiguity of > + * using KSYM only. > + */ > + ret = -EADDRNOTAVAIL; > + > + goto error; > + } else if (count == 0) { > + /* > + * We can return ENOENT earlier than when register the > + * kprobe. > + */ > + ret = -ENOENT; > + > + goto error; > + } > + } > + > trace_probe_log_set_index(0); > if (event) { > ret = traceprobe_parse_event_name(&event, &group, gbuf, > @@ -1699,6 +1741,7 @@ 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 +1752,24 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs, > int ret; > char *event; > > + if (func) { > + unsigned int count; > + > + count = number_of_same_symbols(func); > + if (count > 1) > + /* > + * Users should use addr to remove the ambiguity of > + * using func only. > + */ > + return ERR_PTR(-EADDRNOTAVAIL); > + else if (count == 0) > + /* > + * We can return ENOENT earlier than when register the > + * kprobe. > + */ > + return ERR_PTR(-ENOENT); > + } > + > /* > * 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)