021ARM Processor operating mode

1, user mode: USR, the normal application mode of operation;

2, Fiq mode: Fiq, fast interrupt mode, when a program is running, suddenly create an interrupt, and this interruption is a rapid interruption, then into the fast interrupt mode to run;

3, IRQ mode: IRQ, normal interrupt mode;

4, Supervisor mode: SVC, to the operating system to provide protection mode, higher authority;

5, Abort mode: abt, such as to access virtual memory, resulting in a pattern of anomalies;

6, Undefined mode: und, undefined instruction mode, when we run an instruction, if this instruction is not supported by the ARM processor, will enter this mode;

7, System mode: SYS, in ARMV4 and the above version has a mode;

Linux system for applications is running in USR mode, kernel running in SVC mode;

021ARM Processor operating mode