Previously CPU statue was passed on the stack, but the compiler is
allowed to clobber values passed to it on the stack in the SysV x86 ABI.
So now leave the state on the stack but pass a pointer to it into the
ISR functions.
The syscall/sysret instructions don't swap stacks. This was bad but
passable until syscalls caused the scheduler to run, and scheduling a
task that paused due to interrupt.
Adding a new (hopefully temporary) syscall interrupt `int 0xee` to allow
me to test syscalls without stack issues before I tackle the
syscall/sysret issue.
Also implemented a basic `pause` syscall that causes the calling process
to become unready. Because nothing can wake a process yet, it never
returns.
- Scheduler now has multiple linked_lists of processes at different
priorities
- Process structure improvements
- scheduler::tick() and scheduler::schedule() separation
* It looks like UEFI enables SSE, so we need to tell clang -mno-sse for
now to not use XMM* until we're ready to save them.
* SYSCALL is working from ring3 tasks, calling console printf!
* Implement MSI style interrupts
* Move interrupt handling to device_manager for IRQs
* Give device_manager the ability to allocate IRQs
* Move achi::port to an interrupt-based scheme
