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# SPIM S20 MIPS simulator.

# The default trap handler for spim.

# 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: $

# 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)

MiniJava-Compiler/trap.handler at main · ron-che-debugger/MiniJava-Compiler · GitHub

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