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=-6.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,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 58209C433E0 for ; Mon, 29 Jun 2020 20:43:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CFAF20663 for ; Mon, 29 Jun 2020 20:43:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="A7bBagnv" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731624AbgF2Unv (ORCPT ); Mon, 29 Jun 2020 16:43:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731623AbgF2TOC (ORCPT ); Mon, 29 Jun 2020 15:14:02 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9DE8C08ED7E for ; Sun, 28 Jun 2020 23:55:31 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id f5so860720ljj.10 for ; Sun, 28 Jun 2020 23:55:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tJRa3lLZIGNEa0u0bubwwSGZfoJedNAcGkyPYqNgizc=; b=A7bBagnvz+CsMEc9lE6It2pGWXk9fRL3Zintjy5iI8PEvE/kGQ//XRKdnwtTJ/BX3G O4aAviDJhqgfwsn54Rxa0bWfsz1MsLfhkjcSyWywRQr/6jbaU4l+wWcEBxdbhtAx8oqT QslK/7YhyguhlNukH/0XSYiQmd7tPvOWT81/g6vsCZERYc/oNp1DnRhhA6kbR2TKnDXD BbojcHXCNvUeAHPXhtOad77ctyHVVJ+pGyhyZ7aqblW3z2I9fx/PzJqodEqwfBawklGy hxAx1Mx0Ufmye2g8oX2sp+qThavwH+xNDKrp+eTzn9Q+zDmhyBT9M1eMjXnb48twOHZK yE7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=tJRa3lLZIGNEa0u0bubwwSGZfoJedNAcGkyPYqNgizc=; b=HD51k1NwEXlYTBiKTUU1ekn80XAmzHPNiEZTh5yEGwBRYoouZnHwz+SfJ0f4jTT4Cd 6JutK3c+j/jzjjLzJF7jVixqDWBAqVTZCO2QbH58aBEQ9OOEqeGa3Sryi7BNEY/Vspm2 74FhUTtHZlCRQGm2iL45fjHldTSTe5rh9NprCraXIFsoDrLYGffX3QIs+/CjaLemibaG MPj5MNR3J/kCZHMRDan5nwySm80UxeLaHsSZTIVik403mFmPpSRTmwfXixoDj0wOxbgf t/3JgXx5FcYBPO9okEtZ5O4i2chasy2LzVXu/jl8gllxkdN5A1eAA/o9YDQ8a0ZyTKGU wvLg== X-Gm-Message-State: AOAM531flYWSgRaui6eB0osdbTuVW1MKi0HyuE3vwL9F8fSIGNu9JX0l ZnG9SP30U3g5gDMX+RNG1FgwLmn12K0l4r5SR7wkqXalAbqsvg== X-Google-Smtp-Source: ABdhPJxBGJZuEQ8BqbOfIhB8sjR3+C/M0w9SaWT9vxyNM9d4n775uSZF4RCCLgXRgJMiuLvaM8Fk0wqmaZ4lwwYr9YE= X-Received: by 2002:a2e:850b:: with SMTP id j11mr7174734lji.30.1593413730053; Sun, 28 Jun 2020 23:55:30 -0700 (PDT) MIME-Version: 1.0 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> <1593184281.7381.16.camel@HansenPartnership.com> In-Reply-To: <1593184281.7381.16.camel@HansenPartnership.com> From: Sumit Garg Date: Mon, 29 Jun 2020 12:25:18 +0530 Message-ID: Subject: Re: [Tee-dev] [PATCHv8 1/3] optee: use uuid for sysfs driver entry To: James Bottomley Cc: Daniel Thompson , 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 Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 26 Jun 2020 at 20:41, James Bottomley wrote: > > 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. This is exactly which is fixed in v9 patch-set to use %Ub on a uuid_t. > 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. >From kernel TEE subsystem perspective, it's all big endian UUID type which forms the ABI into and out of the kernel. -Sumit > > James >