How to debug ARM assambly

Hi guys, I am learning arm assembly for teensy 3.0, I was reading about arm instruction set, but when I searched for arm compiling and debugging tools (IDE) I encountered a lot of tool. None can debug my code, it always showing a error message. The idea is, I wanna learn arm assembler but I can't. You may say, Why not C++?, I got a problem called "switch context" which is imposible to handle without assembly code. Can you tell me how to debug (virtually) assembly code?

It looks like I need a special hardware to do that.

No one knows how to learn assembly for arm?

Having just gotten a program written in assembly to work I can understand your difficultly.

You could try using gdb in simulation mode. That will help but it knows nothing about the hardware.

http://cs107e.github.io/guides/gdb/