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flat assembler > OS Construction > long mode segment protection?

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a115433



Joined: 05 Mar 2010
Posts: 144
I didnt found ANY information in manuals about it.
Why does data segment can be written to without write bit set in long mode?
when i load ds/es/fs/gs, write bit is ignored. base apply only to fs and gs, ok.

why write is ignored?
when i load SS, it require write permissions btw.
Post 19 Mar 2010, 16:48
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MazeGen



Joined: 06 Oct 2003
Posts: 953
Location: Czechoslovakia
Correct me if I'm wrong, but it turned out that paging is the usual way to protect memory in most 32-bit OS's so segment-level protection became unused. This featured 64-bit OS's.
Post 20 Mar 2010, 19:21
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a115433



Joined: 05 Mar 2010
Posts: 144
yes it suck but i care if its used. i must know.......
Post 20 Mar 2010, 19:31
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smiddy



Joined: 31 Oct 2004
Posts: 559
Empirically I don't know, when I did my 32 bit OS 5 years ago, I used the flat memory model so paging is a new thing to me, and I'm just setting up my memory map. What I would guess is that CODE type segments are much more critical to intrusion, data is not so much, so they ignore it? That would be my guess.
Post 20 Mar 2010, 20:44
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