For clone, file descriptor and vm area structures need to be
separate from the tcb and reached via a pointer so that they
can be shared among multiple tcbs.
- Added automatic utcb map/prefaulting of forked tasks for fs0
so that it does not need to explicitly request those tasks from mm0.
Eliminating fs0 requests to mm0 reduce deadlock possibilities.
- Replaced kmalloc with a public malloc implementation because of a bug in kmalloc.
- Fixed a kfree bug. default_release_pages was trying to free page_array pages.
- 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.
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.
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
Tasks boot fine up to doing ipc using their utcbs.
UTCB PLAN:
- Push ipc registers into private environment instead of a shared utcb,
but map-in a shared utcb to pass on long data to server tasks.
- Shared utcb has unique virtual address for every thread.
- Forked child does inherit parent's utcb, but cannot use it to communicate to
any server. It must explicitly obtain its own utcb for that.
- Clone could have a flag to explicitly not inherit parent utcb, which is the
right thing to do.
- MM0 serves a syscall to obtain self utcb.
- By this method, upon forks tasks don't need to map-in a utcb unless they want
to pass long data.
Next issues: For every read fault, the fault must traverse the
vma's object stack until the page is found. The problem was that
we were only searching the first object, that object was a writable
shadow, and the shadow didn't have the read-only page, and the 0
return value was interpreted with IS_ERR() and failed, so address
0 was mapped into the location, and QEMU blew off.
Environment is backed by a special per-task file maintained by mm0 for each task.
This file is filled in by the env pager, by simple copying of env data into the
faulty page upon a fault. UTCB and all anon regions (stack) could use the same
scheme.
Fixed IS_ERR(x) to accept negative values that are above -1000 for errors. This
protects against false positives for pointers such as 0xE0000000.
modified: include/l4/generic/scheduler.h
modified: include/l4/macros.h
modified: src/arch/arm/exception.c
modified: tasks/fs0/include/linker.lds
modified: tasks/libl4/src/init.c
modified: tasks/libposix/shm.c
new file: tasks/mm0/include/env.h
modified: tasks/mm0/include/file.h
new file: tasks/mm0/include/lib/addr.h
deleted: tasks/mm0/include/lib/vaddr.h
modified: tasks/mm0/include/task.h
new file: tasks/mm0/include/utcb.h
new file: tasks/mm0/src/env.c
modified: tasks/mm0/src/fault.c
modified: tasks/mm0/src/file.c
modified: tasks/mm0/src/init.c
new file: tasks/mm0/src/lib/addr.c
modified: tasks/mm0/src/lib/idpool.c
deleted: tasks/mm0/src/lib/vaddr.c
modified: tasks/mm0/src/mmap.c
modified: tasks/mm0/src/shm.c
modified: tasks/mm0/src/task.c
new file: tasks/mm0/src/utcb.c
modified: tasks/test0/include/linker.lds
This will help when syscalls have long arguments individual
utcbs can be mapped to server tasks and kept mapped in until the
tasks die, as opposed to map requests every time a server task maps
a different utcb at the same virtual address.
The changes have preparation code to also passing the utcb info
through the stack as part of the environment.
To sum up env and arg regions have also been added above the stack and
env region is to be used to pass on the utcb address information at
task startup.
