Why does this ASM function not print properly?

I am trying to write a little function to print either a null-terminated or fixed-length string in a specific memory location. Here is my code:

vbrstart:
    xor eax, eax
    mov sp, 0x7a00
    mov bp, 0x6000
    mov ss, ax
    mov ds, ax
    mov es, ax
    xor ebx, ebx
    xor ecx, ecx
    push strict dword initializing
    push strict word 0x0000
    call printmsg
    jmp end


;push strict dword memloc
;push strict word length
;call printmsg
printmsg:
    pop strict dword [store_ret]
    mov [store_cx], cx
    mov [store_esi], esi
    pop cx
    pop esi
    push eax
    push ebx
    mov ah, 0x0E
    mov bx, 0x0007
    cmp cx, 0x0000
    je printnullterm
printgivenlen:
    lodsb
    cmp cx, 0x0000
    je printdone
    int 10h
    dec cx
    jmp printgivenlen
printnullterm:
    lodsb
    cmp al, 0x00
    je printdone
    int 10h
    jmp printnullterm
printdone:
    pop ebx
    pop eax
    mov esi, [store_esi]
    mov cx, [store_cx]
    push strict dword [store_ret]
    ret
printdata:
    store_cx dw 0
    store_esi dd 0
    store_ret dd 0

end:
    hlt
    jmp end

initializing db 10,13,'Initializing...',0

When tested, it prints indefinately, and doesn't stop at the null byte. Where did I make a mistake?

Solution

I see 2 problems with your code:

You've written a bootloader. Such a program runs in the 16-bit real address mode. This implies that the return address from a call will be a word and not a dword like your code is expecting.
```
printmsg:
pop word [store_ret]
```
You setup the stack in a risky manner. You need to first change the SS register and immediately after that the SP register.
```
xor ax, ax
mov ss, ax      <<< Keep these together 
mov sp, 0x7a00  <<< and in this order!
```

Since this is 16-bit code there's no need to push/pop the address as a dword.

push word initializing
...
pop si