Segmentation fault after function call in x86 assembly - debugging

Question

I'm currently writing a compiler and I have created some tests and only one of them fails with Segmentation fault (core dumped) as error message.
This is the code that gets compiled
function main(): int {
var f: int = 10;
return func(f) - func(f / 2);
}
function func(a: int): int {
return a;
}
And this is the generated assembly code (it's not really optimized as you can see)
section .text
global _start
_start:
call function_main
mov rdi, rax
mov rax, 60
syscall
global function_main
function_main:
push rbp
mov rbp, rsp
sub rsp, 4
mov rax, 10
mov DWORD[rbp-0], eax
mov eax, DWORD[rbp-0]
mov rdi, rax
call function_func
push rax
mov eax, DWORD[rbp-0]
mov rbx, 2
idiv rbx
mov rdi, rax
call function_func
mov rbx, rax
pop rax
sub rax, rbx
mov rsp, rbp
pop rbp
ret
global function_func
function_func:
push rbp
mov rbp, rsp
sub rsp, 4
mov DWORD[rbp-0], edi
mov eax, DWORD[rbp-0]
mov rsp, rbp
pop rbp
ret
The assembly file is compiled with nasm -f elf64 ./test9.lv.asm -o ./test9.lv.asm.o and ld -g ./test9.lv.asm.o a.out
I've used gdb to debug the binary file and it seems like the program receives the SIGSEGV signal right after func(f) returns the first time.
But now I don't know why this is happening in this case.