Thanks for reaching out!
Please let me see if I can find the location of Ostro's kernel in its BSP. If I find something useful I'll post it here.
I've an update for your case.
I've found a very useful guide for modifying Ostro's kernel, I'd suggest you to check it, you can find it in https://ostroproject.org/documentation/howtos/modifying-ostro-kernel.html.
Also, I must point out that any modifications to Joule's image and its kernel are not supported by us. Nevertheless, I encourage you to continue with your project and share your findings with the community, other user might find them useful.
Please let me know if that helps you.
It's exactly what I want, Thanks!