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回复 1# weichuang02
由于CPU的兼容性问题Ｗindows只使用两个级别的，如Alpha处理器和SGI MIPS都只有两个级别。Windows Internals这本书里有讲原话如下：
The architecture of the x86 and x64 processor defines four privilege levels, or rings, to
protect system code and data from being overwritten either inadvertently or maliciously by
code of lesser privilege. Windows uses privilege level 0 (or ring 0) for kernel mode and privilege
level 3 (or ring 3) for user mode. The reason Windows uses only two levels is that some hardware
architectures that were supported in the past (such as Compaq Alpha and Silicon Graphics MIPS)
implemented only two privilege levels
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发表于 2012-07-12 09:51
发表于 2013-09-18 14:38