source: mainline/kernel/arch/arm32/src/exc_handler.S@ c7fbb90

#
# Copyright (c) 2009 Vineeth Pillai
# 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.
#

.text   

.global irq_exception_entry
.global fiq_exception_entry
.global data_abort_exception_entry
.global prefetch_abort_exception_entry
.global undef_instr_exception_entry
.global swi_exception_entry
.global reset_exception_entry


# Switches to kernel stack and saves all registers there.
#
#  The stack frame created by the function looks like:
#
#              |_________________|
#              |                 |
#              |     SPSR        |
#              |                 |
#              |_________________|
#              | Stack Pointer   |
#              |      of         |
#              | Previous Mode   |
#              |_________________|
#              | Return address  |
#              |      of         |
#              | Previous Mode   |
#              |_________________|
#              |   R0  - R12     |
#              |      of         |
#              | Previous Mode   |
#              |_________________|
#              | Return address  |
#              |     from        |
#              |Exception Handler|
#              |_________________|
#              |                 |
#
#

.macro SAVE_REGS_TO_STACK
        stmfd r13!, {r0-r3}
        mov r3, sp
        add sp, sp, #16
        mrs r1, cpsr
        bic r1, r1, #0x1f
        mrs r2, spsr
        and r0, r2, #0x1f
        cmp r0, #0x10
        bne 1f

        # prev mode was usermode
        mov r0, lr

        # Switch to supervisor mode
        orr r1, r1, #0x13
        msr cpsr_c, r1

        # Load sp with [supervisor_sp]
        ldr r13, =supervisor_sp
        ldr r13, [r13]

        # Populate the stack frame
        msr spsr, r2
        mov lr, r0
        stmfd r13!, {lr}
        stmfd r13!, {r4-r12}
        ldmfd r3!, {r4-r7}
        stmfd r13!, {r4-r7}
        mov r4, r13
        stmfd r4, {r13, lr}^
        nop                     /* Cannot access r13 immediately after stm(2) */
        sub r13, r13, #8
        stmfd r13!, {r2}

        # Stop stack traces here
        mov fp, #0
        
        b 2f

        # mode was not usermode
1:
        # Switch to previous mode which is undoubtedly the supervisor mode
        orr r1, r1, r0
        mov r0, lr
        msr cpsr_c, r1

        # Populate the stack frame
        mov r1, sp
        stmfd r13!, {r0}
        stmfd r13!, {r4-r12}

        # Store r0-r3 in r4-r7 and then push it on to stack
        ldmfd r3!, {r4-r7}
        stmfd r13!, {r4-r7}

        # Push return address and stack pointer on to stack
        stmfd r13!, {lr}
        stmfd r13!, {r1}
        mov lr, r0
        msr spsr, r2
        stmfd r13!, {r2}
2:
.endm

.macro LOAD_REGS_FROM_STACK
        ldmfd r13!, {r0}
        msr spsr, r0
        and r0, r0, #0x1f
        cmp r0, #0x10
        bne 1f

        # return to user mode
        mov r0, r13
        ldmfd r0, {r13, lr}^
        nop                     /* Cannot access r13 immediately after ldm(2) */
        add r13, r13, #8
        b 2f

        # return to non-user mode
1:
        ldmfd r13!, {r1, lr}

2:
        ldmfd r13!, {r0-r12, pc}^
.endm

reset_exception_entry:
        SAVE_REGS_TO_STACK
        mov r0, #0
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

irq_exception_entry:
        sub lr, lr, #4
        SAVE_REGS_TO_STACK
        mov r0, #5
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

fiq_exception_entry:
        sub lr, lr, #4
        SAVE_REGS_TO_STACK
        mov r0, #6
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

undef_instr_exception_entry:
        SAVE_REGS_TO_STACK
        mov r0, #1
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

prefetch_abort_exception_entry:
        sub lr, lr, #4
        SAVE_REGS_TO_STACK
        mov r0, #3
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

data_abort_exception_entry:
        sub lr, lr, #8
        SAVE_REGS_TO_STACK
        mov r0, #4
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK

swi_exception_entry:
        ldr r13, =exc_stack
        SAVE_REGS_TO_STACK
        mov r0, #2
        mov r1, r13
        bl ras_check
        LOAD_REGS_FROM_STACK