Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!microsoft!edwardj From: edwardj@microsoft.UUCP (Edward JUNG) Newsgroups: comp.sys.mac.system Subject: Re: Protected-mode snake oil Message-ID: <56610@microsoft.UUCP> Date: 16 Aug 90 02:24:16 GMT References: <1204.26c2fb48@waikato.ac.nz> <1210.26c694ed@waikato.ac.nz> <8099@jarthur.Claremont.EDU> Reply-To: edwardj@microsoft.UUCP (Edward JUNG) Organization: Microsoft Corp., Redmond WA Lines: 47 In article <8099@jarthur.Claremont.EDU> wilkins@jarthur.Claremont.EDU (Mark Wilkins) writes: [quotes deleted] > You're obviously missing the point. What he meant to point out is that in >a protected-mode environment it is very difficult for a user process to >directly patch operating system calls, and he is arguing that the capability >makes the Macintosh a much more easily customizable system. > No doubt that a non-protected environment is more easily hacked than a protected environment, where "hacked" here means "made to do things on behalf of ALL apps that the architecture did not originally allow". By definition non-protected systems are going to provide fewer hinders to hacking about, passing pointers among processes to share memory, writing into other processes' memory spaces, hooking the entire OS from under all apps, etc. You have to balance this against the flexibility of a virtual machine. Unix, for example, has been made to do quite a few things considering its 1960's heritage, and it too is a protected system. While Unix isn't exactly a VM, it is, for all intents and purposes, highly abstracted. Not as open as a non-protected system, but still quite able. And much safer. Newer OS that move more responsibility to user code allow a large degree of flexibility, even down to user-code VM pagers. The NeXT machine, for example, allows user code to do all those Mac-like things in a protected environment. > Note that I'm not sure how I feel about that argument, but you weren't >answering his point. > >-- Mark Wilkins > wilkins@jarthur.claremont.edu I don't think the point washes: that protected systems make useful tools *too* difficult to develop is untrue IMHO (note the "too"). Note: I am biased because my fx blew up on Monday and hosed alot of work. Multifinder has made the amount of potentially lost work much greater. I, for one, want a protected environment. Under OS/2, SunOS, or NeXT I may lose data in one crashing app, but virtually never all the running applications. This becomes more critical as machines become depended- upon for services or network-linked documents. Edward Jung Advanced Systems Architecture Systems Strategist Microsoft Corporation