....的运行时异常：地址超出范围

Question

我正在将C代码转换为MIPS，找到字符串中子字符串的位置，我无法弄清楚是什么导致地址超出范围错误“strloop：         lb $ t2，（$ t1）“（第76行）。我该如何修复错误？ 我的代码是：

    .data
    Text    : .space 28
    Key     : .space 5
    msg1    : .asciiz "Please enter the text:"
    msg2    : .asciiz "\nPlease enter the key:"
    msg3    : .asciiz "\n NOT FOUND"
    msg4    : .asciiz "The key found at:"
    .text
    main:
la $a0, msg1    
li $v0,4    
syscall

la $a0, Text    
li $a1, 28  
li $v0,8    
syscall

la $t0, Text    

la $a0, msg2    
li, $v0,4   
syscall

la $a0, Key 
li $a1,5    
li $v0,8    
syscall

la $t1, Key 

add $a0, $t1 ,$zero 
jal mstrlen
add $t2, $v0, $t2   

add $a0, $t0, $zero 
add $a1, $t1, $zero
add $a2, $t2, $zero

jal findPos 
add $t0, $t0, $v0 

add $a0, $v0, $zero 
beq $a0, $zero,K    

li $v0, 4   
la $a0, msg4        
syscall     

li $t0, 1   
move $a0, $t0
syscall


    K:  la $a1, msg3    
li $v0,4
syscall

li $v0, 10  
syscall



mstrlen:
addi $sp, $sp, -8
sw $t0,4($sp)
sw $t1,($sp)

li $t0,0 #$t0=0 
add $t1,$a0,$zero 

strloop:
    lb $t2, ($t1)
    beq $t2,28,endloop  #$t2\n 
    addi $t0,$t0,1      #$t0++
    addiu $t1,$t1,1      
    b strloop       #next i

endloop:
    add $v0, $t0, $0    
    lw $t0, 4($sp)
    lw $t1,($sp)
    addi $sp,$sp,20     #stack pointer restored
    jr $ra

＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃＃ 主功能

    # $a0 text, $a1 key, $a2 keyInt (strleng(key)
    findPos:

addi $sp, $sp, -20 
sw $t0, 16($sp)
sw $t1, 12($sp)
sw $t2, 8($sp)
sw $t3, 4($sp)
sw $t4,  ($sp)

loop:
    add $t2,$a2, $zero  
    lb $t1,($a1)        
    lb $t0,($a0)        

    beq $t0,28,endfP    

        beq $t0, $t1, L
        add $t1, $zero, $zero
        beq $t1,$t2,M
        addi $t0,$t0,1 
        b loop      

    L: addi $t1,$t1,1
    M: add $t3, $t3,$t0
       addi $t3, $t3,1
       sub $t3,$t3,$t2

    endfP: add $v0, $t3, $0
        lw $t0,16($sp)
        lw $t1,12($sp)
        lw $t2,8($sp)
        lw $t3,4($sp)
        lw $t4,($sp)
        addi $sp,$sp,20 
        jr $ra