linux-kernel - Re: [RESEND PATCH 6/6] crypto: caam: detect RNG init when TrustZone is active

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Date:   Thu, 25 Jan 2018 17:54:17 +0000
From:   Bryan O'Donoghue <pure.logic@...us-software.ie>
To:     "Auer, Lukas" <lukas.auer@...ec.fraunhofer.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "aymen.sghaier@....com" <aymen.sghaier@....com>,
        "horia.geanta@....com" <horia.geanta@....com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>
Cc:     "peng.fan@....com" <peng.fan@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ryan.harkin@...aro.org" <ryan.harkin@...aro.org>,
        "fabio.estevam@....com" <fabio.estevam@....com>,
        "rui.silva@...aro.org" <rui.silva@...aro.org>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>
Subject: Re: [RESEND PATCH 6/6] crypto: caam: detect RNG init when TrustZone
 is active

On 25/01/18 13:20, Auer, Lukas wrote:
> On Wed, 2018-01-24 at 14:50 +0000, Bryan O'Donoghue wrote:
>> When TrustZone is enabled on sec4 compatible silicon the first page
>> of the
>> CAAM is reserved for TrustZone only, this means that access to the
>> deco
>> registers is restricted and will return zero when read.
>>
>> The solution to this problem is to initialize the RNG prior to
>> TrustZone
>> being enabled or to initialize the RNG from a TrustZone context and
>> simultaneously to ensure that the job-ring registers have been
>> assigned to
>> the correct non-TrustZone context.
>>
>> Assigning of the job-ring registers is a task for u-boot or
>> OPTEE/TrustZone
>> as is the initialization of the RNG. This patch adds logic to detect
>> RNG
>> initialization if and only if TrustZone has been detected as active
>> on the
>> CAAM block.
>>
>> If TrustZone is initialized and the RNG looks to be setup - we mark
>> the RNG
>> as good to go and continue to load, else we mark the RNG as bad and
>> bail
>> out.
>>
>> More detail on the original problem and the split fix between u-boot
>> and
>> Linux is available in these two threads
>>
>> Link: https://github.com/OP-TEE/optee_os/issues/1408
>> Link: https://tinyurl.com/yam5gv9a
>> Link: https://patchwork.ozlabs.org/cover/865042
>>
>> Signed-off-by: Bryan O'Donoghue <pure.logic@...us-software.ie>
>> Cc: "Horia Geantă" <horia.geanta@....com>
>> Cc: Aymen Sghaier <aymen.sghaier@....com>
>> Cc: Fabio Estevam <fabio.estevam@....com>
>> Cc: Peng Fan <peng.fan@....com>
>> Cc: Herbert Xu <herbert@...dor.apana.org.au>
>> Cc: "David S. Miller" <davem@...emloft.net>
>> Cc: Lukas Auer <lukas.auer@...ec.fraunhofer.de>
>> ---
>>   drivers/crypto/caam/ctrl.c | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
>> index 7fd3bfc..66a7c7e 100644
>> --- a/drivers/crypto/caam/ctrl.c
>> +++ b/drivers/crypto/caam/ctrl.c
>> @@ -711,6 +711,24 @@ static int caam_probe(struct platform_device
>> *pdev)
>>   			int inst_handles =
>>   				rd_reg32(&ctrl->r4tst[0].rdsta) &
>>   								RDST
>> A_IFMASK;
>> +
>> +			/*
>> +			 * If TrustZone is active then u-boot or the
>> TrustZone
>> +			 * firmware must have initialized the RNG
>> for us else we
>> +			 * cannot do so from Linux.
>> +			 *
>> +			 * We've previously detected TrustZone so
>> now let's
>> +			 * detect if the RNG has been initialized.
>> +			 */
>> +			if (ctrlpriv->trust_zone) {
>> +				ret = -ENODEV;
>> +				if (ctrlpriv->rng4_sh_init ||
>> inst_handles)
>> +					ret = 0;
>> +				dev_info(dev, "TrustZone active RNG
>> looks %s\n",
>> +					 ret ? "uninitialized" :
>> "initialized");
>> +				break;
>> +			}
>> +
>>   			/*
>>   			 * If either SH were instantiated by
>> somebody else
>>   			 * (e.g. u-boot) then it is assumed that the
>> entropy
> 
> This (in addition to patch 5) should not be required if all RNG state
> handles are already instantiated. The instantiate_rng() function checks
> each state handle if it is already instantiated before trying to do so
> itself. DEC0 would therefore never be used and the probe call should
> succeed in non-secure mode.
> 
> I have submitted a patch [1] to u-boot that instantiates all RNG state
> handles.
> 
> Thanks,
> Lukas
> 
> [1] https://www.mail-archive.com/u-boot@lists.denx.de/msg276184.html
> 

Hi Lukas,

Yes that patch along with my patch to assign job-ring ownership looks 
like it works.

https://www.mail-archive.com/u-boot@lists.denx.de/msg275834.html

Provided both of those get in, we can drop these last two in this series 
I think.