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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 <arch/debug_print/print.h>

#include <arch/memstr.h>

#include <arch/regutils.h>

#include <interrupt.h>

#include <arch/drivers/gxemul.h>

#include <arch/mm/page_fault.h>

#include <print.h>

#include <syscall/syscall.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

extern uintptr_t supervisor_sp;

extern uintptr_t exc_stack;

inline static void setup_stack_and_save_regs()

{

asm volatile(   "ldr r13, =exc_stack        \n\

    stmfd r13!, {r0}            \n\

    mrs r0, spsr                \n\

    and r0, r0, #0x1f           \n\

    cmp r0, #0x10               \n\

    bne 1f                  \n\

                        \n\

    @prev mode was usermode         \n\

    ldmfd r13!, {r0}            \n\

    ldr r13, =supervisor_sp         \n\

    stmfd r13!, {lr}            \n\

    stmfd r13!, {r0-r12}            \n\

    stmfd r13!, {r13, lr}^          \n\

    mrs r0, spsr                \n\

    stmfd r13!, {r0}            \n\

    b 2f                    \n\

                        \n\

    @prev mode was not usermode     \n\

1:                      \n\

    stmfd r13!, {r1, r2, r3}        \n\

    mrs r1, cpsr                \n\

    mov r2, lr              \n\

    bic r1, r1, #0x1f           \n\

    orr r1, r1, r0              \n\

    mrs r0, cpsr                \n\

    msr cpsr_c, r1              \n\

                        \n\

    mov r3, r13             \n\

    stmfd r13!, {r2}            \n\

    mov r2, lr              \n\

    stmfd r13!, {r4-r12}            \n\

    mov r1, r13             \n\

    mov lr, #0              \n\

    mov sp, #0              \n\

    msr cpsr_c, r0              \n\

                        \n\

    ldmfd r13!, {r4, r5, r6, r7}        \n\

    stmfd r1!, {r4, r5, r6}         \n\

    stmfd r1!, {r7}             \n\

    stmfd r1!, {r2}             \n\

    stmfd r1!, {r3}             \n\

    mrs r0, spsr                \n\

    stmfd r1!, {r0}             \n\

    mov r13, r1             \n\

2:"

);

}

inline static void load_regs()

{

asm volatile(   "ldmfd r13!, {r0}       \n\

    msr spsr, r0                \n\

    and r0, r0, #0x1f           \n\

    cmp r0, #0x10               \n\

    bne 3f                  \n\

                        \n\

    @return to user mode            \n\

    ldmfd r13!, {r13, lr}^          \n\

    b 4f                    \n\

                        \n\

    @return to non-user mode        \n\

3:                      \n\

    ldmfd r13!, {r1, r2}            \n\

    mrs r3, cpsr                \n\

    bic r3, r3, #0x1f           \n\

    orr r3, r3, r0              \n\

    mrs r0, cpsr                \n\

    msr cpsr_c, r3              \n\

                        \n\

    mov r13, r1             \n\

    mov lr, r2              \n\

    msr cpsr_c, r0              \n\

                        \n\

    @actual return              \n\

                        \n\

    ldmfd r13, {r0-r12, pc}^        \n\

4:"

);

}

/*#define SAVE_REGS_TO_STACK            \

    asm("stmfd r13!, {r0-r12, r13, lr}");   \

    asm("mrs r14, spsr");           \

    asm("stmfd r13!, {r14}");

*/

#define CALL_EXC_DISPATCH(exception)        \

    asm("mov r0, %0" : : "i" (exception));  \

    asm("mov r1, r13");         \

    asm("bl exc_dispatch");     

/**Loads registers from the stack and resets SPSR before exitting exception

 * handler.

#define LOAD_REGS_FROM_STACK            \

    asm("ldmfd r13!, {r14}");       \

    asm("msr spsr, r14");           \

    asm("ldmfd r13!, {r0-r12, r13, pc}^");

 */

/** General exception handler.

 *  Stores registers, dispatches the exception,

 *  and finally restores registers and returns from exception processing.

 */

#define PROCESS_EXCEPTION(exception)        \

    setup_stack_and_save_regs();        \

    CALL_EXC_DISPATCH(exception)        \

    load_regs();

/* #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);

}

/** Software Interrupt handler.

 *

 * Dispatches the syscall.

 */

static void swi_exception(int exc_no, istate_t* istate)

{

    istate->r0 = syscall_handler(

        istate->r0,

        istate->r1,

        istate->r2,

        istate->r3,

        istate->r4);

}

/** Interrupt Exception handler.

 *

 * Determines the sources of interrupt, and calls their handlers.

 */

static void irq_exception(int exc_no, istate_t* istate)

{

// TODO: move somewhere to gxemul.c and use machine_irq_exception (or some similar

// name) to avoid using MACHINE == MACHINE_GXEMUL_TESTARM

#if MACHINE == MACHINE_GXEMUL_TESTARM

    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.*/

                dprintf("cpu%d: spurious interrupt (inum=%d)\n", CPU->id, i);

            }

        }

    }

#endif

/* TODO remove after testing the above code

            noirq = 0;

            if (i == CONSOLE_IRQ) {

                char readchar = *(char*)0x10000000;

                if (readchar == 0) {

                    aux_puts("?");

                }

                else {

                    dprintf("%c", readchar);

                }

            }

            else if (i == TIMER_IRQ) {

                dprintf("\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);

}

#ifdef HIGH_EXCEPTION_VECTORS

/** Activates using high exception vectors addresses. */

 static void high_vectors()

{

    uint32_t control_reg;

    asm volatile( "mrc p15, 0, %0, c1, c1": "=r" (control_reg));

    //switch on the high vectors bit

    control_reg |= CP15_R1_HIGH_VECTORS_BIT;

    asm volatile( "mcr p15, 0, %0, c1, c1" : : "r" (control_reg));

}

#endif

/** Initializes exception handling.

 *

 * Installs low-level exception handlers and then registers

 * exceptions and their handlers to kernel exception dispatcher.

 */

void exception_init(void)

{

#ifdef HIGH_EXCEPTION_VECTORS

    high_vectors();

#endif

    install_exception_handlers();

    exc_register(EXC_IRQ, "interrupt", (iroutine) irq_exception);

    exc_register(EXC_PREFETCH_ABORT, "prefetch abort", (iroutine) prefetch_abort);

    exc_register(EXC_DATA_ABORT, "data abort", (iroutine) data_abort);

    exc_register(EXC_SWI, "software interrupt", (iroutine) swi_exception);

    /* TODO add next */

}

/** Sets stack pointers in all supported exception modes.

 *

 * @param stack_ptr stack pointer

 */

void setup_exception_stacks()

{

        /* switch to particular mode and set "r13" there */

        uint32_t cspr = current_status_reg_read();

        /* IRQ stack */

        current_status_reg_control_write(

                        (cspr & ~STATUS_REG_MODE_MASK) | IRQ_MODE

        );

        asm("ldr r13, =exc_stack");

        /* abort stack */

        current_status_reg_control_write(

                        (cspr & ~STATUS_REG_MODE_MASK) | ABORT_MODE

        );

        asm("ldr r13, =exc_stack");

        /* 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 */

        current_status_reg_control_write(cspr);

}

/** @}

 */