Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752038AbdHDK5I (ORCPT ); Fri, 4 Aug 2017 06:57:08 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:55517 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751319AbdHDK5H (ORCPT ); Fri, 4 Aug 2017 06:57:07 -0400 Date: Fri, 4 Aug 2017 12:56:54 +0200 From: Boris Brezillon To: Arnd Bergmann Cc: Andrew Morton , kasan-dev , Dmitry Vyukov , Alexander Potapenko , Andrey Ryabinin , Networking , Linux Kernel Mailing List , Arend van Spriel , David Woodhouse , Brian Norris , Marek Vasut , Richard Weinberger , Cyrille Pitchen , linux-mtd Subject: Re: [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN Message-ID: <20170804125654.2d59e6d5@bbrezillon> In-Reply-To: References: <20170614211556.2062728-1-arnd@arndb.de> <20170614211556.2062728-6-arnd@arndb.de> <20170804094254.369140c0@bbrezillon> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2739 Lines: 54 On Fri, 4 Aug 2017 11:09:53 +0200 Arnd Bergmann wrote: > On Fri, Aug 4, 2017 at 9:42 AM, Boris Brezillon > wrote: > > On Wed, 14 Jun 2017 23:15:40 +0200 > > Arnd Bergmann wrote: > > > >> When CONFIG_KASAN is used, we consume a lot of extra stack space: > >> > >> drivers/mtd/chips/cfi_cmdset_0020.c: In function 'do_write_buffer': > >> drivers/mtd/chips/cfi_cmdset_0020.c:603:1: error: the frame size of 2184 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] > >> drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_erase_varsize': > >> drivers/mtd/chips/cfi_cmdset_0020.c:972:1: error: the frame size of 1936 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] > >> drivers/mtd/chips/cfi_cmdset_0001.c: In function 'do_write_buffer': > >> drivers/mtd/chips/cfi_cmdset_0001.c:1841:1: error: the frame size of 1776 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] > >> > >> This marks some functions as noinline_if_stackbloat to keep reduce the > >> overall stack size. > >> > >> Signed-off-by: Arnd Bergmann > >> --- > >> drivers/mtd/chips/cfi_cmdset_0020.c | 8 ++++---- > >> include/linux/mtd/map.h | 8 ++++---- > >> 2 files changed, 8 insertions(+), 8 deletions(-) > >> > >> diff --git a/drivers/mtd/chips/cfi_cmdset_0020.c b/drivers/mtd/chips/cfi_cmdset_0020.c > >> index 7d342965f392..5eee5e883f55 100644 > >> --- a/drivers/mtd/chips/cfi_cmdset_0020.c > >> +++ b/drivers/mtd/chips/cfi_cmdset_0020.c > >> @@ -244,7 +244,7 @@ static struct mtd_info *cfi_staa_setup(struct map_info *map) > >> } > >> > >> > >> -static inline int do_read_onechip(struct map_info *map, struct flchip *chip, loff_t adr, size_t len, u_char *buf) > >> +static noinline_if_stackbloat int do_read_onechip(struct map_info *map, struct flchip *chip, loff_t adr, size_t len, u_char *buf) > > > > Why do we even need to mark those functions inline in the first place? > > Isn't the compiler smart enough to decide when it should inline things? > > I'm pretty sure it doesn't need the 'inline' keywork. I see that the code was > addedlike this in linux-2.4.0-test3pre3 along with the rest of the mtd layer, > so it has always been 'inline' and nobody ever bothered to remove that > during later cleanups. > > We could probably just mark this function as 'noinline' here and never > inline it, > but I would rather not add more than one variant of noinline_if_stackbloat: > almost all other users of noinline_if_stackbloat are for functions that have > to be inline in normal builds, so it is defined as being either > 'inline' or 'noinline' > depending on whether KASAN is active. Okay. Let's keep it like that then.