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

From: Auer, Lukas
Date: Thu Jan 25 2018 - 08:21:12 EST


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@xxxxxxxxxxxxxxxxx>
> Cc: "Horia GeantÄ" <horia.geanta@xxxxxxx>
> Cc: Aymen Sghaier <aymen.sghaier@xxxxxxx>
> Cc: Fabio Estevam <fabio.estevam@xxxxxxx>
> Cc: Peng Fan <peng.fan@xxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Lukas Auer <lukas.auer@xxxxxxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxx/msg276184.html