linux-kernel - Re: Security Random Number Generator support

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Message-ID: <85dfc0142d3879d50c0ba18bcc71e199@misterjones.org>
Date:   Tue, 02 Jun 2020 14:02:47 +0100
From:   Marc Zyngier <maz@...terjones.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Neal Liu <neal.liu@...iatek.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sean Wang <sean.wang@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>, wsd_upstream@...iatek.com,
        Rob Herring <robh+dt@...nel.org>,
        linux-mediatek@...ts.infradead.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Matt Mackall <mpm@...enic.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Crystal Guo <Crystal.Guo@...iatek.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Security Random Number Generator support

On 2020-06-02 13:14, Ard Biesheuvel wrote:
> On Tue, 2 Jun 2020 at 10:15, Neal Liu <neal.liu@...iatek.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?