[seL4] Re: Operating Systems built on top of seL4

On Sat, 31 Jul 2021, 10:17 pm William ML Leslie, < william.leslie.ttg@gmail.com> wrote:

On Sat, 31 Jul 2021, 8:54 pm Andrew Warkentin, wrote:

...

Even though the process server will run in user mode as far as the hardware and microkernel are concerned, functionally it will be akin to something above user processes but below the kernel. It will have full access to all kernel objects in the system including all user pages, CNodes, and endpoints (it won't actually map user pages except if a process opens the associated file for read/write I/O as opposed to mapping the file),

Eeep. You want untyped access to cappages?

Or maybe i read that wrong. It's reasonable to hold those sort of caps close rather than letting the application tinker with its own mapping, since in the unix domain it's a pain in the neck to maintain some invariants on fork or exec. Add CoW and demand paging to that and it's a real party.