ARM: modes used in Linux

There are 7 modes in ARM.

User                 usr
Fast interrupt       fiq
Interrupt            irq
Supervisor           svc
Abort                abt
System               sys
Undefined            und

*************The following information in unreliable and still under construction***********

In Linux,

Userspace: usr mode

Kernel: svc mode

Interrupts and exceptions: irq, fiq, abt and und modes

TODO:
For what sys mode is used in Linux?


References:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0210c/Cihhcjia.html