text: /****************************************************************************
   * arch/risc-v/src/common/up_usestack.c
   *
   *   Copyright (C) 2011, 2013 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name NuttX nor the names of its contributors may be
   *    used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
   * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  
  #include <sys/types.h>
  #include <stdint.h>
  #include <sched.h>
  #include <debug.h>
  
  #include <nuttx/kmalloc.h>
  #include <nuttx/arch.h>
  
  #include "up_internal.h"
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /* MIPS requires at least a 4-byte stack alignment.  For floating point use,
   * however, the stack must be aligned to 8-byte addresses.
   */
  
  #if defined(CONFIG_LIBC_FLOATINGPOINT) || defined (CONFIG_ARCH_RV64GC)
  #  define STACK_ALIGNMENT   8
  #else
  #  define STACK_ALIGNMENT   4
  #endif
  
  /* Stack alignment macros */
  
  #define STACK_ALIGN_MASK    (STACK_ALIGNMENT-1)
  #define STACK_ALIGN_DOWN(a) ((a) & ~STACK_ALIGN_MASK)
  #define STACK_ALIGN_UP(a)   (((a) + STACK_ALIGN_MASK) & ~STACK_ALIGN_MASK)
  
  /****************************************************************************
   * Private Types
   ****************************************************************************/
  
  /****************************************************************************
   * Private Function Prototypes
   ****************************************************************************/
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: up_use_stack
   *
   * Description:
   *   Setup up stack-related information in the TCB using pre-allocated stack
   *   memory.  This function is called only from task_init() when a task or
   *   kernel thread is started (never for pthreads).
   *
   *   The following TCB fields must be initialized:
   *
   *   - adj_stack_size: Stack size after adjustment for hardware,
   *     processor, etc.  This value is retained only for debug
   *     purposes.
   *   - stack_alloc_ptr: Pointer to allocated stack
   *   - adj_stack_ptr: Adjusted stack_alloc_ptr for HW.  The
   *     initial value of the stack pointer.
   *
   * Input Parameters:
   *   - tcb: The TCB of new task
   *   - stack_size:  The allocated stack size.
   *
   *   NOTE:  Unlike up_stack_create() and up_stack_release, this function
   *   does not require the task type (ttype) parameter.  The TCB flags will
   *   always be set to provide the task type to up_use_stack() if it needs
   *   that information.
   *
   ****************************************************************************/
  
  int up_use_stack(struct tcb_s *tcb, void *stack, size_t stack_size)
  {
    size_t top_of_stack;
    size_t size_of_stack;
  
    /* Is there already a stack allocated? */
  
    if (tcb->stack_alloc_ptr)
      {
        /* Yes.. Release the old stack allocation */
  
        up_release_stack(tcb, tcb->flags & TCB_FLAG_TTYPE_MASK);
      }
  
    /* Save the new stack allocation */
  
    tcb->stack_alloc_ptr = stack;
  
    /* MIPS uses a push-down stack:  the stack grows toward loweraddresses in
     * memory.  The stack pointer register, points to the lowest, valid work
     * address (the "top" of the stack).  Items on the stack are referenced
     * as positive word offsets from sp.
     */
  
    top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size - 4;
  
    /* The MIPS stack must be aligned at word (4 byte) or double word (8 byte)
     * boundaries. If necessary top_of_stack must be rounded down to the
     * next boundary
     */
  
    top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
    size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr + 4;
  
    /* Save the adjusted stack values in the struct tcb_s */
  
    tcb->adj_stack_ptr  = (uintptr_t *)top_of_stack;
    tcb->adj_stack_size = size_of_stack;
  
    return OK;
  }
  