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 9F801C10F04 for ; Fri, 1 Dec 2023 00:27:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377417AbjLAAZd convert rfc822-to-8bit (ORCPT ); Thu, 30 Nov 2023 19:25:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377389AbjLAAZb (ORCPT ); Thu, 30 Nov 2023 19:25:31 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98E62197 for ; Thu, 30 Nov 2023 16:25:35 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3096DC433C8; Fri, 1 Dec 2023 00:25:33 +0000 (UTC) Date: Thu, 30 Nov 2023 19:25:54 -0500 From: Steven Rostedt To: =?UTF-8?B?xYF1a2Fzeg==?= Bartosik Cc: Jason Baron , Jim Cromie , Andrew Morton , Kees Cook , Douglas Anderson , Guenter Roeck , Yaniv Tzoreff , Benson Leung , Vincent Whitchurch , Pekka Paalanen , Sean Paul , Daniel Vetter , linux-kernel@vger.kernel.org, upstream@semihalf.com, pmladek@suse.com, sergey.senozhatsky@gmail.com, john.ogness@linutronix.de, Simon Ser Subject: Re: [PATCH v2 05/15] tracefs: add __get_str_strip_nl - RFC Message-ID: <20231130192554.10da680c@gandalf.local.home> In-Reply-To: <20231130234048.157509-6-lb@semihalf.com> References: <20231130234048.157509-1-lb@semihalf.com> <20231130234048.157509-6-lb@semihalf.com> X-Mailer: Claws Mail 3.19.1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 1 Dec 2023 00:40:38 +0100 Łukasz Bartosik wrote: > From: Jim Cromie > > This variant of __get_str() removes the trailing newline. It is for > use by printk/debug-ish events which already have a trailing newline. > It is here to support: > > https://lore.kernel.org/lkml/ > 20200825153338.17061-1-vincent.whitchurch@axis.com/ Line wrap breakage. > which taught dyndbg to send pr_debug() msgs to tracefs, via -x/T flag. > > It "reused" the include/trace/events/printk.h console event, > which does the following: > > TP_fast_assign( > /* > * Each trace entry is printed in a new line. > * If the msg finishes with '\n', cut it off > * to avoid blank lines in the trace. > */ > if (len > 0 && (msg[len-1] == '\n')) > len -= 1; > > memcpy(__get_str(s), msg, len); > __get_str(s)[len] = 0; > ), > > That trim work could be avoided, *if* all pr_debug() callers are > known to have no '\n' to strip. While that's not true for *all* > callsites, it is 99+% true for DRM.debug callsites, and can be made > true for some subsets of prdbg/dyndbg callsites. > > WANTED: macros to validate that a literal format-str has or doesn't > have a trailing newline, or to provide or trim trailing newline(s?). > Should be usable in TP_printk* defns, for use in new event defns. > > Cc: > Cc: Vincent Whitchurch > Cc: > Cc: > Cc: > Cc: > Cc: Simon Ser > Cc: Sean Paul > Signed-off-by: Jim Cromie > Signed-off-by: Łukasz Bartosik > --- > include/trace/stages/stage3_trace_output.h | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/include/trace/stages/stage3_trace_output.h b/include/trace/stages/stage3_trace_output.h > index c1fb1355d309..92a79bd5c0cd 100644 > --- a/include/trace/stages/stage3_trace_output.h > +++ b/include/trace/stages/stage3_trace_output.h > @@ -19,6 +19,15 @@ > #undef __get_str > #define __get_str(field) ((char *)__get_dynamic_array(field)) > > +#undef __get_str_strip_nl > +#define __get_str_strip_nl(field) \ > + ({ \ > + char *s = __get_str(field); \ > + size_t len = strlen(s); \ > + if (len && s[len-1] == '\n') \ > + s[len-1] = '\0'; s; \ > + }) I'd be worried about modifying the string itself as you are doing above. That's modifying the source which may have unintended consequences. That said, there's a trace_seq that is available for stage 3 called "p". You can use that: #define __get_str_strip_nl(field) \ ({ \ char *s = trace_seq_buffer_ptr(p); \ size_t len; \ trace_seq_printf(p, "%s", __get_str(field)); \ trace_seq_putc(p, '\0'); \ len = strlen(s); \ if (len && s[len-1] == '\n') \ s[len-1] = '\0'; \ s; \ }) -- Steve > + > #undef __get_rel_dynamic_array > #define __get_rel_dynamic_array(field) \ > ((void *)__entry + \