Curiosity killed the cat


(Benjamin Bell) #1

So the way I understand it, segmentation was never really a thing. Intel and others came up with these segment registers that were meant to be used by the OS guys to index the GDT or LDT. From there they’d get a descriptor that had a base and a limit for the segment and a couple of control bits like Type that would be used to set a segment as code or data and the rwx. Instead OS guys decided to enforce permissions using paging and leave memory looking like one blob from a segmentation perspective.

Why call it a segmentation fault when it is really a page fault?

Why did nobody go with the segmentation idea that the hardware guys were pushing? Other than the fact that intel only had 6 segment registers.


(Geoffrey Challen) #2

Segments can still be an OS concept even if they aren’t supported in hardware. It’s a nice organizational principle to have a memory region with similar permissions, than can be shared between multiple processes, etc. Different operation systems now have different terminology for them.