from target.h:68
enum target_debug_reason
{
DBG_REASON_DBGRQ = 0,
DBG_REASON_BREAKPOINT = 1,
DBG_REASON_WATCHPOINT = 2,
DBG_REASON_WPTANDBKPT = 3,
DBG_REASON_SINGLESTEP = 4,
DBG_REASON_NOTHALTED = 5,
DBG_REASON_EXIT = 6,
DBG_REASON_EXC_CATCH = 7,
DBG_REASON_UNDEFINED = 8,
};