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ok guys I and my friend are trying to write an operatingsystem and were going through the code of linux MM and discovered that linux used the same virtual space
i.e only one page directory for all its processes including the kernel space. though there is segment level protection in this approach we are leaning towards a seperate page directory for each process giving obvious page level protection too and it makes it way easier to deal with page replacement algorithms. which do u think is better the linux approach or ours and which do u think is easier. Please give your views on this subject any criticism is also most welcome.

only one page directory in Linux ? i guess you're not reading the latest kernel, then, because in the code for thread switch i saw from Linux, there was a "mov cr3, [next_thread->process->CR3_copy], or something alike ...

moreover, i know Linux uses copy on write, which seems hard to set up without paging ... and finally, i don't think there's that much segmented protection because it isn't even possible for it to discover you're executing something that is on the stack.