Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752562AbdFNWQu (ORCPT ); Wed, 14 Jun 2017 18:16:50 -0400 Received: from hera.aquilenet.fr ([141.255.128.1]:37842 "EHLO hera.aquilenet.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751606AbdFNWQs (ORCPT ); Wed, 14 Jun 2017 18:16:48 -0400 Date: Thu, 15 Jun 2017 00:16:44 +0200 From: Samuel Thibault To: Arnd Bergmann Cc: Andrew Morton , kasan-dev , Dmitry Vyukov , Alexander Potapenko , Andrey Ryabinin , Networking , Linux Kernel Mailing List , Arend van Spriel , Greg Kroah-Hartman , Jiri Slaby , Dmitry Torokhov Subject: Re: [PATCH v2 03/11] tty: kbd: reduce stack size with KASAN Message-ID: <20170614221644.sws7xgm5cgiia6oo@var.youpi.perso.aquilenet.fr> Mail-Followup-To: Samuel Thibault , Arnd Bergmann , Andrew Morton , kasan-dev , Dmitry Vyukov , Alexander Potapenko , Andrey Ryabinin , Networking , Linux Kernel Mailing List , Arend van Spriel , Greg Kroah-Hartman , Jiri Slaby , Dmitry Torokhov References: <20170614211556.2062728-1-arnd@arndb.de> <20170614211556.2062728-4-arnd@arndb.de> <20170614212834.mtmq3wlnq525qkiz@var.youpi.perso.aquilenet.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: I am not organized User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1489 Lines: 33 Arnd Bergmann, on mer. 14 juin 2017 23:56:39 +0200, wrote: > > I however agree that it's a bad idea to inline it in functions where > > it's called so many times (and we're talking about the keyboard anyway). > > > >> -static void puts_queue(struct vc_data *vc, char *cp) > >> +static noinline_if_stackbloat void puts_queue(struct vc_data *vc, char *cp) > > > > I don't see why, it's only called once in the callers. k_fn, however, is > > called several times in k_pad, so that could be why, but then it's > > rather be the inlining of k_fn which is a bad idea. > > It's called by applkey, which in turn is called by k_pad(), k_pad calls applkey twice only. Is that really to be considered bloat? > >> -static void fn_send_intr(struct vc_data *vc) > >> +static noinline_if_stackbloat void fn_send_intr(struct vc_data *vc) > > > > This one is only referenced, not called, I don't see how that could pose > > problem. > > I was surprised by this as well, but it seems that gcc these days is > smart enough to turn the indirect function calls for k_handler[type] > and/or f_handler[value] into inlines again when it has already > determined the index to be constant. Cool :) But I don't see how it can see find it out constant. The only fn_handler[] caller is k_spec, using value as index. The only caller of f_handler[] is kbd_keycode, using type as index, and keysym&0xff as value. That is definitely not constant :) And it's only one caller, I don't see how that can bloat. Samuel