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Linux running in Normal World

Posted: Tue Apr 23, 2019 3:48 pm
by pbugalski
Hi,

While looking into at91bootstrap I've found CONFIG_ENTER_NWD option, which is described as "Enable Enter the Normal World before Jumping". Do I need dedicated kernel configuration to use Linux in normal world?

Best Regards,
Piotr

Re: Linux running in Normal World

Posted: Wed Apr 24, 2019 1:28 am
by blue_z
pbugalski wrote: Do I need dedicated kernel configuration to use Linux in normal world?
No.
The opposite of Normal World (I'm guessing) is Secure Boot mode.
If you're not using Secure Boot, then the SoC always executes in Normal World (i.e. non-secured mode).

Regards

Re: Linux running in Normal World

Posted: Wed Apr 24, 2019 8:12 am
by pbugalski
Hi blue_z,

Thank you for the answer.

Opposite to normal world is secure world so proper name is non-secure world, but it doesn't fit well customer expectations. Secure boot is totally different story and you are perfectly, right that it doesn't need dedicated drivers.
Secure world is part of TrustZone (https://developer.arm.com/ip-products/s ... /trustzone) provided by ARM, this mode is used after reset. When CONFIG_ENTER_NWD is set bootloader still runs in secure world, but before entering the kernel it switch to non-secure world so Linux works in fact in that mode.
In at91bootstrap I've found monitor implementation which provides some functionality for normal world however I can't find drivers using that hence was my question.

Best Regards,
Piotr