- Compiles and Codezero runs as normal without touching mutex implementation
- Mutex implementation needs testing.
The mutex control syscall allows userspace programs to declare any virtual
address as a mutex lock and ask for help from the kernel syscall
for resolving locking contentions.
- Added ARM register ipc usage explanation to glue/arm/message.h
- In the current design, the unused r2 register is a system register
that kernel checks for ipc flags such as:
- IPC type: e.g. full or extended.
- In extended IPC, MR index containing message buffer ptr.
- In extended IPC, message size
- KIP's pointer to UTCB seems to work with existing l4lib ipc functions.
- Works up to clone()
- In clone we mmap() the same UTCB on each new thread - excessive.
- Generally during page fault handling, cloned threads may fault on the same page
multiple times even though a single handling would be enough for all of them.
Need to detect and handle this.
Added setting of utcb address to l4_thread_control.
This is going to be moved to exchange_registers() since we need to pass
both the utcb physical and virtual address and exregs fits such context
modification better than thread_control.
- Fixed do_mmap() so that it returns mapped address, and various bugs.
- A child seems to fork with new setup, but with incorrect return value.
Need to use and test exregs() for fork + clone.
- Shmat searches an unmapped area if input arg is invalid, do_mmap()
should do this.
- Added mutex_trylock()
- Implemented most of exchange_registers()
- thread_control() now needs a lock for operations that can modify thread context.
- thread_start() does not initialise scheduler flags, now done in thread_create.
TODO:
- Fork/clone'ed threads should retain their context in tcb, not syscall stack.
- exchange_registers() calls in userspace need cleaning up.
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.
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.
Headers 3 headers related to message registers and utcbs are now merged under
utcb.h in libl4. Some message register definitions used by the kernel are now
moved into kernel's glue/message.h. This avoids the duplication of same
definitions. Also the total number of mregs are now determined by arch-specific
kernel header, which is good.
Previously we had changed the method of setting the ipc tag from l4_ipc() call
argument to being passed as a message register.
- This change was not reflected in l4_ipc() signature as it still had a 3rd argument,
even though ignored.
- l4_set_sender and _set_tag had their arguments wrong way around.
- Previously 5 mrs were passed onto utcb instead of 6, relying on the fact that
l4_ipc tag argument was being passed in r3 directly, this wasnt true anymore
with new convention, but wasn't catered for.
TODO:
- MM0 shouldn't really allocate tids itself, but use ones supplied by C0.
- Sender tid shouldn't really passed by the sender task, but rather by C0. Otherwise
security can be easily breached by user tasks pretending to be other tasks. This
would also save us a message register.
