source: rtems/cpukit/score/cpu/arm/arm_exc_interrupt.S @ 9b2e7143

/**
 * @file
 *
 * @ingroup ScoreCPU
 *
 * @brief ARM interrupt exception prologue and epilogue.
 */

/*
 * Copyright (c) 2009
 * embedded brains GmbH
 * Obere Lagerstr. 30
 * D-82178 Puchheim
 * Germany
 * <rtems@embedded-brains.de>
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.com/license/LICENSE.
 */

/*
 * The upper EXCHANGE_SIZE bytes of the INT stack area are used for data
 * exchange between INT and SVC mode.  Below of this is the actual INT stack.
 * The exchange area is only accessed if INT is disabled.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/asm.h>
#include <rtems/score/percpu.h>

#ifdef ARM_MULTILIB_ARCH_V4

#define EXCHANGE_LR r4
#define EXCHANGE_SPSR r5
#define EXCHANGE_CPSR r6
#define EXCHANGE_INT_SP r7

#define EXCHANGE_LIST {EXCHANGE_LR, EXCHANGE_SPSR, EXCHANGE_CPSR, EXCHANGE_INT_SP}
#define EXCHANGE_SIZE 16

#define CONTEXT_LIST {r0, r1, r2, r3, EXCHANGE_LR, EXCHANGE_SPSR, r12}
#define CONTEXT_SIZE 28

.extern _Thread_Dispatch_disable_level

.extern bsp_interrupt_dispatch

.arm
.globl arm_exc_interrupt
arm_exc_interrupt:

        /* Save exchange registers to exchange area */
        stmdb   sp, EXCHANGE_LIST

        /* Set exchange registers */
        mov     EXCHANGE_LR, lr
        mrs     EXCHANGE_SPSR, spsr
        mrs     EXCHANGE_CPSR, cpsr
        sub     EXCHANGE_INT_SP, sp, #EXCHANGE_SIZE

        /* Switch to SVC mode */
        orr     EXCHANGE_CPSR, EXCHANGE_CPSR, #0x1
        msr     cpsr, EXCHANGE_CPSR

        /*
         * Save context.  We save the LR separately because it has to be
         * restored in SVC mode.  The other registers can be restored in INT
         * mode.
         */
        stmdb   sp!, CONTEXT_LIST
        stmdb   sp!, {lr}

        /* Remember INT stack pointer */
        mov     r1, EXCHANGE_INT_SP

        /* Restore exchange registers from exchange area */
        ldmia   r1, EXCHANGE_LIST

        /* Get interrupt nest level */
        ldr     r0, =ISR_NEST_LEVEL
        ldr     r2, [r0]

        /* Switch stack if necessary and save original stack pointer */
        mov     r3, sp
        cmp     r2, #0
        moveq   sp, r1
        stmdb   sp!, {r3}

        /* Switch to THUMB instructions if necessary */
        SWITCH_FROM_ARM_TO_THUMB        r1

        /* Increment interrupt nest and thread dispatch disable level */
        ldr     r1, =_Thread_Dispatch_disable_level
        ldr     r3, [r1]
        add     r2, #1
        add     r3, #1
        str     r2, [r0]
        str     r3, [r1]

        /* Call BSP dependent interrupt dispatcher */
        bl      bsp_interrupt_dispatch

        /* Decrement interrupt nest and thread dispatch disable level */
        ldr     r0, =ISR_NEST_LEVEL
        ldr     r1, =_Thread_Dispatch_disable_level
        ldr     r2, [r0]
        ldr     r3, [r1]
        sub     r2, #1
        sub     r3, #1
        str     r2, [r0]
        str     r3, [r1]

        /* Restore stack pointer */
        SWITCH_FROM_THUMB_TO_ARM
        ldr     sp, [sp]
        SWITCH_FROM_ARM_TO_THUMB        r0

        /* Check thread dispatch disable level */
        cmp     r3, #0
        bne     thread_dispatch_done

        /* Check context switch necessary */
        ldr     r0, =DISPATCH_NEEDED
        ldrb    r1, [r0]
        cmp     r1, #0
        beq     thread_dispatch_done

        /* This aligns thread_dispatch_done on a 4 byte boundary */
#ifdef __thumb__
        nop
#endif /* __thumb__ */

do_thread_dispatch:

        /* Thread dispatch */
        bl      _Thread_Dispatch

thread_dispatch_done:

        /* Switch to ARM instructions if necessary */
        SWITCH_FROM_THUMB_TO_ARM

        /* Restore link register */
        ldmia   sp!, {lr}

        /*
         * XXX: Remember and restore stack pointer.  The data on the stack is
         * still in use.  So the stack is now in an inconsistent state.  The
         * FIQ handler implementation must not use this area.
         */
        mov     r0, sp
        add     sp, #CONTEXT_SIZE

        /* Get INT mode program status register */
        mrs     r1, cpsr
        bic     r1, r1, #0x1

        /* Switch to INT mode */
        msr     cpsr, r1

        /* Save EXCHANGE_LR and EXCHANGE_SPSR registers to exchange area */
        stmdb   sp!, {EXCHANGE_LR, EXCHANGE_SPSR}

        /* Restore context */
        ldmia   r0, CONTEXT_LIST

        /* Set return address and program status */
        mov     lr, EXCHANGE_LR
        msr     spsr, EXCHANGE_SPSR

        /* Restore EXCHANGE_LR and EXCHANGE_SPSR registers from exchange area */
        ldmia   sp!, {EXCHANGE_LR, EXCHANGE_SPSR}

        /* Return from interrupt */
        subs    pc, lr, #4

#endif /* ARM_MULTILIB_ARCH_V4 */