Macro obsidianos_kernel::fault

macro_rules! fault {
    ($signal: ident, $stack: ident, $kernel_panic_code: block) => { ... };
}

Defines the inner of the fault handlers

Two cases:

• There are zero process, so the fault is caused by the kernel. It is a KERNEL PANIC!
• There are at least one process, so the fault should be caused by the current process. We sends a signal to it.