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 130BAC4332F for ; Fri, 22 Apr 2022 16:32:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1449734AbiDVQff (ORCPT ); Fri, 22 Apr 2022 12:35:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1389617AbiDVQfe (ORCPT ); Fri, 22 Apr 2022 12:35:34 -0400 Received: from www62.your-server.de (www62.your-server.de [213.133.104.62]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25DE95F24A; Fri, 22 Apr 2022 09:32:41 -0700 (PDT) Received: from sslproxy02.your-server.de ([78.47.166.47]) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1nhwCv-0001kP-Ev; Fri, 22 Apr 2022 18:32:33 +0200 Received: from [85.1.206.226] (helo=linux.home) by sslproxy02.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nhwCv-000C8l-5l; Fri, 22 Apr 2022 18:32:33 +0200 Subject: Re: [PATCH bpf-next] libbpf: also check /sys/kernel/tracing for tracefs files To: Connor O'Brien , Alexei Starovoitov , Andrii Nakryiko Cc: Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220421201125.13907-1-connoro@google.com> From: Daniel Borkmann Message-ID: <407ab3dd-cee1-a043-585b-1b2886c6f7fd@iogearbox.net> Date: Fri, 22 Apr 2022 18:32:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20220421201125.13907-1-connoro@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.103.5/26520/Fri Apr 22 10:30:17 2022) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/21/22 10:11 PM, Connor O'Brien wrote: > libbpf looks for tracefs files only under debugfs, but tracefs may be > mounted even if debugfs is not. When /sys/kernel/debug/tracing is > absent, try looking under /sys/kernel/tracing instead. > > Signed-off-by: Connor O'Brien > --- > tools/lib/bpf/libbpf.c | 26 +++++++++++++++++++------- > 1 file changed, 19 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 68cc134d070d..6ef587329eb2 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -10140,10 +10140,16 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, > __sync_fetch_and_add(&index, 1)); > } > > +static bool debugfs_available(void) > +{ > + return !access("/sys/kernel/debug/tracing", F_OK); Should this be a one-time probe, so on subsequent debugfs_available() calls we return the initially cached result? > +} > + > static int add_kprobe_event_legacy(const char *probe_name, bool retprobe, > const char *kfunc_name, size_t offset) > { > - const char *file = "/sys/kernel/debug/tracing/kprobe_events"; > + const char *file = debugfs_available() ? "/sys/kernel/debug/tracing/kprobe_events" : > + "/sys/kernel/tracing/kprobe_events"; > > return append_to_file(file, "%c:%s/%s %s+0x%zx", > retprobe ? 'r' : 'p', > @@ -10153,7 +10159,8 @@ static int add_kprobe_event_legacy(const char *probe_name, bool retprobe, > > static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe) > { > - const char *file = "/sys/kernel/debug/tracing/kprobe_events"; > + const char *file = debugfs_available() ? "/sys/kernel/debug/tracing/kprobe_events" : > + "/sys/kernel/tracing/kprobe_events"; > > return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name); > } > @@ -10163,7 +10170,8 @@ static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retpro > char file[256]; > > snprintf(file, sizeof(file), > - "/sys/kernel/debug/tracing/events/%s/%s/id", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > retprobe ? "kretprobes" : "kprobes", probe_name); > > return parse_uint_from_file(file, "%d\n"); > @@ -10493,7 +10501,8 @@ static void gen_uprobe_legacy_event_name(char *buf, size_t buf_sz, > static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe, > const char *binary_path, size_t offset) > { > - const char *file = "/sys/kernel/debug/tracing/uprobe_events"; > + const char *file = debugfs_available() ? "/sys/kernel/debug/tracing/uprobe_events" : > + "/sys/kernel/tracing/uprobe_events"; > > return append_to_file(file, "%c:%s/%s %s:0x%zx", > retprobe ? 'r' : 'p', > @@ -10503,7 +10512,8 @@ static inline int add_uprobe_event_legacy(const char *probe_name, bool retprobe, > > static inline int remove_uprobe_event_legacy(const char *probe_name, bool retprobe) > { > - const char *file = "/sys/kernel/debug/tracing/uprobe_events"; > + const char *file = debugfs_available() ? "/sys/kernel/debug/tracing/uprobe_events" : > + "/sys/kernel/tracing/uprobe_events"; > > return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name); > } > @@ -10513,7 +10523,8 @@ static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retpro > char file[512]; > > snprintf(file, sizeof(file), > - "/sys/kernel/debug/tracing/events/%s/%s/id", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > retprobe ? "uretprobes" : "uprobes", probe_name); > > return parse_uint_from_file(file, "%d\n"); > @@ -11071,7 +11082,8 @@ static int determine_tracepoint_id(const char *tp_category, > int ret; > > ret = snprintf(file, sizeof(file), > - "/sys/kernel/debug/tracing/events/%s/%s/id", > + debugfs_available() ? "/sys/kernel/debug/tracing/events/%s/%s/id" : > + "/sys/kernel/tracing/events/%s/%s/id", > tp_category, tp_name); > if (ret < 0) > return -errno; >