Thanks a lot Jens.

I just want to make sure that, there was nothing fundamental problem for this.

My idea is to change op-tee kernel driver to pin the corresponding user-pages (i.e memref.buffer)  which ensures that these will not be unmapped, before making smc and unpinning them on return.

Will submit a pull request, once I have a working version.

-Aravind

---

From: Jens Wiklander <jens.wiklander@linaro.org>
Sent: Tuesday, June 14, 2016 11:45 PM
To: machiry aravind
Cc: tee-dev@lists.linaro.org; Eric Gustafson
Subject: Re: [Tee-dev] OP-TEE OS: Param Mapping in TA

 

Hi,

On Tue, Jun 14, 2016 at 11:51 PM, machiry aravind
<machiry_msidc@hotmail.com> wrote:
> Hi all,
>
>
> Is there any reason, why we expect all the memref param physical address to
> be in MEM_AREA_NSEC_SHM?

Current design is that OP-TEE tells normal world which memory to use
as shared memory, it doesn't make sense for OP-TEE to accept pointers
to memory out side that range.

>
>
> More specifically, why is it hard to map arbitrary non-secure user-space
> pages into TA?

If you want to map them, you need to make sure that they aren't
unmapped (or more specifically reused for something else) while used
in secure world.

>
>
> MEM_AREA_NSEC_SHM restriction imposes unnecessary limit on TA.
>
> If I want to implement some integrity checking mechanism on large sections
> of memory, this restriction makes it almost impossible.

Yes, but the purpose of this memory is to be used as shared memory for
communication between secure and non-secure world. You're looking for
something much more complex.

Long term I think we'd like to be able to map arbitrary non-secure
memory as parameters for TAs, both to make some use cases more
efficient but also to make MEM_AREA_NSEC_SHM optional in some
configuration. I'm not aware of any concrete plans though.

Regards,
Jens

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