Linux内核：进程页表驻留在哪里？
由于仅由内核使用，因此它们只能位于 PAGE_OFFSET 以上的地址中。但我正在阅读 this 页面及其末尾（在 IRC 会议中）我读到以下几行，这让我很困惑：
saxm> riel: so where do page tables reside? Surely not below PAGE_OFFSET? Somewhere above PAGE_OFFSET+896mb then?
riel> they could reside anywhere
saxm> anywhere from 0->4gb (on x86 with no pae)?
riel> saxm: yeah
我的意思是，为什么它们会位于 PAGE_OFFSET 下面？如果是这种情况，用户空间进程是否无法访问它们？
Being used only by the kernel, they should only lie in the addresses above PAGE_OFFSET. But I was reading this page and at the end of it (in the IRC convo) I read the following lines which really confused me:
saxm> riel: so where do page tables reside? Surely not below PAGE_OFFSET? Somewhere above PAGE_OFFSET+896mb then?
riel> they could reside anywhere
saxm> anywhere from 0->4gb (on x86 with no pae)?
riel> saxm: yeah
I mean, why would they lie below PAGE_OFFSET? Wouldn't user space processes be able to access them if that is the case?
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我认为瑞尔想说的是它们（几乎）可以驻留在物理内存中的任何地方——没有固定的映射。
页表映射在内核虚拟地址空间中（即在 PAGE_OFFSET 之上），并且对用户空间不可见（正如您指出的那样，这是有道理的，因为我们不希望用户破坏自己的页表）。
看看这个相关帖子：
Linux 是否对页面目录使用自映射？页表？
I think what riel was trying to say is that they can reside (almost) anywhere in physical memory--there's not a fixed mapping.
Page tables are mapped in the kernel virtual address space (i.e. above PAGE_OFFSET), and are invisible to user space (which, like you point out, makes sense because we wouldn't want users clobbering their own page tables).
Take a look at this related post:
Does Linux use self-map for page directory and page tables?