Push Each Character of a String Into a Stack MIPS - string

Question

So I'm working on a project in MIPS to check if a string input by the user is a palindrome or not. The part I'm stuck on is reading the string and pushing each character of the string into the stack one by one (the PushLoop part of the code). When I debug it, the program seems to think I haven't entered anything at all. Here's what I have so far:
.text
main:
li $v0, 4 # Prints str1
la $a0, str1
syscall
jal Init # Sets $s0 equal to $sp to compare if the stack is empty later
li $v0, 8 # Read String
la $a0, buffer # Loads memory buffer (100)
li $a1, 100 # Defines length of buffer
syscall
la $t0, buffer # Moves base register to $t0
PushLoop:
lb $a2, ($t0) # Loads current character into $a2
beqz $a2, fin # if $a2 is equal to zero, the loop is terminated
jal Push # Pushes what is stored in $a0 to the stack
add $t0, $t0, -8 # Subtracts from buffer
j PushLoop
fin:
la $t0, buffer # Resets the memory buffer (I think)
PopLoop:
jal IsEmpty # Checks if the stack is empty
lb $a2, ($t0) # Loads current character into $a2
beq $v0, 1, isPal # If stack is empty, jump to isPal
jal Pop # Pops what is stored in the stack to $t1
add $t0, $t0, -8 # Subtracts from buffer
bne $a2, $t1, notPal
j PopLoop
notPal:
li $v0, 4 # Prints str3
la $a0, str3
syscall
li $v0, 0 # loads 0 into $v0
j end
isPal:
li $v0, 4 # Prints str2
la $a0, str2
syscall
li $v0, 1 # loads 1 into $v0
j end
#EXIT
end:
li $v0, 10 # ends the program
syscall
Push:
addi $sp, $sp, -8 # Move stack pointer
sb $a2, ($sp) # Store contents of $a2 at ($sp)
jr $ra
Pop:
lw $t1, ($sp) # Pop char from stack and store in $t1
addi $sp, $sp, 8 # Move stack pointer
jr $ra
Init:
add $s0, $sp, $zero # Sets $s0 equal to $sp
jr $ra
IsEmpty:
beq $sp, $s0, Yes # If $s0 is equal to the initial value of $sp, then stack is empty
li $v0, 0 # Loads 0 into $v0
jr $ra
Yes:
li $v0, 1 # Loads 1 into $v0
jr $ra
.data # Data declaration section
str1: .asciiz "Please enter a String: "
str2: .asciiz "Is a palindrome!"
str3: .asciiz "Is NOT a palindrome"
buffer: .space 100
I'm sure there are more things wrong with the code, but I'm just trying to squash one bug at a time. Thanks so much for helping me out!

Answer 1

You're not using syscall 8 properly:
li $v0, 8 # Read String
la $t0, buffer # Loads memory buffer (100)
syscall
If you read the description of syscall 8, it says "Arguments $a0 = buffer, $a1 = length". So those three lines of code should be changed into something like:
li $v0, 8 # Read String
la $a0, buffer
li $a1, 100
syscall
Then you can do la $t0, buffer after the syscall if you still want to use $t0 as the base register for the memory reads in PushLoop.