Lazily map frames

[Liblor]

Work in progress Addresses parts of #73.

Implementation of Milestone 4 before refactoring paging module to use new range tracker.

[abertschi]

Notes lazy mapping

Paging Alloc

• does lazy mapping
• [x] find free vmem region as previously. Mark region as "reserved" (introduce new type)

Paging Mapped Fixed Attr

• does eager mapping (as previously)
• alloc_vaddr_region
  • [x] check for available free or reserved vmem region, mark as "backed" by frame

Pagefault handler

1. vaddr validation

• [x] Handling if vaddr is NULL, abort with debug info (null pointer deref)
• [x] If vaddr is < start_vaddr region managed by paging:
  • [x] delegate to parent if registered, fail otherwise
• [x] more vaddr validation (if not reserved, propagate to parent handler or fail)
• [ ] guard page for stack: optional, purpose: debugging, we can implement this with the refactored paging_regions, we do not implement this yet
• [ ] guard page for heap: optional, purpose: debugging

2. Do Lazy Mapping

• [x] use frame_alloc() and map at vaddr, start mapping addr is base page aligned (round down)
  • [x] call paging mapped fixed attr to map
• [x] resume (return?)
• [x] write give up function that kills thread on fatal error

[Liblor]

return is resume

[Liblor]

• [x] #define the symbol SELF_PAGING_WORKS at the top of the file lib/aos/threads.c.

[Liblor]

Uncommenting SELF_PAGING_WORKS results in a fault in slab_alloc https://github.com/Liblor/advanced_operating_systems_2020/blob/paging/faults-handling/lib/aos/threads.c#L370

during refill https://github.com/Liblor/advanced_operating_systems_2020/blob/paging/faults-handling/lib/aos/slab.c#L99

during slab_grow https://github.com/Liblor/advanced_operating_systems_2020/blob/paging/faults-handling/lib/aos/slab.c#L63 called by https://github.com/Liblor/advanced_operating_systems_2020/blob/paging/faults-handling/lib/aos/threads.c#L221

[Liblor]

Implement paging_init_onthread(...), then we can uncomment the SELF_PAGING_WORKS :dancing_women:

[Liblor]

We merged master into this branch, see: https://github.com/Liblor/advanced_operating_systems_2020/tree/paging/faults-handling-master-merge

~New problems arose...~ It was related to the other issue, namely #89

[abertschi]

Use dynamic heap notes

• [x] morecore init: use paging_alloc to reserve heap
  • remember base and current vaddr in morecore state
• [x] morecore_alloc: increment current vaddr in morecore state
• [x] Bootstrapping: Provide initial memory to bootstrap malloc (use static buffer until init done?)
• [x] morecore_free: is never called. Asked what to do: https://moodle-app2.let.ethz.ch/mod/forum/discuss.php?d=47607, presumably not going to be implemented in base version

To tackle in #90

[eikendev]

I suggest you merge 96a59feb5a082d67effaeeeb1668102638dd3f1d in here, I made a few renamings.

[abertschi]

104 is based on this branch. changes will be merged into master in branch #104