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fix part of error urls
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@mudongliang
mudongliang committed Mar 15, 2018
1 parent 1917026 commit efc581b
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6 changes: 3 additions & 3 deletions Initialization/linux-initialization-1.md
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Expand Up @@ -90,7 +90,7 @@ rbp = 0x1000000 - (0xffffffff81000000 - 0xffffffff80000000)
jnz bad_address
```

在这里我们将 `rbp` 寄存器的低32位与 `PMD_PAGE_MASK` 进行比较。`PMD_PAGE_MASK` 代表中层页目录（`Page middle directory`）屏蔽位（相关信息请阅读 [paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html) 一节），它的定义如下：
在这里我们将 `rbp` 寄存器的低32位与 `PMD_PAGE_MASK` 进行比较。`PMD_PAGE_MASK` 代表中层页目录（`Page middle directory`）屏蔽位（相关信息请阅读 [paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/linux-theory-1.html) 一节），它的定义如下：

```C
#define PMD_PAGE_MASK (~(PMD_PAGE_SIZE-1))
Expand Down Expand Up @@ -162,7 +162,7 @@ NEXT_PAGE(level1_fixmap_pgt)
_PAGE_ACCESSED | _PAGE_DIRTY)
```

更多信息请阅读 [分页](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html) 部分.
更多信息请阅读 [分页](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/linux-theory-1.html) 部分.

`level3_kernel_pgt` 中保存的两项用来映射内核空间，在它的前 `510`（即 `L3_START_KERNEL`）项均为 `0`。这里的 `L3_START_KERNEL` 保存的是在上层页目录（Page Upper Directory）中包含`__START_KERNEL_map` 地址的那一条索引，它等于 `510`。后面一项 `level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE` 中的 `level2_kernel_pgt` 比较容易理解，它是一条页表项，包含了指向中层页目录的指针，它用来映射内核空间，并且具有如下的访问权限：

Expand Down Expand Up @@ -620,7 +620,7 @@ write_cr3(__pa_nodebug(early_level4_pgt));
--------------------------------------------------------------------------------

* [Model Specific Register](http://en.wikipedia.org/wiki/Model-specific_register)
* [Paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html)
* [Paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/linux-theory-1.html)
* [Previous part - Kernel decompression](http://xinqiu.gitbooks.io/linux-insides-cn/content/Booting/linux-bootstrap-5.html)
* [NX](http://en.wikipedia.org/wiki/NX_bit)
* [ASLR](http://en.wikipedia.org/wiki/Address_space_layout_randomization)
2 changes: 1 addition & 1 deletion MM/linux-mm-2.md
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Expand Up @@ -519,5 +519,5 @@ prev_map[slot] = NULL;
* [e820](http://en.wikipedia.org/wiki/E820)
* [Memory management unit](http://en.wikipedia.org/wiki/Memory_management_unit)
* [TLB](http://en.wikipedia.org/wiki/Translation_lookaside_buffer)
* [Paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html)
* [Paging](http://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/linux-theory-1.html)
* [内核内存管理第一部分](http://xinqiu.gitbooks.io/linux-insides-cn/content/MM/linux-mm-1.html)
5 changes: 2 additions & 3 deletions MM/linux-mm-3.md
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Expand Up @@ -148,7 +148,7 @@ config X86
struct my_struct *my_struct = kmalloc(sizeof(struct my_struct), GFP_KERNEL);
```
或者换句话说，在内核访问 [page](https://en.wikipedia.org/wiki/Page_%28computer_memory%29) 时会发生[缺页中断](https://en.wikipedia.org/wiki/Page_fault)。这是由于 `kmemcheck` 将内存页标记为`不存在`（关于Linux内存分页的相关信息，你可以参考[分页](https://0xax.gitbooks.io/linux-insides/content/Theory/Paging.html)）。如果一个`缺页中断`异常发生了，异常处理程序会来处理这个异常，如果异常处理程序检测到内核使能了 `kmemcheck`，那么就会将控制权提交给 `kmemcheck` 来处理；`kmemcheck` 检查完之后，该内存页会被标记为 `present`，然后被中断的程序得以继续执行下去。 这里的处理方式比较巧妙，被中断程序的第一条指令执行时，`kmemcheck` 又会标记内存页为 `not present`，按照这种方式，下一个对内存页的访问也会被捕获。
或者换句话说，在内核访问 [page](https://en.wikipedia.org/wiki/Page_%28computer_memory%29) 时会发生[缺页中断](https://en.wikipedia.org/wiki/Page_fault)。这是由于 `kmemcheck` 将内存页标记为`不存在`（关于Linux内存分页的相关信息，你可以参考[分页](https://0xax.gitbooks.io/linux-insides/content/Theory/linux-theory-1.html)）。如果一个`缺页中断`异常发生了，异常处理程序会来处理这个异常，如果异常处理程序检测到内核使能了 `kmemcheck`，那么就会将控制权提交给 `kmemcheck` 来处理；`kmemcheck` 检查完之后，该内存页会被标记为 `present`，然后被中断的程序得以继续执行下去。 这里的处理方式比较巧妙，被中断程序的第一条指令执行时，`kmemcheck` 又会标记内存页为 `not present`，按照这种方式，下一个对内存页的访问也会被捕获。
目前我们只是从理论层面考察了 `kmemcheck`，接下来我们看一下Linux内核是怎么来实现该机制的。
Expand Down Expand Up @@ -422,13 +422,12 @@ Links
* [memory leaks](https://en.wikipedia.org/wiki/Memory_leak)
* [kmemcheck documentation](https://www.kernel.org/doc/Documentation/kmemcheck.txt)
* [valgrind](https://en.wikipedia.org/wiki/Valgrind)
* [paging](https://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html)
* [page fault](https://en.wikipedia.org/wiki/Page_fault)
* [initcalls](https://xinqiu.gitbooks.io/linux-insides-cn/content/Concepts/initcall.html)
* [opcode](https://en.wikipedia.org/wiki/Opcode)
* [translation lookaside buffer](https://en.wikipedia.org/wiki/Translation_lookaside_buffer)
* [per-cpu variables](https://xinqiu.gitbooks.io/linux-insides-cn/content/Concepts/per-cpu.html)
* [flags register](https://en.wikipedia.org/wiki/FLAGS_register)
* [tasklet](https://xinqiu.gitbooks.io/linux-insides-cn/content/Interrupts/interrupts-9.html)
* [Paging](https://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/Paging.html)
* [Paging](https://xinqiu.gitbooks.io/linux-insides-cn/content/Theory/linux-theory-1.html)
* [Previous part](https://xinqiu.gitbooks.io/linux-insides-cn/content/MM/linux-mm-2.html)

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