Function getrandom 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn getrandom(
    buf: *mut c_void,
    buflen: size_t,
    flags: c_uint,
) -> ssize_t

See https://www.man7.org/linux/man-pages/man2/getrandom.2.html.

Fills the buffer pointed to by buf with up to buflen random bytes.