Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!sdd.hp.com!news.cs.indiana.edu!ux1.cso.uiuc.edu!news.iastate.edu!kickapoo.cs.iastate.edu!hamilton From: hamilton@kickapoo.cs.iastate.edu (Jon Hamilton) Newsgroups: comp.sys.mac.programmer Subject: Re: System 7.0/Supervisor Mode ? Message-ID: Date: 16 May 91 06:22:27 GMT References: <1991May15.024320.9727@world.std.com> <1991May15.155912.23810@cbnewsk.att.com> <1991May16.043539.25316@world.std.com> Sender: news@news.iastate.edu (USENET News System) Organization: Iowa State University, Ames IA Lines: 30 siegel@world.std.com (Rich Siegel) writes: >In article <1991May15.155912.23810@cbnewsk.att.com> ech@cbnewsk.att.com (ned.horvath) writes: >>have made sure ThC and ThP won't generate privileged instructions, and that >>all that hand-coded library asm code is clean (right, Rich?), but not all >>of us know for sure...! > In fact, it's not that the compilers generate or are written with >privileged instructions; it's that the debuggers need to handle exceptions, >and when the machine runs in user mode, there is additional work that's >necessary. It's not that difficult to go from user to supervisor mode if you know what the stack looks like. I don't see what all the hubub is about - why would anyone care which mode they were in? All a debugger would have to do is put a jmp in the memory location pointed to by the exception jump table - no supervisor mode needed for that. Again, though, _who cares_? >R. >-- >----------------------------------------------------------------------- >Rich Siegel Internet: siegel@world.std.com >Software Engineer Applelink: SIEGEL >Symantec Languages Group -- Jon Hamilton hamilton@kickapoo.cs.iastate.edu " I feel a lot more like I do now that I did before I got here " - can't remember who