Topic: ARM64 kernel debug

It would be desirable KGDB already on boot a stage, right after kernel start. Prompt, what Android a device to select, that with minimum efforts to adjust? With access to actual compiled source codes of a kernel. Without  boards / rare laces/dancings with an unblocking bootloader. I want to take  phone. : long doubted, can it is necessary in "mobile development", but then solved that there only userland.