exception_asm.h

Go to the documentation of this file.

/*
 * Copyright (C) 2008 by Duane Ellis
 *
 * All rights reserved.
 *
 * The original code had been released as part of the LoastARM Project 
 * under GPL Version 2 and is published here under the following license
 * with kind permission from the author:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``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
 * COPYRIGHT OWNER OR CONTRIBUTORS 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.
 *
 * For additional information see http://lostarm.sourceforge.net/
 */

 /* -*- mode: asm -*- */
#if  __ASSEMBLER__

.macro  ARM7TDMI_IRQ_BUG
        /* See:  ATMEL doc DOC1156 */
        /* fix/adjust lr */
        sub     lr,lr,#4
        stmfd   sp!,{lr}
        mrs     lr,spsr

        /* BUG IS - due to pipeline the IRQ bit may be     */
        /* set right (disableing irqs) but it gets lost    */
        /* inside the pipeline, software must fix this     */
        ands    lr,lr,#ARM_CPSR_I_BIT
        ldmnefd sp!,{pc}^
        ldmfd   sp!,{lr}
        /* undo the add above cause below we will do
         * the sub again below it would be nicer to
         * 'clean this up'
         */
        add     lr,lr,#4
.endm


.macro  exception_enter, whatmode, frametype

        .if     ((\whatmode) != ARM_SVC_MODE)
        sub     lr,lr,#4
        .endif
        /* switch to system mode */
        msr     cpsr_c,#(ARM_SYS_MODE | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        /* we are now in system mode */

        /* one fallacy - we always assume
         * sysmode SP is not messed up
         */
        
        /* make room for PTRACE frame */
        sub     sp,sp,#(PTRACE_FRAME_size*4)

        /* save the world */
        stmia   sp,{r0-r14}

        /* save the return value here */
        str     r0,[sp,#(PTRACE_R0_retval_idx*4)]
        
        /* Need to go back to old mode and pickup things 
         * When we get there, we will need the sys stack
         */
        mov     r0,sp

        /* step over to the dark side */
        msr     cpsr_c,#((\whatmode) | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        /* back in offending mode */

        /* save the exception address */
        str     lr,[r0,#(4*PTRACE_R15_idx)]

        /* And the saved PSR */
        mrs     r1,spsr
        str     r1,[r0,#(4*PTRACE_CPSR_idx)]
        /* and back to supervisor mode */
        msr     cpsr_c,#(ARM_SYS_MODE | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        /* done, w/ IRQ & FIQ disabled */
        /* APP can decide to re-enable if *IT* wants to */
        .if     ((\frametype) != 0)
        mov     r1,#(\frametype)
        str     r1,[r0,#(4*PTRACE_FRAMETYPE_idx)]
        .endif
.endm

.macro  exception_exit, whatmode
        /*
         * SP = the saved state
         * we always restore via SYSMODE
         */

        /* pre-position some values */
        ldr     r0,[sp,#(PTRACE_R15_idx*4)]
        ldr     r1,[sp,#(PTRACE_CPSR_idx*4)]

        /* go to the offending mode */
        msr     cpsr_c,#((\whatmode) | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        
        mov     lr,r0
        msr     spsr,r1

        /* back to the main mode */
        msr     cpsr_c,#(ARM_SYS_MODE | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        /* restore the world */
        ldmia   sp,{r0-r14}
        .if     ((\whatmode) == ARM_SVC_MODE)
        ldr     r0,[sp,#(PTRACE_R0_retval_idx*4)]
        .endif
        add     sp,sp,#(PTRACE_FRAME_size*4)

        /* back to the offending mode */
        msr     cpsr_c,#((\whatmode) | ARM_CPSR_F_BIT | ARM_CPSR_I_BIT)
        /* and effect the return */
        movs    pc,lr

.endm

#endif