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=-7.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, 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 67305C433DF for ; Fri, 26 Jun 2020 15:11:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A561206E9 for ; Fri, 26 Jun 2020 15:11:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="czwfGzo5"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="czwfGzo5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728462AbgFZPL0 (ORCPT ); Fri, 26 Jun 2020 11:11:26 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:51862 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726917AbgFZPLZ (ORCPT ); Fri, 26 Jun 2020 11:11:25 -0400 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id B04DA8EE25D; Fri, 26 Jun 2020 08:11:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1593184284; bh=9gRlHJuWfxaDuLlI6MepXpQCwc5rECThM9BQ89P4ZfU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=czwfGzo5CVll8EH44IbhLTHxG+ZQG9KZvCxLefUkJu3szWaXT1LIk14lyoLCDg4cQ UQXcJmwq7gkQpF9Tw8kvq2LSpPVaARAvXfAZVZWlfiTdQkyNkDZ1txsQt8u0PEode0 4vsf+F9R+KcOSfNLiYNyRP3oEObDvkD9vJhvaQms= Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 8tu5VS6kzL4H; Fri, 26 Jun 2020 08:11:24 -0700 (PDT) Received: from [153.66.254.194] (unknown [50.35.76.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id 8572D8EE051; Fri, 26 Jun 2020 08:11:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1593184284; bh=9gRlHJuWfxaDuLlI6MepXpQCwc5rECThM9BQ89P4ZfU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=czwfGzo5CVll8EH44IbhLTHxG+ZQG9KZvCxLefUkJu3szWaXT1LIk14lyoLCDg4cQ UQXcJmwq7gkQpF9Tw8kvq2LSpPVaARAvXfAZVZWlfiTdQkyNkDZ1txsQt8u0PEode0 4vsf+F9R+KcOSfNLiYNyRP3oEObDvkD9vJhvaQms= Message-ID: <1593184281.7381.16.camel@HansenPartnership.com> Subject: Re: [Tee-dev] [PATCHv8 1/3] optee: use uuid for sysfs driver entry From: James Bottomley To: Daniel Thompson , Sumit Garg Cc: Jerome Forissier , Maxim Uvarov , Greg Kroah-Hartman , Linux Kernel Mailing List , Jarkko Sakkinen , Arnd Bergmann , "tee-dev @ lists . linaro . org" , Jason Gunthorpe , linux-integrity@vger.kernel.org, peterhuewe@gmx.de Date: Fri, 26 Jun 2020 08:11:21 -0700 In-Reply-To: <20200626112927.vfffwdhzdjf6ndmb@holly.lan> References: <1592507935.15159.5.camel@HansenPartnership.com> <1592578844.4369.5.camel@HansenPartnership.com> <1593012069.28403.11.camel@HansenPartnership.com> <1593127902.13253.11.camel@HansenPartnership.com> <20200626112927.vfffwdhzdjf6ndmb@holly.lan> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2020-06-26 at 12:29 +0100, Daniel Thompson wrote: > On Fri, Jun 26, 2020 at 10:40:41AM +0530, Sumit Garg wrote: > > On Fri, 26 Jun 2020 at 05:01, James Bottomley > > wrote: > > > > > > On Thu, 2020-06-25 at 19:54 +0530, Sumit Garg wrote: > > > > On Wed, 24 Jun 2020 at 20:51, James Bottomley > > > > wrote: > > > > > > > > > > On Wed, 2020-06-24 at 16:17 +0530, Sumit Garg wrote: > > > > > > Apologies for delay in my reply as I was busy with some > > > > > > other stuff. > > > > > > > > > > > > On Fri, 19 Jun 2020 at 20:30, James Bottomley > > > > > > wrote: > > > > > > > > > > [...] > > > > > > > it's about consistency with what the kernel types > > > > > > > mean. When some checker detects your using little endian > > > > > > > operations on a big endian structure (like in the prink > > > > > > > for instance) they're going to keep emailing you about > > > > > > > it. > > > > > > > > > > > > As mentioned above, using different terminology is meant to > > > > > > cause more confusion than just difference in endianness > > > > > > which is manageable inside TEE. > > > > > > > > > > > > And I think it's safe to say that the kernel implements > > > > > > UUID in big endian format and thus uses %pUb whereas OP-TEE > > > > > > implements UUID in little endian format and thus uses %pUl. > > > > > > > > > > So what I think you're saying is that if we still had uuid_be > > > > > and uuid_le you'd use uuid_le, because that's exactly the > > > > > structure described in the docs. But because we renamed > > > > > > > > > > uuid_be -> uuid_t > > > > > uuid_le -> guid_t > > > > > > > > > > You can't use guid_t as a kernel type because it has the > > > > > wrong name? > > > > > > > > Isn't the rename commit description [1] pretty clear about > > > > which is the true UUID type from Linux point of view? > > > > > > I don't think the kernel code takes a position on eternal verity, > > > just on logical or arithmetic truth. We just have to deal with > > > both LE and BE UUIDs so we have appropriate types for them and > > > the LE type is now named guid_t. They're both equally correct to > > > use provided the use case matches the designed one. So does the > > > name really matter? > > > > Yes it does. I guess I have provided enough reasoning for that. > > Also, the rename commit itself illustrates its importance and > > clarifies the use case for which they are meant to be used. > > > > > If we did > > > > > > #define uuid_le_t guid_t > > > > > > would you be happy? (not that the kernel cares about karmic > > > emotional states either ...) > > > > It's not about me being happy but more about confusion and > > inconsistency it will bring. > > > > IMO, either kernel should be opinionated about UUID endianness like > > currently it is: > > > > uuid_t and its corresponding helpers (eg. UUID_INIT) follows BE > > format. > > > > or support both endianness for UUID (no common type: uuid_t) like > > we had earlier prior to rename commit: > > > > uuid_be_t and its corresponding helpers (eg. UUID_BE_INIT) follow > > BE format. uuid_le_t and its corresponding helpers (eg. > > UUID_LE_INIT) follow LE format. > > > > But even if we consider later case as well, I am still not sure if > > we can switch to uuid_le_t as it's been part of TEE core ABI > > (open_session) where UUID is passed in BE format (see LE to BE > > conversion in TEE client [1] and vice-versa in OP-TEE OS [2]) and > > won't be a backwards compatible change. > > > > [1] https://github.com/OP-TEE/optee_client/blob/master/libteec/src/ > > tee_client_api.c#L595 > > [2] https://github.com/OP-TEE/optee_os/blob/master/core/arch/arm/ke > > rnel/ree_fs_ta.c#L92 > > I'm struck that all references here are to code that does not run in > kernel space. Frankly on LKML I don't know if we should even *care* > what format UUIDs are stored in other address spaces. > > We care about is the endianness of the UUID on the interface > boundaries into and out of the kernel[1] and we care that we use the > correct kernel type to describe it. > > I understood from Jerome's post that the UUID that the kernel > manipulates are, in fact, big endian and that they should be called > uuid_t. > > Is there more going on here or is that it? As you say, a UUID to the kernel is a binary blob except for input, which to the kernel is INIT_UUID or INIT_GUID and output, which is either printk %Ub for uuid_t or %Ul for guid_t. The bit I objected to was doing a %Ul on a uuid_t because it's going to trip the static checkers. That shows me there's a confusion in the code between little and big endian UUID types, but I haven't looked further than that. James