code:clearseg - ikarishinjieva/unixV6-code-analyze-chs GitHub Wiki

0674 /* ------------------------- */

0675 .globl _clearseg

0676 _clearseg:

0677 mov PS,-(sp)

0678 mov UISA0,-(sp)

PS UISA0 保护入栈

UISD0 将在0681 保护入栈

以上将在0689 还原

0679 mov $30340,PS

置 PS

处理机优先级置 7，关中断

先前态置用户态

当前态置核心态

0680 mov 6(sp),UISA0

UISA0 ← i

0681 mov UISD0,-(sp)

0682 mov $6,UISD0

UISD0 ← 6
置段为可读写

0683 clr r0

0684 mov $32.,r1

0685 1:

0686 clr -(sp)

0687 mtpi (r0)+

0688 sob r1,1b

将第i块64字节置零

0689 mov (sp)+,UISD0

0690 mov (sp)+,UISA0

0691 mov (sp)+,PS

0692 rts pc

0693