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 8F33EC3DA6F for ; Fri, 25 Aug 2023 12:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244879AbjHYMfq (ORCPT ); Fri, 25 Aug 2023 08:35:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58968 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244893AbjHYMfW (ORCPT ); Fri, 25 Aug 2023 08:35:22 -0400 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 764562705; Fri, 25 Aug 2023 05:34:57 -0700 (PDT) Received: from pwmachine.localnet (85-170-34-233.rev.numericable.fr [85.170.34.233]) by linux.microsoft.com (Postfix) with ESMTPSA id 0C0AA2127C8E; Fri, 25 Aug 2023 05:34:51 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 0C0AA2127C8E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1692966893; bh=gDGh0UP0Bb3Xu6IBJ+SaHnBTtH5Z3mRhSnZ9hCl/VJY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kFLqG5xnQ+QUCj2dIccwFigMQDJXrHKj82+xsopQ+nkG2SdsagAt+opnHFj8SAnEK ZmIwQ3eOQBCyDrJoIaLQskOVZdEwedRu7fYeAEsMed+Vilqw+e9torjthCj0ueIBTP u3/Mo+X4Y31ux/pdjXZEzdKM5Wa75V6kVhDyGnwM= From: Francis Laniel To: Masami Hiramatsu 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 Date: Fri, 25 Aug 2023 14:34:49 +0200 Message-ID: <5704161.DvuYhMxLoT@pwmachine> In-Reply-To: <20230825211649.188a81321f00297ec161a046@kernel.org> References: <20230824160859.66113-1-flaniel@linux.microsoft.com> <20230824160859.66113-2-flaniel@linux.microsoft.com> <20230825211649.188a81321f00297ec161a046@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. Le vendredi 25 ao=FBt 2023, 14:16:49 CEST Masami Hiramatsu a =E9crit : > On Thu, 24 Aug 2023 18:08:59 +0200 >=20 > 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. > >=20 > > So, this commit returns EADDRNOTAVAIL when func matches several symbols. > > This way, user needs to use address to remove the ambiguity. > >=20 > > Suggested-by: Masami Hiramatsu > > Signed-off-by: Francis Laniel > > Link: > > https://lore.kernel.org/lkml/20230819101105.b0c104ae4494a7d1f2eea742@ke= rn > > el.org/ --- >=20 > Ah, this should be fine, but selftest (tools/testing/selftests/ftrace) > fails. >=20 > # 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 >=20 > Ah, the function on non-exist module should be checked too. >=20 > # tail 63-kprobe_syntax_errors.tc-log.mMLwIQ > + + printfwc '%s' -c > 'p ' > + pos=3D2 > + printf+ '%s'tr 'p ^non_exist_func' > -d ^ > + command=3D'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 >=20 > Also, this doesn't leave a syntax error message. >=20 > So, the below changes are needed. Excellent catch! Thank you, I will apply this patch and send v4 right after. Regarding test, do you think I can add a test for the EADDRNOTAVAIL case? Maybe it should go inside LTP? As this would need having a kernel compiled= =20 with a name pointing to several symbols? Also, should some man pages somewhere be updated to reflect the case kprobe= can=20 return EADDRNOTAVAIL? > 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[]) } > } >=20 > - if (symbol) { > + if (symbol && !strchr(symbol, ':')) { > unsigned int count; >=20 > count =3D 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 =3D -EADDRNOTAVAIL; >=20 > 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 =3D -ENOENT; >=20 > 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=20 entry"), \ > C(NO_TRACEPOINT, "Tracepoint is not found"), \ > C(BAD_ADDR_SUFFIX, "Invalid probed address suffix"), \ >=20 > Thank you, >=20 > > kernel/trace/trace_kprobe.c | 61 +++++++++++++++++++++++++++++++++++++ > > 1 file changed, 61 insertions(+) > >=20 > > 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_n= b =3D > > {>=20 > > .priority =3D 1 /* Invoked after kprobe module callback */ > > =20 > > }; > >=20 > > +static int count_symbols(void *data, unsigned long unused) > > +{ > > + unsigned int *count =3D data; > > + > > + (*count)++; > > + > > + return 0; > > +} > > + > > +static unsigned int number_of_same_symbols(char *func_name) > > +{ > > + unsigned int count; > > + > > + count =3D 0; > > + kallsyms_on_each_match_symbol(count_symbols, func_name, &count); > > + > > + return count; > > +} > > + > >=20 > > static int __trace_kprobe_create(int argc, const char *argv[]) > > { > > =20 > > /* > >=20 > > @@ -836,6 +855,29 @@ static int __trace_kprobe_create(int argc, const c= har > > *argv[])>=20 > > } > > =09 > > } > >=20 > > + if (symbol) { > > + unsigned int count; > > + > > + count =3D number_of_same_symbols(symbol); > > + if (count > 1) { > > + /* > > + * Users should use ADDR to remove the ambiguity of > > + * using KSYM only. > > + */ > >=20 > >=20 > >=20 > > + ret =3D -EADDRNOTAVAIL; > > + > > + goto error; > > + } else if (count =3D=3D 0) { > > + /* > > + * We can return ENOENT earlier than when register the > > + * kprobe. > > + */ > > + ret =3D -ENOENT; > > + > > + goto error; > > + } > > + } > > + > >=20 > > trace_probe_log_set_index(0); > > if (event) { > > =09 > > ret =3D traceprobe_parse_event_name(&event, &group, gbuf, > >=20 > > @@ -1699,6 +1741,7 @@ static int unregister_kprobe_event(struct > > trace_kprobe *tk)>=20 > > } > > =20 > > #ifdef CONFIG_PERF_EVENTS > >=20 > > + > >=20 > > /* 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, > >=20 > > @@ -1709,6 +1752,24 @@ create_local_trace_kprobe(char *func, void *addr, > > unsigned long offs,>=20 > > int ret; > > char *event; > >=20 > > + if (func) { > > + unsigned int count; > > + > > + count =3D 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 =3D=3D 0) > > + /* > > + * We can return ENOENT earlier than when register the > > + * kprobe. > > + */ > > + return ERR_PTR(-ENOENT); > > + } > > + > >=20 > > /* > > =09 > > * local trace_kprobes are not added to dyn_event, so they are never > > * searched in find_trace_kprobe(). Therefore, there is no concern of Best regards.