text: /****************************************************************************
   * arch/arm/src/armv8-m/arm_stackcheck.c
   *
   *   Copyright (c) 2013, 2014 PX4 Development Team. All rights reserved.
   *
   * 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 PX4 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>
  
  #ifdef CONFIG_ARMV8M_STACKCHECK
  
  /* Support per function call stack checking.
   * This code uses R10 to check for a stack overflow within function calls.
   * This has a performance impact, but will be able to catch hard to find
   * stack overflows.
   */
  
  #include <stdint.h>
  
  #include "arm_arch.h"
  #include "nvic.h"
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  void  __cyg_profile_func_enter(void *func, void *caller) naked_function;
  void  __cyg_profile_func_exit(void *func, void *caller) naked_function;
  void  __stack_overflow_trap(void) naked_function;
  
  /****************************************************************************
   * Name: __stack_overflow_trap
   ****************************************************************************/
  
  void __stack_overflow_trap(void)
  {
    /* if we get here, the stack has overflowed */
  
    uint32_t regval;
  
    /* force hard fault */
  
    regval  = getreg32(NVIC_INTCTRL);
    regval |= NVIC_INTCTRL_NMIPENDSET;
    putreg32(regval, NVIC_INTCTRL);
  
    /* XXX no need to trap it here, the fault handler gets to it */
  }
  
  /****************************************************************************
   * Name: __cyg_profile_func_enter
   ****************************************************************************/
  
  void __cyg_profile_func_enter(void *func, void *caller)
  {
      asm volatile (
              "   mrs r2, ipsr        \n" /* Check whether we are in interrupt mode */
              "   cmp r2, #0          \n" /* since we don't switch r10 on interrupt entry, we */
              "   bne 2f              \n" /* can't detect overflow of the interrupt stack. */
              "                       \n"
              "   sub r2, sp, #68     \n" /* compute stack pointer as though we just stacked a full frame */
              "   mrs r1, control     \n" /* Test CONTROL.FPCA to see whether we also need room for the FP */
              "   tst r1, #4          \n" /* context. */
              "   beq 1f              \n"
              "   sub r2, r2, #136    \n" /* subtract FP context frame size */
              "1:                     \n"
              "   cmp r2, r10         \n" /* compare stack with limit */
              "   bgt 2f              \n" /* stack is above limit and thus OK */
              "   mov r11, r2         \n" /* fault with R11 set to calculated low */
              "   b __stack_overflow_trap\n"
              "2:                     \n"
              "   bx lr               \n"
      );
  }
  
  /****************************************************************************
   * Name: __cyg_profile_func_exit
   ****************************************************************************/
  
  void __cyg_profile_func_exit(void *func, void *caller)
  {
      asm volatile("bx lr");
  }
  #endif
  