From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 06ECF6FB0; Thu, 18 Apr 2024 14:51:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713451884; cv=none; b=PuFSepq1SbDIft6l5ir7aXDghCLsDT7EE79dRZ/R9ySBVzqryrWV9IOGOvcaNf1mnp21n+BOgft4JGOTT+Npcoqn1UWYd7rSsLQKVJQ2z4wpqfu82zAXNv2OK8UU20fPo9xx5FpFxi0wOPCBuyqjs+tq1mSkPvD6SHpiEfxRoD8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713451884; c=relaxed/simple; bh=otmv7rhTIoDeXBnEHe3n9sVC/BWFho4XCMjhnjOJ0+Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CMXekI/Nidq4t9ZPB/GeyLWDcGT42BBCe9oFSFT7EuXupFXjjUsbxWSv8pJYhlOcKsalCKrvYt13pbEDFocUIrI6P+rNBI/3jE2/VGOXnmQBhEEZssPZ/FBcBmGxwV+bfGuwkZBfsxBaCHwNd+lwy3Eg7M5h74vmNMji2HynzCM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=avA3AfO6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="avA3AfO6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C484EC113CC; Thu, 18 Apr 2024 14:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713451883; bh=otmv7rhTIoDeXBnEHe3n9sVC/BWFho4XCMjhnjOJ0+Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=avA3AfO64KbySRBK0fRSPMK17uPXHs9lfqpO90wMXiMWbY7s5mnV+P8rgY5k7ENAK Xv60/ZO+V1h/qeOC4YUUtmXpB2J8uUO03pxEN8EwrwxW5a9No9NmCGGY8Rl0O79b6k 0esWC8IBeJLIhoruXD3DXC/cfCSGeebWzOX/5nAn46R2bSdn/HVbetRfZzsrgoraiV wviU4W75cgzee/E4jb34DhKClrhLi9+atKpwcZb5XBwfRZe9d9Re+LSHuQ9uPQKaoG CkhEHxddN+vfu1tqBtIJuhsGpkKgJhCOChKFQxBHE+6m2WMuO/GFoWgWmT7agaBFM7 eAMo+6+adpVgQ== Date: Thu, 18 Apr 2024 07:51:21 -0700 From: Nathan Chancellor To: Heiko Carstens Cc: akpm@linux-foundation.org, arnd@arndb.de, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, wintera@linux.ibm.com, twinkler@linux.ibm.com, linux-s390@vger.kernel.org, netdev@vger.kernel.org, llvm@lists.linux.dev, patches@lists.linux.dev Subject: Re: [PATCH 1/3] s390/vmlogrdr: Remove function pointer cast Message-ID: <20240418145121.GA1435416@dev-arch.thelio-3990X> References: <20240417-s390-drivers-fix-cast-function-type-v1-0-fd048c9903b0@kernel.org> <20240417-s390-drivers-fix-cast-function-type-v1-1-fd048c9903b0@kernel.org> <20240418095438.6056-A-hca@linux.ibm.com> <20240418102549.6056-B-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240418102549.6056-B-hca@linux.ibm.com> Hi Heiko, On Thu, Apr 18, 2024 at 12:25:49PM +0200, Heiko Carstens wrote: > On Thu, Apr 18, 2024 at 11:54:38AM +0200, Heiko Carstens wrote: > > On Wed, Apr 17, 2024 at 11:24:35AM -0700, Nathan Chancellor wrote: > > > Clang warns (or errors with CONFIG_WERROR) after enabling > > > -Wcast-function-type-strict by default: > > > > > > drivers/s390/char/vmlogrdr.c:746:18: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict] > > > 746 | dev->release = (void (*)(struct device *))kfree; > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > 1 error generated. > > > > > > Add a standalone function to fix the warning properly, which addresses > > > the root of the warning that these casts are not safe for kCFI. The > > > comment is not really relevant after this change, so remove it. > > > > > > Signed-off-by: Nathan Chancellor > > > --- > > > drivers/s390/char/vmlogrdr.c | 13 +++++-------- > > > 1 file changed, 5 insertions(+), 8 deletions(-) > > > > > @@ -736,14 +740,7 @@ static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv) > > > dev->driver = &vmlogrdr_driver; > > > dev->groups = vmlogrdr_attr_groups; > > > dev_set_drvdata(dev, priv); > > > - /* > > > - * The release function could be called after the > > > - * module has been unloaded. It's _only_ task is to > > > - * free the struct. Therefore, we specify kfree() > > > - * directly here. (Probably a little bit obfuscating > > > - * but legitime ...). > > > - */ > > > > Why is the comment not relevant after this change? Or better: why is it not > > valid before this change, which is why the code was introduced a very long > > time ago? Any reference? > > > > I've seen the warning since quite some time, but didn't change the code > > before sure that this doesn't introduce the bug described in the comment. > > From only 20 years ago: > > https://lore.kernel.org/all/20040316170812.GA14971@kroah.com/ > > The particular code (zfcp) was changed, so it doesn't have this code > (or never did?) anymore, but for the rest this may or may not still > be valid. I guess relevant may not have been the correct word. Maybe obvious? I can keep the comment but I do not really see what it adds, although reading the above thread, I suppose it was added as justification for calling kfree() as ->release() for a 'struct device'? Kind of seems like that ship has sailed since I see this all over the place as a ->release() function. I do not see how this patch could have a function change beyond that but I may be misreading or misinterpreting your full comment. Cheers, Nathan