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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 9FFB1C4338F for ; Thu, 12 Aug 2021 09:26:39 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9259A6056B for ; Thu, 12 Aug 2021 09:26:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9259A6056B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 93D816E3AA; Thu, 12 Aug 2021 09:26:37 +0000 (UTC) Received: from netline-mail3.netline.ch (mail.netline.ch [148.251.143.180]) by gabe.freedesktop.org (Postfix) with ESMTP id A41CB6E3AA for ; Thu, 12 Aug 2021 09:26:35 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id D23AC20201B; Thu, 12 Aug 2021 11:26:34 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id TkZ1FcLJEcwf; Thu, 12 Aug 2021 11:26:30 +0200 (CEST) Received: from thor (24.99.2.85.dynamic.wline.res.cust.swisscom.ch [85.2.99.24]) by netline-mail3.netline.ch (Postfix) with ESMTPA id 5295820201A; Thu, 12 Aug 2021 11:26:30 +0200 (CEST) Received: from localhost ([::1]) by thor with esmtp (Exim 4.94.2) (envelope-from ) id 1mE6yq-0001ax-Tb; Thu, 12 Aug 2021 11:26:28 +0200 To: Mark Yacoub , seanpaul@chromium.org, abhinavk@codeaurora.org, robdclark@chromium.org, irlied@linux.ie, dri-devel@lists.freedesktop.org Cc: Mark Yacoub References: <20210811175525.2125964-1-markyacoub@chromium.org> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Subject: Re: [PATCH] drm: Copy drm_wait_vblank request and copy_to_user before return. Message-ID: Date: Thu, 12 Aug 2021 11:26:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210811175525.2125964-1-markyacoub@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-CA Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 2021-08-11 7:55 p.m., Mark Yacoub wrote: > From: Mark Yacoub > > [Why] > Userspace should get back a copy of the request that's been modified > even when drm_wait_vblank_ioctl returns a failure. > > Rationale: > drm_wait_vblank_ioctl modifies the request and expects the user to read > back. When the type is RELATIVE, it modifies it to ABSOLUTE and updates > the sequence to become current_vblank_count + sequence (which was > relative), not it becomes absolute. > drmWaitVBlank (in libdrm), expects this to be the case as it modifies > the request to be Absolute as it expects the sequence to would have been > updated. > > The change is in compat_drm_wait_vblank, which is called by > drm_compat_ioctl. This change of copying the data back regardless of the > return number makes it en par with drm_ioctl, which always copies the > data before returning. > > [How] > Copy the drm_wait_vblank request. > Return from the function after everything has been copied to user. > > Fixes: IGT:kms_flip::modeset-vs-vblank-race-interruptible > Tested on ChromeOS Trogdor(msm) > > Signed-off-by: Mark Yacoub > --- > drivers/gpu/drm/drm_ioc32.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c > index d29907955ff79..275b860df8fbe 100644 > --- a/drivers/gpu/drm/drm_ioc32.c > +++ b/drivers/gpu/drm/drm_ioc32.c > @@ -855,17 +855,19 @@ static int compat_drm_wait_vblank(struct file *file, unsigned int cmd, > req.request.sequence = req32.request.sequence; > req.request.signal = req32.request.signal; > err = drm_ioctl_kernel(file, drm_wait_vblank_ioctl, &req, DRM_UNLOCKED); > - if (err) > - return err; > > req32.reply.type = req.reply.type; > req32.reply.sequence = req.reply.sequence; > req32.reply.tval_sec = req.reply.tval_sec; > req32.reply.tval_usec = req.reply.tval_usec; > + /* drm_wait_vblank_ioctl modifies Request, update their values here as well. */ > + req32.request.type = req.request.type; > + req32.request.sequence = req.request.sequence; > + req32.request.signal = req.request.signal; The added assignments are superfluous, since req32.reply and req32.request are members of the same union. > if (copy_to_user(argp, &req32, sizeof(req32))) > return -EFAULT; > > - return 0; > + return err; > } The other changes look correct. -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and X developer