VARS

Here are all the global variables, capturing much of the state of EmbryOS

bkl                     - Big Kernel Lock

Variables that are initialized but immutable after the first BKL release
========================================================================
flat_fs                 - flat file system interface
mem_end                 - end of physical memory
plic_base               - memory address of PLIC device
ramdisk_iface           - RAM block disk interface
simple_iface            - "simple" block device interface
stack_end               - end of stack for the initial hart
ticks_per_quantum       - to measure time based on ticks
uart                    - information for the main UART device
uart_info               - information for each UART device type

Variables that are shared and protected by BKL
==============================================
free_list               - list of free frames
hart/harts              - info per hart
io_focus                - process that has the current keyboard focus
io_wait                 - circular queue of other processes waiting for input
ramdisk                 - storage for the RAM disk
ramdisk_state           - meta-data of RAM disk device (immutable currently)
run_queue               - circular queue of runnable processes
simple_state            - "simple" block device state
zombies                 - linked list of dead processes

Note that the tp register on each hart points to the current process on that
hart, which in turn points to the hart info.