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 F1325C001DE for ; Tue, 18 Jul 2023 00:00:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229939AbjGRAAk (ORCPT ); Mon, 17 Jul 2023 20:00:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35502 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230159AbjGRAAi (ORCPT ); Mon, 17 Jul 2023 20:00:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD506EC; Mon, 17 Jul 2023 17:00:36 -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 732D16135C; Tue, 18 Jul 2023 00:00:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5D72C433C8; Tue, 18 Jul 2023 00:00:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689638435; bh=qcUEcDK6AXqP07t5ytqWFHjiJgDcpFUrQBIZzSKb7T8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TUIFBBNxwYgVURjg535s2o1fErHH/q+Ig56Bb9E+GJ8H8bPrCtcvtFIDe/M9dU2mg 6ITNePUfFTvCVJL0UmOE6hX3kF0LUR2iiveh7H/mE0/crh/4Y3zzhBCSGVUGl/V8Xb dseXrP5zHr7HMpQbJ/D4Aw4yg5ElIZjX2ckhQm46+nuI6t6Q9fBhv0ZA+uSaJ6NRhD 2R9YyEP2xiq3K6CPV9Ks+UIFgt/w3pHxJ17rNHSYbECUf4y2REFFrqlmBZxTxNyq7O 76hvgC6I7Yzvy/3PXsemqk/gUUA8Rkl31AtGwsZt1inZ3o/DeCYQcnk9GszZcyYtT3 kXtSLEFqTY0qQ== Date: Tue, 18 Jul 2023 09:00:33 +0900 From: Masami Hiramatsu (Google) To: Steven Rostedt Cc: Linux Trace Kernel , LKML , Masami Hiramatsu , Mark Rutland Subject: Re: [PATCH] tracing/probes: Differentiate BTF support from start of function Message-Id: <20230718090033.5f4d0a7df2657b0cc71f9219@kernel.org> In-Reply-To: <20230717163947.4969316a@gandalf.local.home> References: <20230717163947.4969316a@gandalf.local.home> X-Mailer: Sylpheed 3.8.0beta1 (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-kernel@vger.kernel.org On Mon, 17 Jul 2023 16:39:47 -0400 Steven Rostedt wrote: > From: "Steven Rostedt (Google)" > > Having a typo in the function name to trace one of the arguments using > BTF, gave me an error message that BTF was not supported by this kernel: > > ~# echo 'p:lock __raw_spin_lock lock=lock' > /sys/kernel/tracing/kprobe_events > -bash: echo: write error: Invalid argument > ~# cat /sys/kernel/tracing/error_log > [ 34.382149] trace_kprobe: error: BTF is not available or not supported > Command: p:lock __raw_spin_lock lock=lock > ^ > > I added two underscores instead of one underscore for the function > _raw_spin_lock(). But I spent too much time trying to figure out why BTF > was not supported, because in reality it was! The problem was that the > function wasn't found (this could happen if a function offset is used as > well). Thanks for reporting! > > Instead, add a new error message that gives a better description of the > problem. > > ~# echo 'p:lock __raw_spin_lock lock=lock' > /sys/kernel/tracing/kprobe_events > -bash: echo: write error: Invalid argument > ~# cat /sys/kernel/tracing/error_log > [ 45.922742] trace_kprobe: error: BTF arg can be used only on function entry > Command: p:lock __raw_spin_lock lock=lock > ^ This looks good to me. Acked-by: Masami Hiramatsu (Google) Thank you! > Fixes: b576e09701c7d ("tracing/probes: Support function parameters if BTF is available") > Signed-off-by: Steven Rostedt (Google) > --- > kernel/trace/trace_probe.c | 2 +- > kernel/trace/trace_probe.h | 1 + > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > index cf504efd0694..328a51b1d068 100644 > --- a/kernel/trace/trace_probe.c > +++ b/kernel/trace/trace_probe.c > @@ -1023,7 +1023,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type, > default: > if (isalpha(arg[0]) || arg[0] == '_') { /* BTF variable */ > if (!tparg_is_function_entry(ctx->flags)) { > - trace_probe_log_err(ctx->offset, NOSUP_BTFARG); > + trace_probe_log_err(ctx->offset, NOFENTRY_BTFARG); > return -EINVAL; > } > ret = parse_btf_arg(arg, pcode, end, ctx); > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h > index 604d6fb9c5ff..554fe2995ca1 100644 > --- a/kernel/trace/trace_probe.h > +++ b/kernel/trace/trace_probe.h > @@ -493,6 +493,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, > C(BAD_ATTACH_ARG, "Attached event does not have this field"),\ > C(NO_EP_FILTER, "No filter rule after 'if'"), \ > C(NOSUP_BTFARG, "BTF is not available or not supported"), \ > + C(NOFENTRY_BTFARG, "BTF arg can be used only on function entry"), \ > C(NO_BTFARG, "This variable is not found at this probe point"),\ > C(NO_BTF_ENTRY, "No BTF entry for this probe point"), \ > C(BAD_VAR_ARGS, "$arg* must be an independent parameter without name etc."),\ > -- > 2.40.1 > -- Masami Hiramatsu (Google)