@#include "sched.h"#define 	PID_OFT		0#define	STATE_OFT		4#define	COUNT_OFT		8#define	PRIORITY_OFT	12#define	CONTENT_OFT		16@ 應該轉換成虛擬地址	#define	SDRAM_BASE		0x30000000#define	SDRAM_SIZE		0x04000000				@ 寄存器切換@ __switch_to(struct task_struct pcur,struct task_struct pnext):	@ r0 = &pcur, r1 = &pnext@ 對于linux,__switch_to在arch/arm/kernel/entry-armv.S中定義,以下代碼參考它			@ ENTRY(__switch_to).global __switch_to__switch_to:			add	r0, r0,#CONTENT_OFT	ldr	sp, =(SDRAM_BASE+0x100000-14*4)	stmia	r0!,{sp}^		@ 用戶/系統模式下的sp	mrs	r2, spsr		@ 讀出spsr，保存	stmia	r0!,{r2}	ldmia	sp!,{r2-r8}		@ 把進入中斷時保存的寄存器轉移到當前task struct中	stmia	r0!,{r2-r8}	ldmia	sp!,{r2-r8}	stmia	r0!,{r2-r8}	ldr	r0, [r1,#PID_OFT]	@ 要切換到的進程的PID	mov	r0, r0, lsl #25	@ PID存在寄存器的最高7位		mcr	p15, 0, r0, c13, c0, 0	@ 寫next_pid,從此，VA<32M的取址計算公式就變了，不過現在的VA總是大于32M的	add	r1, r1, #CONTENT_OFT	@ r1 = &task[next].content	ldmia	r1!,{sp}^		@ 用戶/系統模式下的sp		ldmia	r1!,{r2}		@ spsr	msr	spsr_cxsf, r2	mov	sp, r1			ldmia	sp!,{r0-r12,pc}^	@ 模擬中斷返回, ^表示將spsr的值復制到cpsr