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/******************************************************************************

*                                                                             *

* License Agreement                                                           *

*                                                                             *

* Copyright (c) 2008 Altera Corporation, San Jose, California, USA.           *

* All rights reserved.                                                        *

*                                                                             *

* Permission is hereby granted, free of charge, to any person obtaining a     *

* copy of this software and associated documentation files (the "Software"),  *

* to deal in the Software without restriction, including without limitation   *

* the rights to use, copy, modify, merge, publish, distribute, sublicense,    *

* and/or sell copies of the Software, and to permit persons to whom the       *

* Software is furnished to do so, subject to the following conditions:        *

*                                                                             *

* The above copyright notice and this permission notice shall be included in  *

* all copies or substantial portions of the Software.                         *

*                                                                             *

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  *

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,    *

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER      *

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING     *

* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER         *

* DEALINGS IN THE SOFTWARE.                                                   *

*                                                                             *

* This agreement shall be governed in all respects by the laws of the State   *

* of California and by the laws of the United States of America.              *

*                                                                             *

* Altera does not recommend, suggest or require that this reference design    *

* file be used in conjunction or combination with any other product.          *

******************************************************************************/

#include "sys/alt_exceptions.h"

#include "nios2.h"

#include "alt_types.h"

#include "system.h"

/*

 * This file implements support for calling user-registered handlers for

 * instruction-generated exceptions. This handler could also be reached

 * in the event of a spurious interrupt.

 *

 * The handler code is optionally enabled through the "Enable

 * Instruction-related Exception API" HAL BSP setting, which will

 * define the macro below.

 */

#ifdef ALT_INCLUDE_INSTRUCTION_RELATED_EXCEPTION_API

/* Function pointer to exception callback routine */

alt_exception_result (*alt_instruction_exception_handler)

  (alt_exception_cause, alt_u32, alt_u32) = 0x0;

/* Link entry routine to .exceptions section */

int alt_instruction_exception_entry (alt_u32 exception_pc)

  __attribute__ ((section (".exceptions")));

/*

 * This is the entry point for instruction-generated exceptions handling.

 * This routine will be called by alt_exceptions_entry.S, after it determines

 * that an exception could not be handled by handlers that preceed that

 * of instruction-generated exceptions (such as interrupts).

 *

 * For this to function properly, you must register an exception handler

 * using alt_instruction_exception_register(). This routine will call

 * that handler if it has been registered. Absent a handler, it will

 * break break or hang as discussed below.

 */

int

alt_instruction_exception_entry (alt_u32 exception_pc)

{

  alt_u32 cause, badaddr;

/*

 * If the processor hardware has the optional EXCEPTIONS & BADADDR registers,

 * read them and pass their content to the user handler. These are always

 * present if the MMU or MPU is enabled, and optionally for other advanced

 * exception types via the "Extra exceptions information" setting in the

 * processor (hardware) configuration.

 *

 * If these registers are not present, the cause field will be set to

 * NIOS2_EXCEPTION_CAUSE_NOT_PRESENT. Your handling routine should

 * check the validity of the cause argument before proceeding.

 */

#ifdef NIOS2_HAS_EXTRA_EXCEPTION_INFO

  /* Get exception cause & "badaddr" */

  NIOS2_READ_EXCEPTION(cause);

  cause = ( (cause & NIOS2_EXCEPTION_REG_CAUSE_MASK) >>

              NIOS2_EXCEPTION_REG_CAUSE_OFST );

  NIOS2_READ_BADADDR(badaddr);

#else

  cause = NIOS2_EXCEPTION_CAUSE_NOT_PRESENT;

  badaddr = 0;

#endif /* NIOS2_HAS_EXTRA_EXCEPTION_INFO */

  if(alt_instruction_exception_handler) {

    /*

     * Call handler. Its return value indicates whether the exception-causing

     * instruction should be re-issued. The code that called us,

     * alt_eceptions_entry.S, will look at this value and adjust the ea

     * register as necessary

     */

    return alt_instruction_exception_handler(cause, exception_pc, badaddr);

  }

  /*

   * We got here because an instruction-generated exception occured, but no

   * handler is present. We do not presume to know how to handle it. If the

   * debugger is present, break, otherwise hang.

   *

   * If you've reached here in the debugger, consider examining the

   * EXCEPTIONS register cause bit-field, which was read into the 'cause'

   * variable above, and compare it against the exceptions-type enumeration

   * in alt_exceptions.h. This register is availabe if the MMU or MPU is

   * present, or if the "Extra exceptions information" hardware option is

   * selected.

   *

   *  If you get here then one of the following could have happened:

   *

   *  - An instruction-generated exception occured, and the processor

   *    does not have the extra exceptions feature enabled, or you

   *    have not registered a handler using

   *    alt_instruction_exception_register()

   *

   *  Some examples of instruction-generated exceptions and why they

   *  might occur:

   *

   *  - Your program could have been compiled for a full-featured

   *    Nios II core, but it is running on a smaller core, and

   *    instruction emulation has been disabled by defining

   *    ALT_NO_INSTRUCTION_EMULATION.

   *

   *    You can work around the problem by re-enabling instruction

   *    emulation, or you can figure out why your program is being

   *    compiled for a system other than the one that it is running on.

   *

   *  - Your program has executed a trap instruction, but has not

   *    implemented a handler for this instruction.

   *

   *  - Your program has executed an illegal instruction (one which is

   *    not defined in the instruction set).

   *

   *  - Your processor includes an MMU or MPU, and you have enabled it

   *    before registering an exception handler to service exceptions it

   *    generates.

   *

   * The problem could also be hardware related:

   *  - If your hardware is broken and is generating spurious interrupts

   *    (a peripheral which negates its interrupt output before its

   *    interrupt handler has been executed will cause spurious interrupts)

   */

  else {

#ifdef NIOS2_HAS_DEBUG_STUB

    NIOS2_BREAK();

#else

    while(1)

      ;

#endif /* NIOS2_HAS_DEBUG_STUB */

  }

  /* We should not get here. Remove compiler warning. */

  return NIOS2_EXCEPTION_RETURN_REISSUE_INST;

}

#endif /* ALT_INCLUDE_INSTRUCTION_RELATED_EXCEPTION_API */

/*

 * This routine indicates whether a particular exception cause will have

 * set a valid address into the BADADDR register, which is included

 * in the arguments to a user-registered instruction-generated exception

 * handler. Many exception types do not set valid contents in BADADDR;

 * this is a convenience routine to easily test the validity of that

 * argument in your handler.

 *

 * Note that this routine will return false (0) for causes

 * NIOS2_EXCEPTION_TLB_MISS and NIOS2_EXCEPTION_ECC_TLB_ERR.

 * You must read the TLBMISC.D field to determine if BADADDR

 * is valid for these (valid if TLBMISC.D = 1).

 *

 * Arguments:

 * cause:  The 5-bit exception cause field of the EXCEPTIONS register,

 *         shifted to the LSB position. You may pass the 'cause' argument

 *         in a handler you registered directy to this routine.

 *

 * Return: 1: BADADDR (bad_addr argument to handler) is valid

 *         0: BADADDR is not valid

 */

int

alt_exception_cause_generated_bad_addr(alt_exception_cause cause)

{

  switch (cause) {

  case NIOS2_EXCEPTION_SUPERVISOR_ONLY_DATA_ADDR:

  case NIOS2_EXCEPTION_MISALIGNED_DATA_ADDR:

  case NIOS2_EXCEPTION_MISALIGNED_TARGET_PC:

  case NIOS2_EXCEPTION_TLB_READ_PERM_VIOLATION:

  case NIOS2_EXCEPTION_TLB_WRITE_PERM_VIOLATION:

  case NIOS2_EXCEPTION_MPU_DATA_REGION_VIOLATION:

  case NIOS2_EXCEPTION_ECC_DATA_ERR:

    return 1;

  case NIOS2_EXCEPTION_TLB_MISS:

  case NIOS2_EXCEPTION_ECC_TLB_ERR:

    return 0;

  default:

    return 0;

  }

}