NKStartup的參數KData是什么？,其實就是一個數據結構，?它位于nkldr的data區。如下：

??????AREA?|.KDATA|,DATA,NOINIT

????????

KDataArea

PTs?????%???????0x4000??????????;?space?for?first-level?page?table

ExceptionVectors?

????????%???????0x0400????;?space?for?exception?vectors

????????%???????0x0400????;?space?for?interrupt?stack

????????%???????0x0100????;?space?for?FIQ?stack

????????%???????0x0700????;?space?for?Abort?stack

KPage??%???????0x0c00???;?space?for?kernel?stack?&?KDataStruct

HighPT?%???????0x0400???;?2nd?level?page?table?to?map?0xFFF00000

KDEnd?%???????0

撇開實現，?單純去理解的話，?和傳遞一個結構體指針沒有什么區別。?再問：?這個數據結構干嘛的，代表什么？?這得明白高地址分配。

[高地址分配]

???^?0xFFFD0000

FirstPT?????????#?0x4000

?????????????#?0x4000

?????????????#?0x8000

?????????????#?0x10000???????;?not?mapped

ExVector???????#?0x0400????????;?vectors?and?table

?????????????#?0x0400??;?1K?interrupt?stack????????????(ffff0400)

IntStack???????#?0x0100?;?256?byte?FIQ?stack????????????(ffff0800)

FIQStack??????#?0x0700?;?2K-256?abort?stack????????????(ffff0900)

AbortStack??#0xC000-0x1000;not?mapped????????????????(ffff1000)

KDBase???????#?0x07E0????????;?2K-32?kernel?stack

KStack????????#?0x0020????????;?temporary?register?save?area

KData?????????#?0x400?????????;?kernel?data?area

FirstPT就是之前說的一級頁表所在。大小16kbytes。?后面保留了2塊區域，也許是提供給2級頁表使用。?ExVector是異常入口，?Arm有個機制，?通過設定p15，?可以將異常入口從0x18改成高地址FFFF0000.?IntStack，?FIQStack，?AbortStack，?KStack分別是各個模式以及內核的堆棧。?KData就是內核參數區了。

typedef?struct?ARM_HIGH?{

????ulong???firstPT[4096];??????//?0xFFFD0000:?1st?level?page?table

????char????reserved2[0x20000-0x4000];

????char????exVectors[0x400];???//?0xFFFF0000:?exception?vectors

????char????reserved3[0x2400-0x400];

????char????intrStack[0x400];???//?0xFFFF2400:?interrupt?stack

????char????reserved4[0x4900-0x2800];

????char????abortStack[0x700];??//?0xFFFF4900:?abort?stack

????char????reserved5[0x6800-0x5000];

????char????fiqStack[0x100];????//?0xFFFF6800:?FIQ?stack

????char????reserved6[0xC000-0x6900];

????char????kStack[0x800];??????//?0xFFFFC000:?kernel?stack

????struct?KDataStruct?kdata;???//?0xFFFFC800:?kernel?data?page

}?ARM_HIGH;

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