Does KDB conflict with CONFIG_KERNEL_THUMB2?

Hi John & Anton,

I am Jun from ZTE landing team. The KDB does not work if I enable CONFIG_KERNEL_THUMB2 on A9 CPU. After some investigation, I find that the magic undefined instruction 0xe7ffdeff(KGDB_COMPILED_BREAK) is modified if the kernel config is enabled in arch/arm/kernel/traps.c. Then exception handler cannot be found due to modified instruction value.

Do I miss any configuration to make KDB works, or it is a bug?

Thanks! Jun