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Update Booting/linux-bootstrap-2md.md

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hailin cai
2016-02-23 15:20:31 -05:00
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@@ -358,19 +358,23 @@ ENDPROC(memset)
到这里位置，全局堆就被正确初始化了。在全局堆被初始化之后，我们就可以使用`GET_HEAP`方法。至于这个函数的实现和使用，我们将在后续的章节中看到。
CPU validation
检查CPU类型
--------------------------------------------------------------------------------
The next step as we can see is cpu validation by `validate_cpu` from [arch/x86/boot/cpu.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/cpu.c).
在堆栈初始化之后，内核代码通过调用[arch/x86/boot/cpu.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/cpu.c)提供的`validate_cpu`方法检查CPU类型以确定系统是否能够在当前的CPU上运行。
`validate_cpu`调用了[`check_cpu`](https://github.com/torvalds/linux/blob/master/arch/x86/boot/cpucheck.c#L102)方法得到当前系统的CPU级别，并且和系统预设的最低CPU级别进行比较。如果不满足条件，则不允许系统运行。function and passes cpu level and required cpu level to it and checks that the kernel launches on the right cpu level.
It calls the [`check_cpu`](https://github.com/torvalds/linux/blob/master/arch/x86/boot/cpucheck.c#L102) function and passes cpu level and required cpu level to it and checks that the kernel launches on the right cpu level.
```c
/*from cpu.c*/
check_cpu(&cpu_level, &req_level, &err_flags);
if (cpu_level < req_level) {
...
printf("This kernel requires an %s CPU, ", cpu_name(req_level));
printf("but only detected an %s CPU.\n", cpu_name(cpu_level));
return -1;
}
```
`check_cpu` checks the cpu's flags, presence of [long mode](http://en.wikipedia.org/wiki/Long_mode) in case of x86_64(64-bit) CPU, checks the processor's vendor and makes preparation for certain vendors like turning off SSE+SSE2 for AMD if they are missing, etc.
Memory detection