Package list ioport / fresh-snapshots/main

Tree @fresh-snapshots/main (Download .tar.gz)

I/O port access from the command line
By Richard W.M. Jones

This package adds commands to access machine I/O ports directly.  For

  outw 0x443 0xf
  inb 0x278

Note most of the time you should never use these commands unless you
know what you are doing.


The commands are pretty much used as you would expect.  For additional
help, use '--help' and/or read the manual page.

You will need to run the commands as root.  Strictly speaking you will
need CAP_SYS_RAWIO capability.


At first glance it would seem that /dev/port would be the best way to
access I/O ports.  However /dev/port under Linux is fundamentally
flawed because it only allows byte-sized access to ports.  For example
if you write a single long (4 bytes) it will turn that into 4
individual outb operations.

Instead we use iopl(2) to raise our I/O privilege level so that we can
do the correct in<size> and out<size> operation as requested.