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 053A6C433EF for ; Fri, 15 Jul 2022 18:58:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229845AbiGOS6E convert rfc822-to-8bit (ORCPT ); Fri, 15 Jul 2022 14:58:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230050AbiGOS54 (ORCPT ); Fri, 15 Jul 2022 14:57:56 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 172F157209 for ; Fri, 15 Jul 2022 11:57:54 -0700 (PDT) Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 26FGH8FL005538 for ; Fri, 15 Jul 2022 11:57:53 -0700 Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3hae0waxw7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Fri, 15 Jul 2022 11:57:53 -0700 Received: from twshared3657.05.prn5.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.28; Fri, 15 Jul 2022 11:57:52 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 940AC1C635E6A; Fri, 15 Jul 2022 11:57:38 -0700 (PDT) From: Andrii Nakryiko To: , , CC: , , Yonghong Song , Connor O'Brien Subject: [PATCH v2 bpf-next] libbpf: fallback to tracefs mount point if debugfs is not mounted Date: Fri, 15 Jul 2022 11:57:36 -0700 Message-ID: <20220715185736.898848-1-andrii@kernel.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-GUID: S4gK41AXPnOni7uJPLXSGE5OaCR1n3-v X-Proofpoint-ORIG-GUID: S4gK41AXPnOni7uJPLXSGE5OaCR1n3-v X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-15_10,2022-07-15_01,2022-06-22_01 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Teach libbpf to fallback to tracefs mount point (/sys/kernel/tracing) if debugfs (/sys/kernel/debug/tracing) isn't mounted. Acked-by: Yonghong Song Suggested-by: Connor O'Brien Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 61 +++++++++++++++++++++++++++--------------- 1 file changed, 40 insertions(+), 21 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 68da1aca406c..92a775c11e3e 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9828,6 +9828,34 @@ static int append_to_file(const char *file, const char *fmt, ...) return err; } +#define DEBUGFS "/sys/kernel/debug/tracing" +#define TRACEFS "/sys/kernel/tracing" + +static bool use_debugfs(void) +{ + static int has_debugfs = -1; + + if (has_debugfs < 0) + has_debugfs = access(DEBUGFS, F_OK) == 0; + + return has_debugfs == 1; +} + +static const char *tracefs_path(void) +{ + return use_debugfs() ? DEBUGFS : TRACEFS; +} + +static const char *tracefs_kprobe_events(void) +{ + return use_debugfs() ? DEBUGFS"/kprobe_events" : TRACEFS"/kprobe_events"; +} + +static const char *tracefs_uprobe_events(void) +{ + return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events"; +} + static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, const char *kfunc_name, size_t offset) { @@ -9840,9 +9868,7 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz, 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"; - - return append_to_file(file, "%c:%s/%s %s+0x%zx", + return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s+0x%zx", retprobe ? 'r' : 'p', retprobe ? "kretprobes" : "kprobes", probe_name, kfunc_name, offset); @@ -9850,18 +9876,16 @@ 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"; - - return append_to_file(file, "-:%s/%s", retprobe ? "kretprobes" : "kprobes", probe_name); + return append_to_file(tracefs_kprobe_events(), "-:%s/%s", + retprobe ? "kretprobes" : "kprobes", probe_name); } static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retprobe) { char file[256]; - snprintf(file, sizeof(file), - "/sys/kernel/debug/tracing/events/%s/%s/id", - retprobe ? "kretprobes" : "kprobes", probe_name); + snprintf(file, sizeof(file), "%s/events/%s/%s/id", + tracefs_path(), retprobe ? "kretprobes" : "kprobes", probe_name); return parse_uint_from_file(file, "%d\n"); } @@ -10213,9 +10237,7 @@ 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"; - - return append_to_file(file, "%c:%s/%s %s:0x%zx", + return append_to_file(tracefs_uprobe_events(), "%c:%s/%s %s:0x%zx", retprobe ? 'r' : 'p', retprobe ? "uretprobes" : "uprobes", probe_name, binary_path, offset); @@ -10223,18 +10245,16 @@ 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"; - - return append_to_file(file, "-:%s/%s", retprobe ? "uretprobes" : "uprobes", probe_name); + return append_to_file(tracefs_uprobe_events(), "-:%s/%s", + retprobe ? "uretprobes" : "uprobes", probe_name); } static int determine_uprobe_perf_type_legacy(const char *probe_name, bool retprobe) { char file[512]; - snprintf(file, sizeof(file), - "/sys/kernel/debug/tracing/events/%s/%s/id", - retprobe ? "uretprobes" : "uprobes", probe_name); + snprintf(file, sizeof(file), "%s/events/%s/%s/id", + tracefs_path(), retprobe ? "uretprobes" : "uprobes", probe_name); return parse_uint_from_file(file, "%d\n"); } @@ -10782,9 +10802,8 @@ static int determine_tracepoint_id(const char *tp_category, char file[PATH_MAX]; int ret; - ret = snprintf(file, sizeof(file), - "/sys/kernel/debug/tracing/events/%s/%s/id", - tp_category, tp_name); + ret = snprintf(file, sizeof(file), "%s/events/%s/%s/id", + tracefs_path(), tp_category, tp_name); if (ret < 0) return -errno; if (ret >= sizeof(file)) { -- 2.30.2