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Tue, 22 Jun 2021 09:43:51 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 2581E214D35; Tue, 22 Jun 2021 09:43:51 +0200 (CEST) Received: from lmecxl0889.lme.st.com (10.75.127.46) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 22 Jun 2021 09:43:50 +0200 Subject: Re: [PATCH v2 1/1] rpmsg: ctrl: Introduce new RPMSG_CREATE/RELEASE_DEV_IOCTL controls To: Mathieu Poirier CC: Bjorn Andersson , Ohad Ben-Cohen , , , References: <20210621125800.27696-1-arnaud.pouliquen@foss.st.com> <20210621125800.27696-2-arnaud.pouliquen@foss.st.com> <20210621231633.GC980846@p14s> From: Arnaud POULIQUEN Message-ID: <343c372e-0c0a-ad4e-356b-47eb975ce0e0@foss.st.com> Date: Tue, 22 Jun 2021 09:43:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210621231633.GC980846@p14s> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.46] X-ClientProxiedBy: SFHDAG1NODE3.st.com (10.75.127.3) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-06-22_04:2021-06-21,2021-06-22 signatures=0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mathieu On 6/22/21 1:16 AM, Mathieu Poirier wrote: > On Mon, Jun 21, 2021 at 02:58:00PM +0200, Arnaud Pouliquen wrote: >> Allow the user space application to create and release an rpmsg device >> by adding RPMSG_CREATE_DEV_IOCTL and RPMSG_RELEASE_DEV_IOCTL ioctrls to >> the /dev/rpmsg_ctrl interface >> >> The RPMSG_CREATE_DEV_IOCTL Ioctl can be used to instantiate a local rpmsg >> device. >> Depending on the back-end implementation, the associated rpmsg driver is >> probed and a NS announcement can be sent to the remote processor. >> >> The RPMSG_RELEASE_DEV_IOCTL allows the user application to release a >> rpmsg device created either by the remote processor or with the >> RPMSG_CREATE_DEV_IOCTL call. >> Depending on the back-end implementation, the associated rpmsg driver is >> removed and a NS destroy rpmsg can be sent to the remote processor. >> >> Suggested-by: Mathieu Poirier >> Signed-off-by: Arnaud Pouliquen >> --- >> drivers/rpmsg/rpmsg_ctrl.c | 37 +++++++++++++++++++++++++++++++++---- >> include/uapi/linux/rpmsg.h | 10 ++++++++++ >> 2 files changed, 43 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c >> index eeb1708548c1..cb19e32d05e1 100644 >> --- a/drivers/rpmsg/rpmsg_ctrl.c >> +++ b/drivers/rpmsg/rpmsg_ctrl.c >> @@ -23,6 +23,7 @@ >> #include >> >> #include "rpmsg_char.h" >> +#include "rpmsg_internal.h" >> >> static dev_t rpmsg_major; >> >> @@ -37,11 +38,13 @@ static DEFINE_IDA(rpmsg_minor_ida); >> * @rpdev: underlaying rpmsg device >> * @cdev: cdev for the ctrl device >> * @dev: device for the ctrl device >> + * @ctrl_lock: serialize the ioctrls. >> */ >> struct rpmsg_ctrldev { >> struct rpmsg_device *rpdev; >> struct cdev cdev; >> struct device dev; >> + struct mutex ctrl_lock; >> }; >> >> static int rpmsg_ctrldev_open(struct inode *inode, struct file *filp) >> @@ -70,9 +73,8 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd, >> void __user *argp = (void __user *)arg; >> struct rpmsg_endpoint_info eptinfo; >> struct rpmsg_channel_info chinfo; >> - >> - if (cmd != RPMSG_CREATE_EPT_IOCTL) >> - return -EINVAL; >> + struct rpmsg_device *rpdev; >> + int ret = 0; >> >> if (copy_from_user(&eptinfo, argp, sizeof(eptinfo))) >> return -EFAULT; >> @@ -82,7 +84,33 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd, >> chinfo.src = eptinfo.src; >> chinfo.dst = eptinfo.dst; >> >> - return rpmsg_chrdev_eptdev_create(ctrldev->rpdev, &ctrldev->dev, chinfo); >> + mutex_lock(&ctrldev->ctrl_lock); > > Have you been able to verify the VFS layer doesn't take care of serializing > ioctl() and file accesses in general? I did a quick search in the drivers/ > directory and the vast majority of implementations don't use a lock. Please find my answer here https://lkml.org/lkml/2021/6/21/235 I tested by suppressing the lock and adding msleep to check a potential atomic. in the rpmsg_ctrldev_ioctl function. Nothing seems prevent the re-entrance. Regards, Arnaud > > Thanks, > Mathieu > >> + switch (cmd) { >> + case RPMSG_CREATE_EPT_IOCTL: >> + ret = rpmsg_chrdev_eptdev_create(ctrldev->rpdev, &ctrldev->dev, chinfo); >> + break; >> + >> + case RPMSG_CREATE_DEV_IOCTL: >> + rpdev = rpmsg_create_channel(ctrldev->rpdev, &chinfo); >> + if (!rpdev) { >> + dev_err(&ctrldev->dev, "failed to create %s channel\n", chinfo.name); >> + ret = -ENXIO; >> + } >> + break; >> + >> + case RPMSG_RELEASE_DEV_IOCTL: >> + ret = rpmsg_release_channel(ctrldev->rpdev, &chinfo); >> + if (ret) >> + dev_err(&ctrldev->dev, "failed to release %s channel (%d)\n", >> + chinfo.name, ret); >> + break; >> + >> + default: >> + ret = -EINVAL; >> + } >> + mutex_unlock(&ctrldev->ctrl_lock); >> + >> + return ret; >> }; >> >> static const struct file_operations rpmsg_ctrldev_fops = { >> @@ -119,6 +147,7 @@ static int rpmsg_ctrldev_probe(struct rpmsg_device *rpdev) >> device_initialize(dev); >> dev->parent = &rpdev->dev; >> >> + mutex_init(&ctrldev->ctrl_lock); >> cdev_init(&ctrldev->cdev, &rpmsg_ctrldev_fops); >> ctrldev->cdev.owner = THIS_MODULE; >> >> diff --git a/include/uapi/linux/rpmsg.h b/include/uapi/linux/rpmsg.h >> index f5ca8740f3fb..1637e68177d9 100644 >> --- a/include/uapi/linux/rpmsg.h >> +++ b/include/uapi/linux/rpmsg.h >> @@ -33,4 +33,14 @@ struct rpmsg_endpoint_info { >> */ >> #define RPMSG_DESTROY_EPT_IOCTL _IO(0xb5, 0x2) >> >> +/** >> + * Instantiate a new local rpmsg service device. >> + */ >> +#define RPMSG_CREATE_DEV_IOCTL _IOW(0xb5, 0x3, struct rpmsg_endpoint_info) >> + >> +/** >> + * Release a local rpmsg device. >> + */ >> +#define RPMSG_RELEASE_DEV_IOCTL _IOW(0xb5, 0x4, struct rpmsg_endpoint_info) >> + >> #endif >> -- >> 2.17.1 >>