TrustZone example on i.MX6

Adam Lackorzynski adam at os.inf.tu-dresden.de
Thu Jan 8 23:42:01 CET 2015


On Mon Jan 05, 2015 at 16:30:42 +0200, Markku Ahvenjärvi wrote:
> 
> On 05.01.2015 01:22, Adam Lackorzynski wrote:
> >On Tue Dec 23, 2014 at 15:39:09 +0200, Markku Ahvenjärvi wrote:
> >>I'm trying to run Fiasco.OC in secure world and Linux in non-secure world on
> >>i.MX6Q. For this I'm using the TrustZone example (pkg/examples/sys/vm-tz).
> >>To secure world I have given 128MB RAM starting from 0x10000000 and I
> >>modified the example to give NS world 256MB starting from 0x20000000. I've
> >>replaced atags with dtb of my board and it is copied to NS side like kernel
> >>and initrd.
> >>
> >>At first I encountered runtime exception, which I fixed by implementing
> >>following to arm_em_tz builds
> >>Thread::arch_ext_vcpu_enabled() { return true; }
> >>
> >>Now I'm having problems at early stages of NS boot, where Linux kernel is
> >>checking for the dtb magic. The code loads the dtb magic from the address
> >>I'm giving in r2 register (0x21000000), but the magic value usually have one
> >>byte or all of them incorrect.
> >>
> >>I've used JDB to dump the area of dtb after hitting that error and it shows
> >>the dtb magic properly. So for some reason the NS-world gets mangled value.
> >>Any idea what might be causing this?
> >Sounds like a caching issue.
> >
> >
> >
> >Adam
> 
> Yes, I was assuming that it is caching issue. The copyblob-function in the
> example cleans cache by calling l4_cache_clean_data, so the data should be
> in RAM.
> 
> Linux kernel expects D-cache and MMU to be disabled on boot up, how is it
> done in TrustZone? By initializing banked cp15 registers?
> 
> Can you point where these are done? I'm using 20140928 snapshot.

I'm not sure I'm getting the question right. Do you mean the non-secure
or the secure side? Anyway, yes, cp15 is used independently of the side.
It should not be switched on on the ns side initially, right?



Adam
-- 
Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/



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