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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 28C0CC10F13 for ; Sun, 14 Apr 2019 12:45:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E54C82084E for ; Sun, 14 Apr 2019 12:45:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725827AbfDNMpu (ORCPT ); Sun, 14 Apr 2019 08:45:50 -0400 Received: from saturn.retrosnub.co.uk ([46.235.226.198]:46382 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725805AbfDNMpu (ORCPT ); Sun, 14 Apr 2019 08:45:50 -0400 Received: from archlinux (cpc91196-cmbg18-2-0-cust659.5-4.cable.virginm.net [81.96.234.148]) by saturn.retrosnub.co.uk (Postfix; Retrosnub mail submission) with ESMTPSA id CB2F89E6A65; Sun, 14 Apr 2019 13:45:47 +0100 (BST) Date: Sun, 14 Apr 2019 13:45:46 +0100 From: Jonathan Cameron To: Alexandru Ardelean Cc: , Lars-Peter Clausen Subject: Re: [PATCH] iio: ad_sigma_delta: Don't put SPI transfer buffer on the stack Message-ID: <20190414134546.1e9a3907@archlinux> In-Reply-To: <20190409075821.26104-1-alexandru.ardelean@analog.com> References: <20190409075821.26104-1-alexandru.ardelean@analog.com> X-Mailer: Claws Mail 3.17.3 (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-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Tue, 9 Apr 2019 10:58:21 +0300 Alexandru Ardelean wrote: > From: Lars-Peter Clausen > > Use a heap allocated memory for the SPI transfer buffer. Using stack memory > will not work on some architectures when using DMA. > > Signed-off-by: Lars-Peter Clausen > Signed-off-by: Alexandru Ardelean Yikes, surprised this one snuck in here. > --- > > Note: this doesn't need a stable/fixes tag. It's more of an enhancement. Talk me through this... Right now I think this is a bug that is going to cause random and extremely hard to debug problems. I've had these in the past and they are really really nasty as it's random stack corruption. The nasty is not the fact it's on the stack, but the fact that it isn't in it's own cacheline. So my inclination is this definitely needs stable and fixes tag. What am I missing? Jonathan > > drivers/iio/adc/ad_sigma_delta.c | 22 +++++++++++----------- > include/linux/iio/adc/ad_sigma_delta.h | 3 ++- > 2 files changed, 13 insertions(+), 12 deletions(-) > > diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c > index af6cbc683214..02d9049b9218 100644 > --- a/drivers/iio/adc/ad_sigma_delta.c > +++ b/drivers/iio/adc/ad_sigma_delta.c > @@ -58,7 +58,7 @@ EXPORT_SYMBOL_GPL(ad_sd_set_comm); > int ad_sd_write_reg(struct ad_sigma_delta *sigma_delta, unsigned int reg, > unsigned int size, unsigned int val) > { > - uint8_t *data = sigma_delta->data; > + uint8_t *data = sigma_delta->reg_data; > struct spi_transfer t = { > .tx_buf = data, > .len = size + 1, > @@ -102,7 +102,7 @@ EXPORT_SYMBOL_GPL(ad_sd_write_reg); > static int ad_sd_read_reg_raw(struct ad_sigma_delta *sigma_delta, > unsigned int reg, unsigned int size, uint8_t *val) > { > - uint8_t *data = sigma_delta->data; > + uint8_t *data = sigma_delta->reg_data; > int ret; > struct spi_transfer t[] = { > { > @@ -148,24 +148,24 @@ int ad_sd_read_reg(struct ad_sigma_delta *sigma_delta, > { > int ret; > > - ret = ad_sd_read_reg_raw(sigma_delta, reg, size, sigma_delta->data); > + ret = ad_sd_read_reg_raw(sigma_delta, reg, size, sigma_delta->reg_data); > if (ret < 0) > goto out; > > switch (size) { > case 4: > - *val = get_unaligned_be32(sigma_delta->data); > + *val = get_unaligned_be32(sigma_delta->reg_data); > break; > case 3: > - *val = (sigma_delta->data[0] << 16) | > - (sigma_delta->data[1] << 8) | > - sigma_delta->data[2]; > + *val = (sigma_delta->reg_data[0] << 16) | > + (sigma_delta->reg_data[1] << 8) | > + sigma_delta->reg_data[2]; > break; > case 2: > - *val = get_unaligned_be16(sigma_delta->data); > + *val = get_unaligned_be16(sigma_delta->reg_data); > break; > case 1: > - *val = sigma_delta->data[0]; > + *val = sigma_delta->reg_data[0]; > break; > default: > ret = -EINVAL; > @@ -403,12 +403,12 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p) > struct iio_poll_func *pf = p; > struct iio_dev *indio_dev = pf->indio_dev; > struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev); > + uint8_t *data = sigma_delta->buf_data; > unsigned int reg_size; > unsigned int data_reg; > - uint8_t data[16]; > int ret; > > - memset(data, 0x00, 16); > + memset(sigma_delta->buf_data, 0x00, sizeof(sigma_delta->buf_data)); > > reg_size = indio_dev->channels[0].scan_type.realbits + > indio_dev->channels[0].scan_type.shift; > diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h > index 6e9fb1932dde..fb77b2ebe498 100644 > --- a/include/linux/iio/adc/ad_sigma_delta.h > +++ b/include/linux/iio/adc/ad_sigma_delta.h > @@ -79,7 +79,8 @@ struct ad_sigma_delta { > * DMA (thus cache coherency maintenance) requires the > * transfer buffers to live in their own cache lines. > */ > - uint8_t data[4] ____cacheline_aligned; > + uint8_t reg_data[4] ____cacheline_aligned; > + uint8_t buf_data[16]; > }; > > static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,