Why NASM : Segmentation Fault 11 in macOS? - macos

Question

I am studying NASM on MacOS.
I'm trying to implement a single line spacing using a function, but I have a problem.
SYS_EXIT equ 0x1
SYS_READ equ 0x3
SYS_WRITE equ 0x4
STDIN equ 0x1
STDOUT equ 0x2
segment .data
Msg_Line db " ", 0xA, 0x0
Len_Line equ $ - Msg_Line
Msg_FirstPrompt db "Enter a Digit : "
Len_FirstPrompt equ $ - Msg_FirstPrompt
Msg_SecondPrompt db "Please Enter a Second Digit : "
Len_SecondPrompt equ $ - Msg_SecondPrompt
Msg_ThirdPrompt db "The Sum is : "
Len_ThirdPrompt equ $ - Msg_ThirdPrompt
segment .bss
Bss_FirstNumber resb 2
Bss_SecondNumber resb 2
Bss_Result resb 1
section .text
global EntryPoint
Endl:
push dword eax
push dword Len_Line
push dword Msg_Line
push dword STDOUT
sub esp, 0x4
mov eax, SYS_WRITE
int 0x80
pop eax
ret 0x4
EntryPoint:
; Print First Prompt
push dword Len_FirstPrompt
push dword Msg_FirstPrompt
push dword STDOUT
sub esp, 0x4
mov eax, SYS_WRITE
int 0x80
; Get Digit
push dword 2
push dword Bss_FirstNumber
push dword STDIN
sub esp, 0x4
mov eax, SYS_READ
int 0x80
; Print Second Prompt
push dword Len_SecondPrompt
push dword Msg_SecondPrompt
push dword STDOUT
sub esp, 0x4
mov eax, SYS_WRITE
int 0x80
; Get Second Digit
push dword 2
push dword Bss_SecondNumber
push dword STDIN
sub esp, 0x4
mov eax, SYS_READ
int 0x80
; +operator use
mov eax, [Bss_FirstNumber]
sub eax, '0'
mov ebx, [Bss_SecondNumber]
sub ebx, '0'
add eax, ebx
add eax, '0'
mov [Bss_Result], eax
; Print Result Prompt
push dword Len_ThirdPrompt
push dword Msg_ThirdPrompt
push dword STDOUT
sub esp, 0x4
mov eax, SYS_WRITE
int 0x80
; Print Result
push dword 1
push dword Bss_Result
push dword STDOUT
sub esp, 0x4
mov eax, SYS_WRITE
int 0x80
sub esp, 0x4
call Endl
;push dword Len_Line
;push dword Msg_Line
;push dword STDOUT
;sub esp, 0x4
;mov eax, SYS_WRITE
;int 0x80
; Exit Program
sub esp, 0x4
mov eax, SYS_EXIT
int 0x80
Result :
Enter a Digit : 3
Please Enter a Second Digit : 2
The Sum is : 5
Segmentation fault: 11
It works fine if you just write it without calling it as a function.
Why do I get an error if I implement it as a function?