Re: Some questions
Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> wrote:
> On Thu, Oct 28, 1999 at 12:58:10PM +0200, Gergely, Zsombor wrote:
> > 2) You say it is good to put the servers in user space. Is it the same as user
> > space vs. kernel space? If I understand well, the separation provides memory
> > protection as well (crashes, garbage in memory). If yes, don't you loose
> > something with not separating?
> Yes indeed. It user/kernel space with all protections you want in the user
> level and no protection in the kernel level. I don understand your question,
> though. What should we seperate?
I'd guess he's referring to the fact that kernel services run in a
different address space from the processes that use them. This is the
case with Hurd servers even more than with a monolithic kernel,
because there are three address spaces involved in a typical system
call - application, microkernel, and server. This three-way
separation should provide even better protection from system crashes
than the simple user/kernel model.