#define SIGNATURE ((uint32_t) (0xd9 | (0x74 << 8) | (0x24 << 16) | (0xf4 << 24))

static int check_fnstenv_instr(uint8_t* buf, int buf_len, int offset)
{
        for (buf += offset, buf_len -= offset - 3; buf_len > 0; buf_len--)
            if (*((uint32_t*)buf++) ==  SIGNATURE)
                return $MATCH$;
        return $NO MATCH$;
}