Re: Security Random Number Generator support

From: Marc Zyngier <maz@misterjones.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Neal Liu <neal.liu@mediatek.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sean Wang <sean.wang@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	wsd_upstream@mediatek.com, Rob Herring <robh+dt@kernel.org>,
	linux-mediatek@lists.infradead.org,
	Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
	Matt Mackall <mpm@selenic.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Crystal Guo <Crystal.Guo@mediatek.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: Security Random Number Generator support
Date: Tue, 02 Jun 2020 14:02:47 +0100	[thread overview]
Message-ID: <85dfc0142d3879d50c0ba18bcc71e199@misterjones.org> (raw)
In-Reply-To: <CAMj1kXHjAdk5=-uSh_=S9j5cz42zr3h6t+YYGy+obevuQDp0fg@mail.gmail.com>

On 2020-06-02 13:14, Ard Biesheuvel wrote:
> On Tue, 2 Jun 2020 at 10:15, Neal Liu <neal.liu@mediatek.com> wrote:
>> 
>> These patch series introduce a security random number generator
>> which provides a generic interface to get hardware rnd from Secure
>> state. The Secure state can be Arm Trusted Firmware(ATF), Trusted
>> Execution Environment(TEE), or even EL2 hypervisor.
>> 
>> Patch #1..2 adds sec-rng kernel driver for Trustzone based SoCs.
>> For security awareness SoCs on ARMv8 with TrustZone enabled,
>> peripherals like entropy sources is not accessible from normal world
>> (linux) and rather accessible from secure world (HYP/ATF/TEE) only.
>> This driver aims to provide a generic interface to Arm Trusted
>> Firmware or Hypervisor rng service.
>> 
>> 
>> changes since v1:
>> - rename mt67xx-rng to mtk-sec-rng since all MediaTek ARMv8 SoCs can 
>> reuse
>>   this driver.
>>   - refine coding style and unnecessary check.
>> 
>>   changes since v2:
>>   - remove unused comments.
>>   - remove redundant variable.
>> 
>>   changes since v3:
>>   - add dt-bindings for MediaTek rng with TrustZone enabled.
>>   - revise HWRNG SMC call fid.
>> 
>>   changes since v4:
>>   - move bindings to the arm/firmware directory.
>>   - revise driver init flow to check more property.
>> 
>>   changes since v5:
>>   - refactor to more generic security rng driver which
>>     is not platform specific.
>> 
>> *** BLURB HERE ***
>> 
>> Neal Liu (2):
>>   dt-bindings: rng: add bindings for sec-rng
>>   hwrng: add sec-rng driver
>> 
> 
> There is no reason to model a SMC call as a driver, and represent it
> via a DT node like this.

+1.

> It would be much better if this SMC interface is made truly generic,
> and wired into the arch_get_random() interface, which can be used much
> earlier.

Wasn't there a plan to standardize a SMC call to rule them all?

         M.
-- 
Who you jivin' with that Cosmik Debris?