SERIAL PORT DEBUGGING
=====================

On x86_64 machines, the kernel writes all printk messages to the COM1 serial port as well as
the VGA display. The serial port baud rate is set in `arch/x86_64/init.c` with a call to
`serialcon_init()`. Right now, the default baud rate for the serial console is 115200.


VIRTUAL MACHINE
---------------

When running under QEMU, you can redirect the serial output in the following ways.

1. To standard out: `-serial stdio`
2. To a file: `-serial file:<PATH>`


REAL MACHINE
------------

If your test machine has a serial port, you can connect to it to get kernel log messages.
On your monitoring machine (a machine running something Linux-like, connected to the test machine
via serial cable), you can use `screen` to communicate two-way with the test machine over serial.

If your monitoring machine *also* has a serial port, and the two machines are connected via their
builtin serial ports, you can use the following command on the monitoring machine to establish
a connection:

`screen /dev/ttySxxx <BAUD RATE>`

If you are using a USB-to-serial adapter on the monitoring machine, you should use this command
instead:

`screen /dev/ttyUSBxxx <BAUD RATE>`

Notes:
 * `xxx` is the ID of the serial port tty.
 * <BAUD RATE> needs to be the same as that being used by the kernel (see above),
   otherwise you will get garbage data.
 * Your user account needs to be a member of the `dialout` group, otherwise you
   will need to use `sudo`.