ARM ThumbEE自动空指针检查

Question

在ARM中，Thumb-EE指令集支持自动空指针检查。

In ThumbEE state, the processor uses almost the same instruction set as Thumb-2 although     some instructions behave differently, and a few are removed, or added.
The key differences are:
additional state changing instructions in both Thumb state and ThumbEE state
new instructions to branch to handlers
null pointer checking on loads and stores
an additional instruction in ThumbEE state to check array bounds
some other modifications to the load, store, and branch instructions

ARM手册说，当thumb-EE指令尝试引用空指针时，将调用＆＃39;处理程序。但是谁设置了这个处理程序的地址？怎么样？什么时候？我无法从ARM Thumb-EE手册中得到答案。

Answer 1

请参阅“ARM体系结构参考手册”（ARM DDI 0406C）中的“B1.12 Thumb Execution Environment”部分。

ThumbEE检查处理程序的基址保存在TEEHBR寄存器中，该寄存器位于CP14 sysrem寄存器空间中：

MRC p14, 6, <Rt>, c1, c0, 0 ; Read TEEHBR into Rt
MCR p14, 6, <Rt>, c1, c0, 0 ; Write Rt to TEEHBR

请注意，与Jazelle一样，ThumbEE已被ARM弃用。