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void exception(void)
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void exception(void)
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{
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{
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    int excno;
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    int excno;
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    __u32 epc;
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    __u32 epc;
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    __u32 epc_shift = 0;
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    __u32 epc_shift = 0;
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    pri_t pri;
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    ASSERT(CPU != NULL);
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    ASSERT(CPU != NULL);
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    /*
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    /*
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     * NOTE ON OPERATION ORDERING
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     * NOTE ON OPERATION ORDERING
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     *
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     *
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     * On entry, cpu_priority_high() must be called before exception bit is cleared.
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     * On entry, cpu_priority_high() must be called before exception bit is cleared.
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     * On exit, exception bit must be set before cpu_priority_restore() is called.
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     * On exit, exception bit must be set before cpu_priority_restore() is called.
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     */
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     */
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    pri = cpu_priority_high();
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    cpu_priority_high();
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    epc = cp0_epc_read();
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    epc = cp0_epc_read();
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    cp0_status_write(cp0_status_read() & ~ cp0_status_exl_exception_bit);
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    cp0_status_write(cp0_status_read() & ~ (cp0_status_exl_exception_bit |
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                        cp0_status_um_bit));
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    if (THREAD) {
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    if (THREAD) {
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        THREAD->saved_pri = pri;
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        THREAD->saved_epc = epc;
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        THREAD->saved_epc = epc;
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    }
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    }
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    /* decode exception number and process the exception */
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    /* decode exception number and process the exception */
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    switch (excno = (cp0_cause_read() >> 2) & 0x1f) {
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    switch (excno = (cp0_cause_read() >> 2) & 0x1f) {
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        case EXC_Int:
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        case EXC_Int:
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            break;
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            break;
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        default:
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        default:
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            panic("unhandled exception %d\n", excno);
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            panic("unhandled exception %d\n", excno);
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    }
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    }
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    if (THREAD) {
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    if (THREAD)
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        pri = THREAD->saved_pri;
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        epc = THREAD->saved_epc;
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        epc = THREAD->saved_epc;
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    }
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    /* Raise EXL bit before epc_write, so that we support
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    cp0_epc_write(epc + epc_shift);
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     * properly nested exceptions
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     */
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    cp0_status_write(cp0_status_read() | cp0_status_exl_exception_bit);
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    cp0_status_write(cp0_status_read() | cp0_status_exl_exception_bit);
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    cpu_priority_restore(pri);
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    cp0_epc_write(epc + epc_shift);
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}
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}