Capisimizing wall(1)

[hanslu952_gmail.com]

Summary

The first problem is to use pdfork.
because fork() is disallowed in capability mode,
we use pdfork() to replace ,the semantic is same as rwhod
The second problem is to limit the file descriptor used by open.
it sets up a specific right (write) for a file descriptor and then
attempts to enforce the limitation. If the operation fails,
the program will terminate with a specific error message

Test Plan

	   ktrace wall
	   kdump ktrace.out

[hanslu952_gmail.com]

Closed Revision