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/*
 * Copyright (c) 2007 Petr Stepan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/** @addtogroup arm32
 * @{
 */
/** @file
    @brief  Exception handlers and exception initialization routines.
 */

#include <arch/exception.h>
#include "aux_print/printf.h"
#include <arch/memstr.h>
#include <arch/regutils.h>
#include <interrupt.h>
#include <arch/drivers/gxemul.h>

#define PREFETCH_OFFSET     0x8
#define BRANCH_OPCODE       0xea000000
#define LDR_OPCODE      0xe59ff000
#define VALID_BRANCH_MASK   0xff000000
#define EXC_VECTORS_SIZE    0x20
#define EXC_VECTORS     0x8


#define SAVE_REGS_TO_STACK          \
    asm("stmfd sp!, {r0-r12, sp, lr}");     \
    asm("mrs r14, spsr");           \
    asm("stmfd sp!, {r14}");

#define CALL_EXC_DISPATCH(exception)        \
    asm("mov r0, %0" : : "i" (exception));  \
    asm("mov r1, sp");          \
    asm("bl exc_dispatch");     

/**Loads registers from the stack and resets SPSR before exitting exception
 * handler.
 */
#define LOAD_REGS_FROM_STACK            \
    asm("ldmfd sp!, {r14}");        \
    asm("msr spsr, r14");           \
    asm("ldmfd sp!, {r0-r12, sp, pc}^");
    
/** General exception handler.
 *  Stores registers, dispatches the exception,
 *  and finally restores registers and returns from exception processing.
 */
#define PROCESS_EXCEPTION(exception)        \
    SAVE_REGS_TO_STACK          \
    CALL_EXC_DISPATCH(exception)        \
    LOAD_REGS_FROM_STACK            

/** Updates specified exception vector to jump to given handler.
 * Addresses of handlers are stored in memory following exception vectors.
 */
static void install_handler (unsigned handler_addr, unsigned* vector)
{
    /* relative address (related to exc. vector) of the word
     * where handler's address is stored
    */
    volatile uint32_t handler_address_ptr = EXC_VECTORS_SIZE - PREFETCH_OFFSET;
    
    /* make it LDR instruction and store at exception vector */
    *vector = handler_address_ptr | LDR_OPCODE;
    
    /* store handler's address */
    *(vector + EXC_VECTORS) = handler_addr;
}

static void reset_exception_entry()
{
    PROCESS_EXCEPTION(EXC_RESET);
}

/** Low-level Software Interrupt Exception handler */
static void swi_exception_entry()
{
    PROCESS_EXCEPTION(EXC_SWI);
}

/** Low-level Undefined Instruction Exception handler */
static void undef_instr_exception_entry()
{
    PROCESS_EXCEPTION(EXC_UNDEF_INSTR);
}

/** Low-level Fast Interrupt Exception handler */
static void fiq_exception_entry()
{
    PROCESS_EXCEPTION(EXC_FIQ);
}

/** Low-level Prefetch Abort Exception handler */
static void prefetch_abort_exception_entry()
{
    asm("sub lr, lr, #4");
    PROCESS_EXCEPTION(EXC_PREFETCH_ABORT);
} 

/** Low-level Data Abort Exception handler */
static void data_abort_exception_entry()
{
    asm("sub lr, lr, #8");
    PROCESS_EXCEPTION(EXC_DATA_ABORT);
}


/** Low-level Interrupt Exception handler */
static void irq_exception_entry()
{
    asm("sub lr, lr, #4");
    PROCESS_EXCEPTION(EXC_IRQ);
}


/** Interrupt Exception handler.
 * Determines the sources of interrupt, and calls their handlers.
 */
static void irq_exception(int exc_no, istate_t* istate)
{
    uint32_t sources = gxemul_irqc_get_sources();
    int i = 0;
    for (; i < GXEMUL_IRQC_MAX_IRQ; i++) {
        if (sources & (1 << i)) {
            irq_t *irq = irq_dispatch_and_lock(i);
            if (irq) {
                /* The IRQ handler was found. */
                irq->handler(irq, irq->arg);
                spinlock_unlock(&irq->lock);
            } else {
                /* Spurious interrupt.*/
                aux_printf("cpu%d: spurious interrupt (inum=%d)\n", CPU->id, i);
            }
        }
    }
/* TODO remove after testing the above code
            noirq = 0;
            if (i == CONSOLE_IRQ) {
                char readchar = *(char*)0x10000000;
                if (readchar == 0) {
                    aux_puts("?");
                }
                else {
                    aux_printf("%c", readchar);
                }
                
            }
            else if (i == TIMER_IRQ) {
                aux_printf("\n.\n");
                //acknowledge
                *(uint32_t*)0x15000110 = 0;
            }
        }
    }

    if (noirq)
    aux_puts("IRQ exception without source\n");*/
}

/** Fills exception vectors with appropriate exception handlers.
*/
void install_exception_handlers(void)
{
    install_handler((unsigned)reset_exception_entry,
             (unsigned*)EXC_RESET_VEC);
    
    install_handler((unsigned)undef_instr_exception_entry,
             (unsigned*)EXC_UNDEF_INSTR_VEC);
    
    install_handler((unsigned)swi_exception_entry,
             (unsigned*)EXC_SWI_VEC);
    
    install_handler((unsigned)prefetch_abort_exception_entry,
             (unsigned*)EXC_PREFETCH_ABORT_VEC);
    
    install_handler((unsigned)data_abort_exception_entry,
             (unsigned*)EXC_DATA_ABORT_VEC);
    
    install_handler((unsigned)irq_exception_entry,  
             (unsigned*)EXC_IRQ_VEC);
    
    install_handler((unsigned)fiq_exception_entry,
             (unsigned*)EXC_FIQ_VEC);
}

/** Initializes exception handling.
 * 
 * Installs low-level exception handlers and then registers
 * exceptions and their handlers to kernel exception dispatcher.
 */
void exception_init(void)
{
    install_exception_handlers();
    
    exc_register(EXC_IRQ, "interrupt", (iroutine) irq_exception);
    /* TODO add next */
}

/* TODO change soon, temporary hack. */
void setup_exception_stacks()
{
    /* switch to particular mode and set "sp" there */
    uint32_t cspr = current_status_reg_read();
    current_status_reg_control_write(
            (cspr & ~STATUS_REG_MODE_MASK) | IRQ_MODE
    );
    asm("ldr sp, =irq_stack");
    current_status_reg_control_write( cspr);
    
    /* TODO if you want to test other exceptions than IRQ,
    make stack analogous to irq_stack (in start.S),
    and then set stack pointer here */
}

/** @}
 */