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Fix nit in Paging file

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Dan Robertson 8 months ago
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      Theory/linux-theory-1.md

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Theory/linux-theory-1.md View File

@@ -80,7 +80,7 @@ These fields have the following meanings:

* Bits 63:52 - reserved must be 0.
* Bits 51:12 - stores the address of the top level paging structure;
* Reserved - reserved must be 0;
* Bits 11: 5 - reserved must be 0;
* Bits 4 : 3 - PWT or Page-Level Writethrough and PCD or Page-level cache disable indicate. These bits control the way the page or Page Table is handled by the hardware cache;
* Bits 2 : 0 - ignored;

@@ -95,7 +95,7 @@ schematically, we can imagine it like this:

![4-level paging](http://oi58.tinypic.com/207mb0x.jpg)

Every access to a linear address is either a supervisor-mode access or a user-mode access. This access is determined by the `CPL` (current privilege level). If `CPL < 3` it is a supervisor mode access level, otherwise it is a user mode access level. For example, the top level page table entry contains access bits and has the following structure:
Every access to a linear address is either a supervisor-mode access or a user-mode access. This access is determined by the `CPL` (current privilege level). If `CPL < 3` it is a supervisor mode access level, otherwise it is a user mode access level. For example, the top level page table entry contains access bits and has the following structure (See [arch/x86/include/asm/pgtable_types.h](https://github.com/torvalds/linux/blob/16f73eb02d7e1765ccab3d2018e0bd98eb93d973/arch/x86/include/asm/pgtable_types.h) for the bit offset definitions):

```
63 62 52 51 32

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