Physical memory allocation to L4linux

Adam Lackorzynski adam at
Mon Sep 15 00:35:58 CEST 2014

On Fri Sep 12, 2014 at 16:34:17 +0000, Masti  Ramya Jayaram wrote:
> I realized that the best place to modify sigma0's capabilities are
> when it is created. I see that this happens in
> kernel/fiasco/src/kern/kernel_thread-std.cpp in the init_workload()
> function. I do not exactly understand how sigma0 gathers all the
> capabilities - the code is a little hard to parse for me. Could
> someone explain this to me? Is there a way to pass only limited
> capabilities to sigma0 -aka, allow the default and then prune the
> resource tree?

So, I've changed my mind, let's not modify the kernel but sigma0. This
seems easier to me. As sigma0 is the root of memory this should not be a
problem and can be argued.
Sigma0 handles memory at first-come-first-serve approach and only gives
it out once, so allocating it before servicing client requests should
hide it from clients (see However, there's also an unmap
call which would need to be handled to not free it again. Another
approach could be to exclude the memory region when initializing the
internal data structures in  Whatever works/fits better.

Adam                 adam at

More information about the l4-hackers mailing list