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Subject: Re: [RESEND PATCH 0/6] Enable CAAM on i.MX7s fix TrustZone issues
Thread-Topic: [RESEND PATCH 0/6] Enable CAAM on i.MX7s fix TrustZone issues
Thread-Index: AQHTlSK1t6AdBm+Ipk2quX4Kj1dXCQ==
Date:   Thu, 25 Jan 2018 17:50:31 +0000
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On 1/24/2018 4:50 PM, Bryan O'Donoghue wrote:=0A=
> This patch-set enables CAAM on the i.MX7s and fixes a number of issues=0A=
> identified with the CAAM driver and hardware when TrustZone mode is=0A=
> enabled.=0A=
> =0A=
> The first block of patches are simple bug-fixes, followed by a second blo=
ck=0A=
> of patches which are simple enabling patches for the i.MX7Solo - note we=
=0A=
> aren't enabling for the i.MX7Dual since we don't have hardware to test th=
at=0A=
> out but it should be a 1:1 mapping for others to enable when appropriate.=
=0A=
> =0A=
> The final block in this series implements a fix for using the CAAM when=
=0A=
> OPTEE/TrustZone is enabled. The various details are logged in these=0A=
> threads.=0A=
> =0A=
> Link: https://github.com/OP-TEE/optee_os/issues/1408=0A=
> Link: https://tinyurl.com/yam5gv9a=0A=
> Link: https://patchwork.ozlabs.org/cover/865042=0A=
> =0A=
> In simple terms, when TrustZone is active the first page of the CAAM=0A=
> becomes inaccessible to Linux as it has a special 'TZ bit' associated wit=
h=0A=
> it that software cannot toggle or even view AFAIK.=0A=
If the first ("global") caam register page is not accessible, RNG init is n=
ot=0A=
the only problem. For e.g. device endianness detection won't work. A comple=
te=0A=
list could be generated by auditing all places where this page is r/w.=0A=
=0A=
IMHO the correct direction for solving such cases (i.e. Linux kernel is pro=
vided=0A=
only with access to a few job rings) is to split the driver in two independ=
ent=0A=
ones - controller driver and job ring driver - and have corresponding DT no=
des=0A=
for them. Controller DT node and one or more of the job ring DT nodes would=
 be=0A=
deleted by the boot loader / trusted firmware if needed.=0A=
Of course, the job ring DT node might need additional properties for the dr=
iver=0A=
to work.=0A=
=0A=
Thanks,=0A=
Horia=0A=
=0A=
> =0A=
> The patches here then=0A=
> =0A=
> 1. Detect when TrustZone is active=0A=
> 2. Detect if u-boot (or OPTEE) has already initialized the RNG=0A=
> =0A=
> and loads the CAAM driver in a different way - skipping over the RNG=0A=
> initialization that Linux now no-longer has permissions to carry out.=0A=
> =0A=
> Should #1 be true but #2 not be true, driver loading stops (and Rui's pat=
ch=0A=
> for the NULL pointer dereference fixes a cash on this path). If #2 is tru=
e=0A=
> but #1 is not then it's a NOP as Linux has full permission to rewrite the=
=0A=
> deco registers in the first page of CAAM registers.=0A=
> =0A=
> Finally then if #1 and #2 are true, the fixes here allow the CAAM to come=
=0A=
> up and for the RNG to be useable again.=0A=
> =0A=
> Bryan O'Donoghue (3):=0A=
>   crypto: caam: Fix endless loop when RNG is already initialized=0A=
>   crypto: caam: add logic to detect when running under TrustZone=0A=
>   crypto: caam: detect RNG init when TrustZone is active=0A=
> =0A=
> Rui Miguel Silva (3):=0A=
>   crypto: caam: Fix null dereference at error path=0A=
>   ARM: dts: imx7s: add CAAM device node=0A=
>   imx7d: add CAAM clocks=0A=
> =0A=
>  arch/arm/boot/dts/imx7s.dtsi            | 26 +++++++++++++++++++=0A=
>  drivers/clk/imx/clk-imx7d.c             |  3 +++=0A=
>  drivers/crypto/caam/ctrl.c              | 45 +++++++++++++++++++++++++++=
+++---=0A=
>  drivers/crypto/caam/intern.h            |  1 +=0A=
>  include/dt-bindings/clock/imx7d-clock.h |  5 +++-=0A=
>  5 files changed, 76 insertions(+), 4 deletions(-)=0A=
> =0A=