The 386 supports four privilege rings (0 through 3), though in practice nearly all operating systems use just two: ring 0 for the kernel and ring 3 for user programs. Three privilege levels interact on every segment access: CPL (Current Privilege Level), DPL (Descriptor Privilege Level), and RPL (Requested Privilege Level).
With that’s being said, let’s jump right in.
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这种方法通过类型别名和转换器封装了平台差异，避免了平台侧重复编写转换逻辑。
Integrate Facebook Messenger directly with your website, including chat history and recent interactions for a fluid customer service experience