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

*                                                                             *

* License Agreement                                                           *

*                                                                             *

* Copyright (c) 2013 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   *

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* 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.                         *

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* 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.              *

*                                                                             *

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

/*

 * This is the code called at the beginning of the exception handler

 * to detect a likely fatal ECC error exception and then jump to

 * user-provided code to handle it.

 *

 * This code is pulled in from a .globl in alt_ecc_fatal_exception.c.

 * This scheme is used so that if a handler is never registered, then this

 * code will not appear in the generated executable, thereby improving

 * code footprint.

 *

 * This code is located in its own section that the linker script

 * explicitly mentions and ensures it gets linked at the beginning

 * of the exception handler.

 */

        /*

         * Pull in the exception handler register save code.

         */

        .globl alt_exception

        .section .exceptions.entry.ecc_fatal, "xa"

        /*

         * This might be handling an unrecoverable ECC error exception

         * in the register file and/or data cache.

         * Must avoid reading registers or performing load/store instructions

         * before this is determined because they could trigger another

         * unrecoverable ECC error exception and create an infinite loop.

         *

         * The EXCEPTION register is always present when ECC is present.

         * Bit 31 of this register indicates that there was an unrecoverable

         * ECC error exception in the register file and/or data cache.

         * Test this (using blt to check sign bit) to determine if this is

         * what we are dealing with.  Otherwise, just do normal processing.

         *

         * Jump to an application-provided routine to handle this condition.

         * Pass in the return address in the et register in case this code

         * can clean up the ECC error and then return here (unlikely).

         *

         * Runtime stack checking can't be enabled when ECC is present

         * because they both want to use the et register.

         */

        rdctl et, exception

        bge et, r0, alt_exception_not_ecc_fatal /* Not ECCFTL if bit 31 is 0 */

        /*

         * Load ECC fatal handler pointer into et register.

         * Using a ldwio is safe because it completely bypasses the data cache.

         */

        movhi et, %hi(alt_exception_ecc_fatal_handler)

        ori   et, et, %lo(alt_exception_ecc_fatal_handler)

        ldwio et, 0(et)

        /*

         * If ECC fatal handler pointer is not 0, assume a handler

         * has been provided by the application.

         */

        beq et, r0, alt_exception_not_ecc_fatal

        /*

         * The et register contains the address of the ECC fatal handler.

         * Jump to this address to invoke the handler.

         */

        jmp et

        /*

         * An ECC fatal handler can jump to this label if it able

         * to recover from the fatal error (rare) and wants to continue

         * with normal exception processing.

         */

.globl alt_exception_not_ecc_fatal

alt_exception_not_ecc_fatal: