- Adding prefaulting of fs0 to avoid page fault deadlocks.
- Fixed a bug that a vmo page_cache equivalence would simply drop a link to
an original vmo, even if the vmo could have more pages outside the page cache,
or if the vmo was not a shadow vmo.
- Fixed a bug with page allocator where recursion would corrupt global variables.
- Now going to fix or re-write a simpler page allocator that works.
Added a list of links for vm objects so they can follow
the links that point at them.
More succinct handling of the case where a vm object
is dropped. Now depending on the object's number of link
references and shadow references, upon a drop it could
either be merged, deleted or kept.
Added opener reference count for vm files. Now files
have opener count, objects have shadow and link count.
Link count is also meaningful for how many tasks have
mmap'ed that object.
R/W shadow objects must be made read-only during a fork.
When searching for a writeable shadow object, it can only be the first
object on the vma object chain, therefore not traversing the object
chain and checking only the first object is sufficient.
serving mm0, if it page faults, system deadlocks because mm0 is waiting to be served by vfs.
FIX: To fix this, mm0 will need to fork itself and keep a separate thread solely for
page fault handling.
When copying file pages back and forth, we need both dst and src
offsets since the cursor offset and read/write buffer page offsets
are different. This is now fixed.
Also done some mods to close().
- Added logic to calculate which pages are in the file and which are new
for writing.
- Nearly finished the template for sys_write.
- Need to implement write_cache_pages().
- Need to distinguish dirty/clean pages and implement flushing dirty
pages back to vfs.
sys_timer accumulates timer ticks into seconds, minutes, hours and days.
It's left to the user to calculate from days into a date. It is not yet
known if the calculation is even roughly correct.
Reduced 2 kmem_reclaim/grant calls into one kmem_control call.
Factored out mapping of the physical page as the final generic code
after all fault-specific handling is done.
Fixed the error that zero page didn't have an owner (devzero).
Fixed the error that struct dirent did not have the record length
field as u16 as expected by userspace.
Normally anon && shared pages need to COW once and any newer
accesses by other sharing processes should simply map the COW'ed
pages to themselves as writeable. We didn't have that but instead
every ANON && SHARED write fault was going into the COW path, causing
the same offset'ed page to be COW'ed twice.
Next: Factor out the l4_map code to a common point at the end of all
fault handling paths.
Separated vfs file as a specific file. vm file is not always a vfs file.
Updated the README
sys_open was not returning back to client, added that.
Added comments for future vfs additions.
Removed some commented out code.
Removed excessive printfs.
Fixed spid not initialising for mm0
Fixed some faults with fs0.
TODO:
- Need to store vfs files in a separate list.
- Need to define vnum as a vfs-file-specific data, i.e. in priv_data field of vm_file.
- Need to then fix vfs_receive_sys_open.
- fixed is_err(x), was evaluating x twice, resulting in calling a
function x twice.
- Divided task initialisation into multiple parts.
- MM0 now creates a tcb for itself and maintains memory regions of its own.
- MM0's tcb is used for mmapping other tasks' regions. MM0 mmaps and prefaults
those regions, instead of the typical mmap() and fault approach used by
non-pager tasks.
For example there's an internal shmget_shmat() path to map in other tasks'
shm utcbs. Those mappings are then prefaulted into mm0's address space using
the default fault handling path.
- FS0 now reads task data into its utcb from mm0 via a syscall.
FS0 shmat()s to utcbs of other tasks, e.g. mm0 and test0.
FS0 then crashes, that is to be fixed and where this commit is left last.
For anonymous shm, mmap now adds a shm_file and devzero behind it
as two vm_objects. Faults are handled by copy_on_write(). Just as
shadows copy r/w pages from original files, it should copy r/w
pages from devzero into the shm_file in front.
shmat/shmget uses mmap to set-up their areas.
Untested yet so bugs expected.
modified: tasks/libl4/src/init.c
modified: tasks/mm0/include/shm.h
modified: tasks/mm0/include/vm_area.h
modified: tasks/mm0/src/fault.c
modified: tasks/mm0/src/mmap.c
modified: tasks/mm0/src/shm.c
Removed setting of tag during ipc_return(). So it does not overwrite
return value anymore.
Next stage is for the tasks to map their utcb via shmget/shmat before
accessing.
