unified/arm: add unified kernel support for ARM arch

The ARM architecture port is fitted with support for the unified kernel,
namely:

- the interrupt/exception exit code now pends PendSV if the current
  thread is not a coop thread and if the scheduler is not locked

- fiber_abort is replaced by k_thread_abort(), which takes a thread ID
  as a parameter (i.e. does not only operate on the current thread)

- the _nanokernel.flags cache of _current.flags is not used anymore
  (could be a source of bugs) and is not needed in the scheduling algo

- there is no 'task' field in the _nanokernel anymore: PendSV not calls
  _get_next_ready_thread instead

- the _nanokernel.fiber field is replaced by a more sophisticated
  ready_q, based on the microkernel's priority-bitmap-based one

- thread initialization initializes new fields in the tcs, and does not
  initialize obsolete ones

- nano_private includes nano_internal.h from the unified directory

- The FIBER, TASK and PREEMPTIBLE flags do not exist anymore: the thread
  priority drives the behaviour

- the tcs uses a dlist for queuing in both ready and wait queues instead
  of a custom singly-linked list

- other new fields in the tcs include a schedule-lock count, a
  back-pointer to init data (when the task is static) and a pointer to
  swap data, needed when a thread pending on _Swap() must be passed more
  then just one value (e.g. k_stack_pop() needs an error code and data)

- the 'fiber' and 'task' fields of _nanokernel are replaced with an O(1)
  ready queue (taken from the microkernel)

- fiberRtnValueSet() is aliased to _set_thread_return_value since it
  also operates on preempt threads now

- _set_thread_return_value_with_data() sets the swap_data field in
  addition to a return value from _Swap()

- convenience aliases are created for shorter names:

  - _current is defined as _nanokernel.current
  - _ready_q is defined as _nanokernel.ready_q

- _Swap() sets the threads's return code to -EAGAIN before swapping out
  to prevent timeouts to have to set it (solves hard issues in some
  kernel objects).

Change-Id: I36c03c362bc2908dae064ec67e6b8469fc573983
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>

arch/arm/core/swap.S

@@ -34,6 +34,10 @@ _ASM_FILE_PROLOGUE
 GTEXT(_Swap)
 GTEXT(__svc)
 GTEXT(__pendsv)
+#ifdef CONFIG_KERNEL_V2
+GTEXT(_get_next_ready_thread)
+GDATA(_k_neg_eagain)
+#endif
 
 GDATA(_nanokernel)
 
@@ -97,6 +101,12 @@ SECTION_FUNC(TEXT, __pendsv)
 
     /* find out incoming thread (fiber or task) */
 
+#ifdef CONFIG_KERNEL_V2
+    push {lr}
+    blx _get_next_ready_thread
+    pop {lr}
+    movs.n r2, r0
+#else
     /* is there a fiber ready ? */
     ldr r2, [r1, #__tNANO_fiber_OFFSET]
     cmp r2, #0
@@ -109,10 +119,13 @@ SECTION_FUNC(TEXT, __pendsv)
 	ldrne.w r0, [r2, #__tTCS_link_OFFSET]   /* then */
 	strne.w r0, [r1, #__tNANO_fiber_OFFSET] /* then */
 	ldreq.w r2, [r1, #__tNANO_task_OFFSET]  /* else */
+#endif
 
     /* r2 contains the new thread */
+#if !defined(CONFIG_KERNEL_V2)
     ldr r0, [r2, #__tTCS_flags_OFFSET]
     str r0, [r1, #__tNANO_flags_OFFSET]
+#endif
     str r2, [r1, #__tNANO_current_OFFSET]
 
     /*
@@ -189,6 +202,18 @@ SECTION_FUNC(TEXT, __svc)
 _context_switch:
 #endif
 
+#if CONFIG_KERNEL_V2
+    /*
+     * Set _Swap()'s default return code to -EAGAIN. This eliminates the
+     * need for the timeout code to invoke fiberRtnValueSet().
+     */
+
+    mrs  r2, PSP   /* thread mode, stack frame is on PSP */
+    ldr  r3, =_k_neg_eagain
+    ldr  r3, [r3, #0]
+    str  r3, [r2, #__tESF_a1_OFFSET]
+#endif
+
     /*
      * Unlock interrupts:
      * - in a SVC call, so protected against context switches