The endpoint receive syscalls can block and then write to userspace
memory. Since the current address space may be different after blocking,
make sure to only actually write to the user memory after returning to
the syscall handler - pass values that are on the syscall handler stack
deeper into the kernel.
In order to implement capabilities on system resources like IRQs so that
they may be restricted to drivers only, add a new 'system' kobject type,
and move the bind_irq functionality from endpoint to system.
Also fix some stack bugs passing the initial handles to a program.
- Add a tag field to all endpoint messages, which doubles as a
notification field
- Add a endpoint_bind_irq syscall to enable an endpoint to listen for
interrupt notifications. This mechanism needs to change.
- Add a temporary copy of the serial port code to nulldrv, and let it
take responsibility for COM2
Added the syscalls/helpers.h file to templatize common kobject syscall
operations. Also moved most syscall implementations to using
process::current() and thread::current() instead of asking the
scheduler.
