NRF9160 SDK 1.4 crash in random number generation

[fastfox]

Hi,

I am trying to update from SDK 1.3 to 1.4 and struggling with crashes. COAP uses random number generator to generate new tokens to the header. First time when this happens it goes fine, but second time(when making registration update in LWM2M level) app crashes to spm_request_random_number.

I can see that there is a workaround (for preventing some secure services crash) added to this release https://devzone.nordicsemi.com/f/nordic-q-a/60850/nrf9160-secure-services-causing-a-crash but disabling or enabling that workaround makes no difference.

So far I just have to disable the whole random number generation to prevent the crash.

CONFIG_ENTROPY_CC3XX=n

I also found out that someone has made a "workaround" for LWM2M sample to something that sounds awfully similar. But I can't find any more info or known issues etc.

https://github.com/nrfconnect/sdk-nrf/commit/8b8c42f84a64c3f17cb915a4c2c76ff2450c1f31

Any ideas? I should not really leave that random number generator away as we are few weeks from going into production.

[fastfox]

I asked about the workaround in github https://github.com/nrfconnect/sdk-nrf/pull/2997

unfortunately SPM entropy issue is still being investigated internally.
There were some fixes in 1.4. but apparently, they weren't enough.
It is suspected it might be a stack overflow in SPM, 
increasing the stack prevents the crash. The SPM stack is already increased on the master.

So I'll try the stack size change and see what happens

[fastfox]

If I just could figure out how to exactly do that... Increasing the SPM stack that is. They look pretty identical with master, but I am probably looking at the wrong place. I should be looking at the stuff in https://github.com/nrfconnect/sdk-nrf/tree/master/subsys/spm right?

[Amanda Hsieh]

yes, and this https://github.com/nrfconnect/sdk-nrf/blob/master/drivers/entropy/entropy_cc310.c

-Amanda H.

[fastfox]

I am sorry, I don't understand your hint. So how do you increase the SPM stack size?

[Amanda Hsieh]

Hi, 

See this https://github.com/nrfconnect/sdk-nrf/commit/2291ddb833869ba15f2705da7e6c13851440ad68 on how to increases SPM stack size. 

-Amanda H.