source: liacs/coco/assignment4/trap.handler@ 422

# SPIM S20 MIPS simulator.

# The default trap handler for spim.

#

# Copyright (C) 1990-2000 James Larus, larus@cs.wisc.edu.

# ALL RIGHTS RESERVED.

#

# SPIM is distributed under the following conditions:

#

# You may make copies of SPIM for your own use and modify those copies.

#

# All copies of SPIM must retain my name and copyright notice.

#

# You may not sell SPIM or distributed SPIM in conjunction with a commerical

# product or service without the expressed written consent of James Larus.

#

# THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR

# IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED

# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

# PURPOSE.

#



# $Header: /cvs/coco08/group6/assignment4/trap.handler,v 1.1 2008/11/06 10:06:41 svhaastr Exp $





# Define the exception handling code.  This must go first!



        .kdata

__m1_:  .asciiz "  Exception "

__m2_:  .asciiz " occurred and ignored\n"

__e0_:  .asciiz "  [Interrupt] "

__e1_:  .asciiz ""

__e2_:  .asciiz ""

__e3_:  .asciiz ""

__e4_:  .asciiz "  [Unaligned address in inst/data fetch] "

__e5_:  .asciiz "  [Unaligned address in store] "

__e6_:  .asciiz "  [Bad address in text read] "

__e7_:  .asciiz "  [Bad address in data/stack read] "

__e8_:  .asciiz "  [Error in syscall] "

__e9_:  .asciiz "  [Breakpoint] "

__e10_: .asciiz "  [Reserved instruction] "

__e11_: .asciiz ""

__e12_: .asciiz "  [Arithmetic overflow] "

__e13_: .asciiz "  [Inexact floating point result] "

__e14_: .asciiz "  [Invalid floating point result] "

__e15_: .asciiz "  [Divide by 0] "

__e16_: .asciiz "  [Floating point overflow] "

__e17_: .asciiz "  [Floating point underflow] "

__excp: .word __e0_,__e1_,__e2_,__e3_,__e4_,__e5_,__e6_,__e7_,__e8_,__e9_

        .word __e10_,__e11_,__e12_,__e13_,__e14_,__e15_,__e16_,__e17_

s1:     .word 0

s2:     .word 0



        .ktext 0x80000080

        .set noat

        # Because we are running in the kernel, we can use $k0/$k1 without

        # saving their old values.

        move $k1 $at    # Save $at

        .set at

        sw $v0 s1       # Not re-entrent and we can't trust $sp

        sw $a0 s2

        mfc0 $k0 $13    # Cause

        sgt $v0 $k0 0x44 # ignore interrupt exceptions

        bgtz $v0 ret

        addu $0 $0 0

        li $v0 4        # syscall 4 (print_str)

        la $a0 __m1_

        syscall

        li $v0 1        # syscall 1 (print_int)

        srl $a0 $k0 2   # shift Cause reg

        syscall

        li $v0 4        # syscall 4 (print_str)

        lw $a0 __excp($k0)

        syscall

        bne $k0 0x18 ok_pc # Bad PC requires special checks

        mfc0 $a0, $14   # EPC

        and $a0, $a0, 0x3 # Is EPC word-aligned?

        beq $a0, 0, ok_pc

        li $v0 10       # Exit on really bad PC (out of text)

        syscall



ok_pc:

        li $v0 4        # syscall 4 (print_str)

        la $a0 __m2_

        syscall

        mtc0 $0, $13    # Clear Cause register

ret:    lw $v0 s1

        lw $a0 s2

        mfc0 $k0 $14    # EPC

        .set noat

        move $at $k1    # Restore $at

        .set at

        rfe             # Return from exception handler

        addiu $k0 $k0 4 # Return to next instruction

        jr $k0





# Standard startup code.  Invoke the routine main with no arguments.



        .text

        .globl __start

__start:

        lw $a0, 0($sp)  # argc

        addiu $a1, $sp, 4 # argv

        addiu $a2, $a1, 4 # envp

        sll $v0, $a0, 2

        addu $a2, $a2, $v0

        jal main

        li $v0 10

        syscall         # syscall 10 (exit)



        .globl __eoth

__eoth: