ARM Process state -- PSTATE
In the ARMv8-A architecture, Process state or PSTATE is an abstraction of process state information. All of the instruction sets provide instructions that operate on elements of PSTATE.
在ARMv8-A架构中，进程状态或PSTATE是进程状态信息的抽象。所有指令集都提供对PSTATE元素进行操作的指令。
The Condition flags
N Negative Condition flag. (正负条件标志)
Z Zero Condition flag. (零条件标志)
C Carry Condition flag. (进位条件标志)
V Overflow Condition flag. (溢出条件标志)
The Execution state controls
SS Software Step bit, On a reset or taking an exception to AArch64 state, this bit is set to 0.
软件单步位，在AArch64状态重置或发生异常时，此位设置为0。
IL Illegal Execution state bit, On a reset or taking an exception to AArch64 state, this bit is set to 0.
非法执行状态位，在AArch64状态重置或发生异常时，此位设置为0。
nRW Current Execution state, This bit is 0 when the current Execution state is AArch64. This bit is set to 0:
当前执行状态，当当前执行状态为AArch64时，此位为0。此位设置为0：
EL Current Exception level, On a reset to AArch64 state, this field holds the encoding for the highest implemented Exception level.
当前异常级别，重置为AArch64状态时，此字段保存最高实现异常级别的编码
SP Stack pointer register selection bit, On a reset or taking an exception to AArch64 state, this bit is set to 1, meaning that SP_ELx is selected.
堆栈指针寄存器选择位，在AArch64状态重置或发生异常时，此位设置为1，表示选择了SP_ELx。
The exception mask bits
异常掩码位
D Debug exception mask bit. On a reset or taking an exception to AArch64 state, this bit is set to 1.
调试异常掩码位。在重置或对AArch64状态进行异常时，此位设置为1。
Access control bits
PAN Privileged Access Never (PAN) state bit. This bit is implemented only when ARMv8.1-PAN is implemented
PAN特权访问从不（PAN）状态位。
UAO User Access Override (UAO) bit. This bit is implemented only when ARMv8.2-UAO is implemented.
UAO用户访问覆盖（UAO）位。此位仅在实现ARMv8.2-UAO时实现。
Timing control bits
DIT Data Independent Timing (DIT) bit. This bit is implemented only when ARMv8.4-DIT is implemented. On a reset to AArch64 state, this bit is set to 0.
DIT数据独立定时（DIT）位。此位仅在实现ARMv8.4-DIT时实现。在重置为AArch64状态时，此位设置为0