From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C31AD37F8AC; Fri, 22 May 2026 14:45:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779461103; cv=none; b=on4EIWCi1fv0Xu6Ml2GLcX8dlYyZQyTb2a1f44sp5/j/f++yOZigqYSYNVPn2PVzDYRGkz1ZO2Co3YT/ogKOmTJDdaF3ne+MlUT7OEWvpyVEOBmWhYa5lFcGgXrrgHnf77DFnCVkWIMyha5Xdw2cCESf0ZniwZ6I9clKn6sk4Vk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779461103; c=relaxed/simple; bh=CdLEo+ax1C9GSpVzhZDopuh9TX3AWdjXHO9wbDfoM6k=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=XhiU99M6suYUiOTUEDDnbRPugTCJL6JnQdZOQPewtUSoNytubhjHcWD3OwjJ0svP/BNyi64hqGyJ7xz7ozTl/0L7dJkASbZMZnyJaSiJ9OjzflL9iofbYnvgCf21o/ZMiMi0yNuUL9VqWD4oseZA6WEY92SRDSqwFpzPhfO4eYo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A6KiomUF; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A6KiomUF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF0391F000E9; Fri, 22 May 2026 14:44:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779461100; bh=MH216XXgrREg/PBBIQe92jArAeQbIbepqZdPmraWA5g=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=A6KiomUFdxRMqA5XHWbscp/Kx2YUwVdETQWDXYl/GrIA8Dznwo/6TG9TBLhR7mBeO 8GWhuERm7oOkVMPMI45Z3OH6GvNvZujbtGes1/kqfY/IWiiBmjxoQa9clNGRrDedUQ MxJmhC0YKXwxyy0VjTDbs18S4nLMPr0ZAJ9xQ5jMKidww79a+xmiKx4kOEMWCO1Knl 0Mw1qvUg23vZ7cS6MzAlQaWXgsSDFGIKGcTg3D/JGmOTq/BHfd5WYaS3xYLYaiPgvT 0WaPS6+q2O1nXGN2tTwBGS7JZjnVCieNb7jNOF1Mfk9Z5IEM31RF9he957IB+qfUuG bk5XtanY9OOHA== Date: Fri, 22 May 2026 10:45:21 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: LKML , Linux trace kernel , Mathieu Desnoyers , Mark Rutland , Peter Zijlstra , Namhyung Kim , Takaya Saeki , Douglas Raillard , Tom Zanussi , Andrew Morton , Thomas Gleixner , Ian Rogers , Jiri Olsa , "sashiko-bot@kernel.org" , "sashiko-reviews@lists.linux.dev" Subject: Re: [PATCH v6] tracing/eprobes: Allow use of BTF names to dereference pointers Message-ID: <20260522104521.74981686@gandalf.local.home> In-Reply-To: <20260522072322.18aa72dd@gandalf.local.home> References: <20260521225033.56458336@fedora> <20260522072322.18aa72dd@gandalf.local.home> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 22 May 2026 07:23:22 -0400 Steven Rostedt wrote: > > > @@ -653,6 +686,20 @@ static int parse_btf_arg(char *varname, > > > return -EOPNOTSUPP; > > > } > > > > > > + if (ctx->flags & TPARG_FL_TEVENT) { > > > + int ret; > > > + > > > + ret = parse_trace_event(varname, code, ctx); > > > + if (ret < 0) > > > + return ret; > > > When parse_trace_event() returns a negative error code (such as -EINVAL or > > -ENOENT) because a field name is invalid, the error is propagated back up > > the stack. Does this path miss calling trace_probe_log_err()? > > If so, users might receive a generic failure without context or a caret > > pointing to the specific syntax error. > > Hmm, there's a comment in the parse_trace_event() that sets ctx->offset for > backward compatibility. I'll investigate to see if we can fix that now. Masami, I looked at the code for parse_trace_event() that has: /* backward compatibility */ ctx->offset = 0; return -EINVAL; And it was originally introduced by commit 1b8b0cd754cd ("tracing/probes: Move event parameter fetching code to common parser"), with: + ret = parse_trace_event_arg(arg, code, ctx); + if (!ret) + return 0; + if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) { + code->op = FETCH_OP_COMM; + return 0; + } + /* backward compatibility */ + ctx->offset = 0; + goto inval; + } + What was the reason for the "backward compatibility"? Can we make it a real error now? -- Steve