From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id B33D2A0532; Mon, 3 Feb 2020 19:40:32 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 0D8911BFA4; Mon, 3 Feb 2020 19:40:32 +0100 (CET) Received: from new4-smtp.messagingengine.com (new4-smtp.messagingengine.com [66.111.4.230]) by dpdk.org (Postfix) with ESMTP id 8AD581BF81 for ; Mon, 3 Feb 2020 19:40:31 +0100 (CET) Received: from compute1.internal (compute1.nyi.internal [10.202.2.41]) by mailnew.nyi.internal (Postfix) with ESMTP id 3B6936F2B; Mon, 3 Feb 2020 13:40:30 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute1.internal (MEProxy); Mon, 03 Feb 2020 13:40:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=monjalon.net; h= from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding:content-type; s=mesmtp; bh=Sa/msjtFQwTwIaZ3UXRGBKhESvvuky/J1b/+pH4W8IM=; b=TqN+mIcq63fB AareB83vzOEXtdmJCpOznb1bbFQCVVHWTQOyDZvooCNrDhsolZV9ip410cR/Bvj6 IiL+IJSWcC3PG0jGLGzbokzunqjc0c8TlQPTPlqgmyiw7+fzbWJgLFXuxf0GwpK7 vCfY6fpQhfWuSYotyEIwzbvVlBLW3iM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; bh=Sa/msjtFQwTwIaZ3UXRGBKhESvvuky/J1b/+pH4W8 IM=; b=Tvq2Paxo1feNjJTUbN267JG8f3SFEkv3fo9N6FYGxCpvB7L3XIwV/U5hA 5rAUmIjAVDOjIvi3D2LX1nZTDp8tisntQVsCeL6jbVc59oJh3O6+M+f7xggXNXMM h5jmExSm0giRIyXYWmf1HHGJftuYD0BMZfDAVFv5coXZoa6hok4NFr7v133VKWuW rtiI4Ebqcupx/BsIIX9RmUXRT4GcT+r3XxXsmMOGB6J3/+zJZ41/rUxJa4rP9L27 w+XRVSJaxkugbpS63vNhQHP5KZRN0epHX8NYYdEBwx4TYMJIffbNm35vboxgf+Xd E/R8IPRcm0ofhgLxhUp91q24jXbgQ== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedugedrgeejgdduuddvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhephffvufffkfgjfhgggfgtsehtufertddttddvnecuhfhrohhmpefvhhhomhgr shcuofhonhhjrghlohhnuceothhhohhmrghssehmohhnjhgrlhhonhdrnhgvtheqnecukf hppeejjedrudefgedrvddtfedrudekgeenucevlhhushhtvghrufhiiigvpedtnecurfgr rhgrmhepmhgrihhlfhhrohhmpehthhhomhgrshesmhhonhhjrghlohhnrdhnvght X-ME-Proxy: Received: from xps.localnet (184.203.134.77.rev.sfr.net [77.134.203.184]) by mail.messagingengine.com (Postfix) with ESMTPA id 228B0328005A; Mon, 3 Feb 2020 13:40:27 -0500 (EST) From: Thomas Monjalon To: Ferruh Yigit Cc: "Ananyev, Konstantin" , Akhil Goyal , "Trahe, Fiona" , David Marchand , Anoob Joseph , "Kusztal, ArkadiuszX" , dev@dpdk.org, "Richardson, Bruce" , nhorman@tuxdriver.com, "Mcnamara, John" , dodji@seketeli.net, Andrew Rybchenko , aconole@redhat.com, bluca@debian.org, ktraynor@redhat.com Date: Mon, 03 Feb 2020 19:40:25 +0100 Message-ID: <2219936.atdPhlSkOF@xps> In-Reply-To: <78e8ecf2-2239-897e-e34c-aee7227f3d42@intel.com> References: <20191220152058.10739-1-david.marchand@redhat.com> <7566080.EvYhyI6sBW@xps> <78e8ecf2-2239-897e-e34c-aee7227f3d42@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Subject: Re: [dpdk-dev] [PATCH v2 4/4] add ABI checks X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 03/02/2020 18:40, Ferruh Yigit: > On 2/3/2020 5:09 PM, Thomas Monjalon wrote: > > 03/02/2020 10:30, Ferruh Yigit: > >> On 2/2/2020 2:41 PM, Ananyev, Konstantin wrote: > >>> 02/02/2020 14:05, Thomas Monjalon: > >>>> 31/01/2020 15:16, Trahe, Fiona: > >>>>> On 1/30/2020 8:18 PM, Thomas Monjalon wrote: > >>>>>> 30/01/2020 17:09, Ferruh Yigit: > >>>>>>> On 1/29/2020 8:13 PM, Akhil Goyal wrote: > >>>>>>>> > >>>>>>>> I believe these enums will be used only in case of ASYM case which is experimental. > >>>>>>> > >>>>>>> Independent from being experiment and not, this shouldn't be a problem, I think > >>>>>>> this is a false positive. > >>>>>>> > >>>>>>> The ABI break can happen when a struct has been shared between the application > >>>>>>> and the library (DPDK) and the layout of that memory know differently by > >>>>>>> application and the library. > >>>>>>> > >>>>>>> Here in all cases, there is no layout/size change. > >>>>>>> > >>>>>>> As to the value changes of the enums, since application compiled with old DPDK, > >>>>>>> it will know only up to '6', 7 and more means invalid to the application. So it > >>>>>>> won't send these values also it should ignore these values from library. Only > >>>>>>> consequence is old application won't able to use new features those new enums > >>>>>>> provide but that is expected/normal. > >>>>>> > >>>>>> If library give higher value than expected by the application, > >>>>>> if the application uses this value as array index, > >>>>>> there can be an access out of bounds. > >>>>> > >>>>> [Fiona] All asymmetric APIs are experimental so above shouldn't be a problem. > >>>>> But for the same issue with sym crypto below, I believe Ferruh's explanation makes > >>>>> sense and I don't see how there can be an API breakage. > >>>>> So if an application hasn't compiled against the new lib it will be still using the old value > >>>>> which will be within bounds. If it's picking up the higher new value from the lib it must > >>>>> have been compiled against the lib so shouldn't have problems. > >>>> > >>>> You say there is no ABI issue because the application will be re-compiled > >>>> for the updated library. Indeed, compilation fixes compatibility issues. > >>>> But this is not relevant for ABI compatibility. > >>>> ABI compatibility means we can upgrade the library without recompiling > >>>> the application and it must work. > >>>> You think it is a false positive because you assume the application > >>>> "picks" the new value. I think you miss the case where the new value > >>>> is returned by a function in the upgraded library. > >>>> > >>>>> There are also no structs on the API which contain arrays using this > >>>>> for sizing, so I don't see an opportunity for an appl to have a > >>>>> mismatch in memory addresses. > >>>> > >>>> Let me demonstrate where the API may "use" the new value > >>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 and how it impacts the application. > >>>> > >>>> Once upon a time a DPDK application counting the number of devices > >>>> supporting each AEAD algo (in order to find the best supported algo). > >>>> It is done in an array indexed by algo id: > >>>> int aead_dev_count[RTE_CRYPTO_AEAD_LIST_END]; > >>>> The application is compiled with DPDK 19.11, > >>>> where RTE_CRYPTO_AEAD_LIST_END = 3. > >>>> So the size of the application array aead_dev_count is 3. > >>>> This binary is run with DPDK 20.02, > >>>> where RTE_CRYPTO_AEAD_CHACHA20_POLY1305 = 3. > >>>> When calling rte_cryptodev_info_get() on a device QAT_GEN3, > >>>> rte_cryptodev_info.capabilities.sym.aead.algo is set to > >>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 (= 3). > >>>> The application uses this value: > >>>> ++ aead_dev_count[info.capabilities.sym.aead.algo]; > >>>> The application is crashing because of out of bound access. > >>> > >>> I'd say this is an example of bad written app. > >>> It probably should check that returned by library value doesn't > >>> exceed its internal array size. > >> > >> +1 > >> > >> Application should ignore values >= MAX. > > > > Of course, blaming the API user is a lot easier than looking at the API. > > Here the API has RTE_CRYPTO_AEAD_LIST_END which can be understood > > as the max value for the application. > > Value ranges are part of the ABI compatibility contract. > > It seems you expect the application developer to be aware that > > DPDK could return a higher value, so the application should > > check every enum values after calling an API. CRAZY. > > > > When we decide to announce an ABI compatibility and do some marketing, > > everyone is OK. But when we need to really make our ABI compatible, > > I see little or no effort. DISAPPOINTING. > > This is not to blame the user or to do less work, this is more sane approach > that library provides the _END/_MAX value and application uses it as valid range > check. > > >> Do you suggest we don't extend any enum or define between ABI breakage releases > >> to be sure bad written applications not affected? > > > > I suggest we must consider not breaking any assumption made on the API. > > Here we are breaking the enum range because nothing mentions _LIST_END > > is not really the absolute end of the enum. > > The solution is to make the change below in 20.02 + backport in 19.11.1: > > > > - _LIST_END > > + _LIST_END, /* an ABI-compatible version may increase this value */ > > + _LIST_MAX = _LIST_END + 42 /* room for ABI-compatible additions */ > > }; > > > > What is the point of "_LIST_MAX" here? _LIST_MAX is range of value that DPDK can return in the ABI contract. So the appplication can rely on the range 0.._LIST_MAX. > Application should know the "_LIST_END" of when it has been compiled for the > valid range check. Next time it is compiled "_LIST_END" may be different value > but same logic applies. No, ABI compatibility contract means you can compile your application with DPDK 19.11.0 and run it with DPDK 20.02. So _LIST_END comes from 19.11 and does not include ChachaPoly. > When "_LIST_END" is missing, application can't protect itself, in that case > library should send only the values application knows when it is compiled, this > means either we can't extend our enum/defines until next ABI breakage, or we > need to do ABI versioning to the functions that returns an enum each time enum > value extended. If we define _LIST_MAX as a bigger value than current _LIST_END, we have some room to add values in between. If (as of now) we don't have _LIST_MAX room, then yes we must version the functions returning the enum. In this case, the proper solution is to implement rte_cryptodev_info_get_v1911() so it filters out RTE_CRYPTO_AEAD_CHACHA20_POLY1305 capability. With this solution, an application compiled with DPDK 19.11 will keep seeing the same range as before, while a 20.02 application could see and use ChachaPoly. This is another proposal that I was expecting from the crypto team, instead of claiming there is no issue (and wasting precious time). > I believe it is saner to provide _END/_MAX values to the application to use. And > if required comment them to clarify the expected usage. > > But in above suggestion application can't use or rely on "_LIST_MAX", it doesn't > mean anything to application. I don't understand what you mean. I think you misunderstood what is ABI compat. > > Then *_LIST_END values could be ignored by libabigail with such a change. > > > > If such a patch is not done by tomorrow, I will have to revert > > Chacha-Poly commits before 20.02-rc2, because > > > > 1/ LIST_END, without any comment, means "size of range" > > 2/ we do not blame users for undocumented ABI changes > > 3/ we respect the ABI compatibility contract