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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D695C38A2A for ; Thu, 7 May 2020 10:25:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D00A208E4 for ; Thu, 7 May 2020 10:25:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726579AbgEGKZF (ORCPT ); Thu, 7 May 2020 06:25:05 -0400 Received: from relay10.mail.gandi.net ([217.70.178.230]:50055 "EHLO relay10.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbgEGKZF (ORCPT ); Thu, 7 May 2020 06:25:05 -0400 Received: from xps13 (unknown [91.224.148.103]) (Authenticated sender: miquel.raynal@bootlin.com) by relay10.mail.gandi.net (Postfix) with ESMTPSA id 831E6240014; Thu, 7 May 2020 10:21:11 +0000 (UTC) Date: Thu, 7 May 2020 12:21:10 +0200 From: Miquel Raynal To: Nathan Chancellor Cc: Arnd Bergmann , Richard Weinberger , Vignesh Raghavendra , Vincenzo Aliberti , Brian Norris , Richard Fontana , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: [PATCH] mtd: lpddr: fix excessive stack usage with clang Message-ID: <20200507122110.50ccce48@xps13> In-Reply-To: <20200506023828.GA415100@ubuntu-s3-xlarge-x86> References: <20200505140136.263461-1-arnd@arndb.de> <20200506023828.GA415100@ubuntu-s3-xlarge-x86> Organization: Bootlin X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nathan Chancellor wrote on Tue, 5 May 2020 19:38:28 -0700: > On Tue, May 05, 2020 at 04:01:16PM +0200, Arnd Bergmann wrote: > > Building lpddr2_nvm with clang can result in a giant stack usage > > in one function: > > > > drivers/mtd/lpddr/lpddr2_nvm.c:399:12: error: stack frame size of 1144 bytes in function 'lpddr2_nvm_probe' [-Werror,-Wframe-larger-than=] > > > > The problem is that clang decides to build a copy of the mtd_info > > structure on the stack and then do a memcpy() into the actual version. It > > shouldn't really do it that way, but it's not strictly a bug either. > > > > As a workaround, use a static const version of the structure to assign > > most of the members upfront and then only set the few members that > > require runtime knowledge at probe time. > > > > Fixes: 96ba9dd65788 ("mtd: lpddr: add driver for LPDDR2-NVM PCM memories") > > Signed-off-by: Arnd Bergmann > > Reviewed-by: Nathan Chancellor Acked-by: Miquel Raynal > > > --- > > drivers/mtd/lpddr/lpddr2_nvm.c | 35 ++++++++++++++++++---------------- > > 1 file changed, 19 insertions(+), 16 deletions(-) > > > > diff --git a/drivers/mtd/lpddr/lpddr2_nvm.c b/drivers/mtd/lpddr/lpddr2_nvm.c > > index 0f1547f09d08..72f5c7b30079 100644 > > --- a/drivers/mtd/lpddr/lpddr2_nvm.c > > +++ b/drivers/mtd/lpddr/lpddr2_nvm.c > > @@ -393,6 +393,17 @@ static int lpddr2_nvm_lock(struct mtd_info *mtd, loff_t start_add, > > return lpddr2_nvm_do_block_op(mtd, start_add, len, LPDDR2_NVM_LOCK); > > } > > > > +static const struct mtd_info lpddr2_nvm_mtd_info = { > > + .type = MTD_RAM, > > + .writesize = 1, > > + .flags = (MTD_CAP_NVRAM | MTD_POWERUP_LOCK), > > + ._read = lpddr2_nvm_read, > > + ._write = lpddr2_nvm_write, > > + ._erase = lpddr2_nvm_erase, > > + ._unlock = lpddr2_nvm_unlock, > > + ._lock = lpddr2_nvm_lock, > > +}; > > + > > /* > > * lpddr2_nvm driver probe method > > */ > > @@ -433,6 +444,7 @@ static int lpddr2_nvm_probe(struct platform_device *pdev) > > .pfow_base = OW_BASE_ADDRESS, > > .fldrv_priv = pcm_data, > > }; > > + > > if (IS_ERR(map->virt)) > > return PTR_ERR(map->virt); > > > > @@ -444,22 +456,13 @@ static int lpddr2_nvm_probe(struct platform_device *pdev) > > return PTR_ERR(pcm_data->ctl_regs); > > > > /* Populate mtd_info data structure */ > > - *mtd = (struct mtd_info) { > > - .dev = { .parent = &pdev->dev }, > > - .name = pdev->dev.init_name, > > - .type = MTD_RAM, > > - .priv = map, > > - .size = resource_size(add_range), > > - .erasesize = ERASE_BLOCKSIZE * pcm_data->bus_width, > > - .writesize = 1, > > - .writebufsize = WRITE_BUFFSIZE * pcm_data->bus_width, > > - .flags = (MTD_CAP_NVRAM | MTD_POWERUP_LOCK), > > - ._read = lpddr2_nvm_read, > > - ._write = lpddr2_nvm_write, > > - ._erase = lpddr2_nvm_erase, > > - ._unlock = lpddr2_nvm_unlock, > > - ._lock = lpddr2_nvm_lock, > > - }; > > + *mtd = lpddr2_nvm_mtd_info; > > + mtd->dev.parent = &pdev->dev; > > + mtd->name = pdev->dev.init_name; > > + mtd->priv = map; > > + mtd->size = resource_size(add_range); > > + mtd->erasesize = ERASE_BLOCKSIZE * pcm_data->bus_width; > > + mtd->writebufsize = WRITE_BUFFSIZE * pcm_data->bus_width; > > > > /* Verify the presence of the device looking for PFOW string */ > > if (!lpddr2_nvm_pfow_present(map)) { > > -- > > 2.26.0 > >