Review assembly strdup reimplementation

Question

I am posting a message here because I am new to assembly programming. My goal today was to recode a strdup in assembler, so to save my first parameter which is a string (const char*), I have doubts when handling the RSP to reserve space for the string and how I reset it at the end.

However I'm not sure I did well, and I would like to have a review, and advice on what I could improve. Thanks in advance !

extern malloc
extern _ft_strlen
extern _ft_strcpy

section .text
    global  _ft_strdup

_ft_strdup:
        push        rbp                   ; prologue                      
        mov         rbp, rsp              ; prologue           
        sub         rsp, 8                ; reserve space for string                   
        mov         qword [rbp - 8], rdi  ; put first param on the stack
        call         _ft_strlen           ; strlen the first param
        mov         rdi, rax              ; put return value on the rdi register                       
        call        malloc                ; malloc rdi bytes                        
        cmp         rax, 0                ; check if malloc failed                                
        je          exit_prog                               
        mov         rdi, rax              ; put malloc address in rdi  (DEST)                            
        mov         rsi, qword [rbp - 8]  ; put source address in rsi (SRC)
        call        _ft_strcpy            ; copy                 
        add         rsp, 8                ; reset                     
        pop         rbp                   ; epilogue                             
        ret

exit_prog:
        xor             rax, rax
        add             rsp, 8                   
        pop             rbp                                     
        ret