From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932319AbdJJPTM (ORCPT ); Tue, 10 Oct 2017 11:19:12 -0400 Received: from mail-wm0-f50.google.com ([74.125.82.50]:43305 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932107AbdJJPTJ (ORCPT ); Tue, 10 Oct 2017 11:19:09 -0400 X-Google-Smtp-Source: AOwi7QBLL6bGjK2YdYSmHg4t9rv+2cJCcndvihXwzfoiv/rDOMiluG4rvnx/yk6UBzeZscG9HjAO6A== Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: [RFC] yamldt v0.5, now a DTS compiler too From: Pantelis Antoniou In-Reply-To: <20171010015020.GE2668@umbus.fritz.box> Date: Tue, 10 Oct 2017 18:19:03 +0300 Cc: Frank Rowand , Rob Herring , Grant Likely , Tom Rini , Franklin S Cooper Jr , Matt Porter , Simon Glass , Phil Elwell , Geert Uytterhoeven , Marek Vasut , Devicetree Compiler , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" Message-Id: <04D49C2F-9AB8-4007-AE30-7A80980220F0@konsulko.com> References: <1506973580.17981.5.camel@hp800z> <1507039989.17981.25.camel@hp800z> <1507052352.17981.48.camel@hp800z> <4D25319A-34A8-4FE6-8B14-616686D2192A@konsulko.com> <59DAAFD3.9070900@gmail.com> <20171009000053.GQ10050@umbus.fritz.box> <8306BF82-3141-4994-8EFE-D5D2052F9FE1@konsulko.com> <20171010015020.GE2668@umbus.fritz.box> To: David Gibson X-Mailer: Apple Mail (2.3273) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v9AFJHQe020756 Hi David, > On Oct 10, 2017, at 04:50 , David Gibson wrote: > > On Mon, Oct 09, 2017 at 06:07:28PM +0300, Pantelis Antoniou wrote: >> Hi David, >> >>> On Oct 9, 2017, at 03:00 , David Gibson wrote: >>> >>> On Sun, Oct 08, 2017 at 04:08:03PM -0700, Frank Rowand wrote: >>>> On 10/07/17 03:23, Pantelis Antoniou wrote: >>>>> Hi Rob, >>>>> >>>>>> On Oct 6, 2017, at 16:55 , Rob Herring wrote: >>>>>> >>>>>> On Tue, Oct 3, 2017 at 12:39 PM, Pantelis Antoniou >>>>>> wrote: >>>>>>> Hi Rob, >>>> >>>> < snip > >>>> >>>>>>> eBPF is portable, can be serialized after compiling in the schema file >>>>>>> and can be executed in the kernel. >>>>>> >>>>>> Executing in the kernel is a non-goal for me. >>>> >>>> Executing in the kernel is an anti-goal for me. >>>> >>>> We are trying to reduce the device tree footprint inside the kernel, >>>> not increase it. >>>> >>>> 99.99% of the validation should be possible statically, in the compile >>>> phase. >>>> >>>> >>>>>>> By stripping out all documentation related properties and nodes keeping >>>>>>> only the compiled filters you can generate a dtb blob that passed to >>>>>>> kernel can be used for verification of all runtime changes in the >>>>>>> kernel's live tree. eBPF is enforcing an execution model that is 'safe' >>>>>>> so we can be sure that no foul play is possible. >>>> >>>> Run time changes can be assumed correct (short of bugs in the overlay >>>> application code), if the base tree is validated, the overlay is validated, >>>> and the interface between the live tree and the overlay is a >>>> connector. >>> >>> In addition, no amount of schema validation can really protect the >>> kernel from a bad DT. Even if the schemas can 100% verify that the DT >>> is "syntactically" correct, which is ambitious, it can't protect >>> against a DT which is in the right form, but contains information that >>> is simply wrong for the hardware in question. That can stuff the >>> kernel at least as easily as an incorrectly formatted DT. >>> >> >> I disagree. >> >> There are multiple levels of validation. For now we’re only talking about >> binding validation. There can be SoC level validation, board level validation, >> revision level validation and finally application specific validation. >> >> Binding validation is making sure properties/nodes follow the binding document. >> For instance that for a foo device there’s a mandatory interrupt property. >> >> Simplified >> >> interrupt = ; >> >> Binding validation would ‘catch’ errors like assigning a string or not having the >> interrupt property available. >> >> SoC level validation would list the available interrupt number that a given >> SoC would support for that device. >> >> For example that interrupt can only take the values 10 or 99 in a given SoC. >> >> Board level validation would narrow this down even further to a value of 10 for >> a given board model. > >> Similar revision level validation would place further restriction on the allowed >> configuration. >> >> Finally application specific validation could place restriction based on the intended >> application that piece of hardware is used for. For instance devices that should not >> exceed a given power budget would have restrictions on the clock frequency of the processor >> or bus frequencies etc. > > This doesn't help. In order to do this, the validator would need > information that's essentially equivalent to the content of DT, at > which point there's no point to the DT at all - and you're left with > the problem of validating the information that the validator has. > That would be the case if hardware IP only has a single way to be configured. The industry standard nowadays is picking reusable IP blocks and integrating them together in an SoC. The driver and the binding is common for every platform that uses that block, but the allowed configuration varies according to what the hardware people uses in a given instance. > Fundamentally a validator that's useful *cannot* tell the difference > between a correct tree and one which _could_ be correct for some > theoretical hardware, but isn't for this particular hardware. > That’s why there’s reason for a nested hierarchy of bindings IMO. Completeness of validation schemes can be a differentiating factor when choosing parts for hardware design. They would sure cut down development time. > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson Regards — Pantelis From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pantelis Antoniou Subject: Re: [RFC] yamldt v0.5, now a DTS compiler too Date: Tue, 10 Oct 2017 18:19:03 +0300 Message-ID: <04D49C2F-9AB8-4007-AE30-7A80980220F0@konsulko.com> References: <1506973580.17981.5.camel@hp800z> <1507039989.17981.25.camel@hp800z> <1507052352.17981.48.camel@hp800z> <4D25319A-34A8-4FE6-8B14-616686D2192A@konsulko.com> <59DAAFD3.9070900@gmail.com> <20171009000053.GQ10050@umbus.fritz.box> <8306BF82-3141-4994-8EFE-D5D2052F9FE1@konsulko.com> <20171010015020.GE2668@umbus.fritz.box> Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20171010015020.GE2668-K0bRW+63XPQe6aEkudXLsA@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Gibson Cc: Frank Rowand , Rob Herring , Grant Likely , Tom Rini , Franklin S Cooper Jr , Matt Porter , Simon Glass , Phil Elwell , Geert Uytterhoeven , Marek Vasut , Devicetree Compiler , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org Hi David, > On Oct 10, 2017, at 04:50 , David Gibson = wrote: >=20 > On Mon, Oct 09, 2017 at 06:07:28PM +0300, Pantelis Antoniou wrote: >> Hi David, >>=20 >>> On Oct 9, 2017, at 03:00 , David Gibson = wrote: >>>=20 >>> On Sun, Oct 08, 2017 at 04:08:03PM -0700, Frank Rowand wrote: >>>> On 10/07/17 03:23, Pantelis Antoniou wrote: >>>>> Hi Rob, >>>>>=20 >>>>>> On Oct 6, 2017, at 16:55 , Rob Herring = wrote: >>>>>>=20 >>>>>> On Tue, Oct 3, 2017 at 12:39 PM, Pantelis Antoniou >>>>>> wrote: >>>>>>> Hi Rob, >>>>=20 >>>> < snip > >>>>=20 >>>>>>> eBPF is portable, can be serialized after compiling in the = schema file >>>>>>> and can be executed in the kernel. >>>>>>=20 >>>>>> Executing in the kernel is a non-goal for me. >>>>=20 >>>> Executing in the kernel is an anti-goal for me. >>>>=20 >>>> We are trying to reduce the device tree footprint inside the = kernel, >>>> not increase it. >>>>=20 >>>> 99.99% of the validation should be possible statically, in the = compile >>>> phase. >>>>=20 >>>>=20 >>>>>>> By stripping out all documentation related properties and nodes = keeping >>>>>>> only the compiled filters you can generate a dtb blob that = passed to >>>>>>> kernel can be used for verification of all runtime changes in = the >>>>>>> kernel's live tree. eBPF is enforcing an execution model that is = 'safe' >>>>>>> so we can be sure that no foul play is possible. >>>>=20 >>>> Run time changes can be assumed correct (short of bugs in the = overlay >>>> application code), if the base tree is validated, the overlay is = validated, >>>> and the interface between the live tree and the overlay is a >>>> connector. >>>=20 >>> In addition, no amount of schema validation can really protect the >>> kernel from a bad DT. Even if the schemas can 100% verify that the = DT >>> is "syntactically" correct, which is ambitious, it can't protect >>> against a DT which is in the right form, but contains information = that >>> is simply wrong for the hardware in question. That can stuff the >>> kernel at least as easily as an incorrectly formatted DT. >>>=20 >>=20 >> I disagree. >>=20 >> There are multiple levels of validation. For now we=E2=80=99re only = talking about >> binding validation. There can be SoC level validation, board level = validation, >> revision level validation and finally application specific = validation. >>=20 >> Binding validation is making sure properties/nodes follow the binding = document. >> For instance that for a foo device there=E2=80=99s a mandatory = interrupt property. >>=20 >> Simplified >>=20 >> interrupt =3D ; >>=20 >> Binding validation would =E2=80=98catch=E2=80=99 errors like = assigning a string or not having the >> interrupt property available. >>=20 >> SoC level validation would list the available interrupt number that a = given >> SoC would support for that device. >>=20 >> For example that interrupt can only take the values 10 or 99 in a = given SoC. >>=20 >> Board level validation would narrow this down even further to a value = of 10 for >> a given board model. >=20 >> Similar revision level validation would place further restriction on = the allowed >> configuration. >>=20 >> Finally application specific validation could place restriction based = on the intended >> application that piece of hardware is used for. For instance devices = that should not >> exceed a given power budget would have restrictions on the clock = frequency of the processor >> or bus frequencies etc. >=20 > This doesn't help. In order to do this, the validator would need > information that's essentially equivalent to the content of DT, at > which point there's no point to the DT at all - and you're left with > the problem of validating the information that the validator has. >=20 That would be the case if hardware IP only has a single way to be = configured. The industry standard nowadays is picking reusable IP blocks and = integrating them together in an SoC. The driver and the binding is common for every = platform that uses that block, but the allowed configuration varies according to what the = hardware people uses in a given instance. > Fundamentally a validator that's useful *cannot* tell the difference > between a correct tree and one which _could_ be correct for some > theoretical hardware, but isn't for this particular hardware. >=20 That=E2=80=99s why there=E2=80=99s reason for a nested hierarchy of = bindings IMO. Completeness of validation schemes can be a differentiating factor when choosing parts for hardware design. They would sure cut down development = time. > --=20 > David Gibson | I'll have my music baroque, and my = code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT = _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson Regards =E2=80=94 Pantelis -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html