TrustZone: forcing instant switch from secure to normal world?

[David Goltzsche]

Hi Martin,

based on the commits you mentioned, I implemented a minimal kernel
module, which should receive the interrupts injected by genode.

Overall it works: My Handler gets called when I trigger a software
interrupt in genode.

However, the handler is called endlessly for a single interrupt. I
assume, i have to clear the interrupt somehow. I called
tzic_end_sw_irq(..) before returning from the handler.

Here is my code: http://pastebin.com/NDBV6qYf

Any Hints?

David

On 06/29/2015 12:05 PM, Martin Stein wrote:
> Hi David,
> 
> On 29.06.2015 09:20, Stefan Kalkowski wrote:
>>> So, my approach would be using software interrupts which sould be routed
>>> to the normal world. I played around with the svc (supervisor call)
>>> instruction, but I don't know how to route this to the secure world.
>>
>> Indeed, this seems to be the most promising approach triggering a
>> software interrupt on the secure side, and handle it in the normal
>> world. Everything that needs to be done is marking a designated SPI (ARM
>> terminology for software-triggered IRQ) as a non-secure interrupt, and
>> delegate that interrupt to your kernel module within the guest OS.
>> Moreover, you will need to extend the VM session interface with the
>> ability to trigger that designated "TrustZone interrupt", as the
>> user-level VMM is not able to access the interrupt controller directly,
>> which has to be done by the kernel itself.
> 
> On my working branches [1] I've implemented IRQ injection to provide a
> pseudo block device in a non-secure linux guest. Maybe this code gives
> you some good hints. Especially the linux commits [2] and the Genode
> commits [3] should be interesting. Please be aware that this code is
> still in progress and should not be considered as final solution.
> 
> Don't hesitate to ask if you have further questions ;)
> 
> Cheers,
> Martin
> 
> [1]
> https://github.com/m-stein/genode/tree/1497_usb_armory_demo
> https://github.com/m-stein/linux/tree/1497_usb_armory_demo
> 
> [2]
> 0fa1c63 .handle multiple replies and end interrupt
> 9ca75d0 .injected IRQ reaches the stub-block handler in linux
> 
> [3]
> 08a3b09 .prototype of inject_vm_irq kernel call
> 2927f04 .Vm_session::inject_irq(unsigned irq)
> 42865c4 .injected IRQ reaches the stub-block handler in linux
> 
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-- 
M.Sc. David Goltzsche
Institute of Operating Systems and Computer Networks
Distributed Systems Group
TU Braunschweig

www: https://www.ibr.cs.tu-bs.de/users/goltzsch
mail: goltzsche at ...290...