Segmentation: Difference between revisions
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*In general if you want to use the segmentation mechanism, by having the different segment registers represent segments with different base addresses, you won't be able to use a modern C compiler, and may very well be restricted to just Assembly. |
*In general if you want to use the segmentation mechanism, by having the different segment registers represent segments with different base addresses, you won't be able to use a modern C compiler, and may very well be restricted to just Assembly. |
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*So, if you're going to use C, do what the rest of the C world does, which is set up a flat-memory model, use paging, and ignore the fact that segmentation even exists. |
*So, if you're going to use C, do what the rest of the C world does, which is set up a flat-memory model, use paging, and ignore the fact that segmentation even exists. |
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==Notes Regarding Pascal[FPC]== |
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Above may apply in theory to FreePascal, however, in reality is ignored, if the compiler at all pays any attention to same. |
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The twin segments for CODE and DATA are used, and as specified above,therefore, required.Size limits, however, are respected.(does NOT have to be 4GB in length) |
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"*In general if you want to use the segmentation mechanism, by having the different segment registers represent segments with different base addresses, you won't be able to use a modern C compiler, and may very well be restricted to just Assembly." |
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This is simply NOT true for Freepascal. |
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The 'A in A:B' is what allows 48 and 64 bit pointer references, not only with Pascal's NewFrontier unit, but FreePascal as well(Word:Longint Pointer reference). |
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*Assumption of CODE and DATA occupying the same space, (at least with PAE NX bits and Paging units not used) allows ROGUE/virus like code in the first place to take advantage of the machine. INTEL Specs even say this. CODE and DATA must be KEPT separate. Microsoft still is plagued with this problem,despite having NX bits enabled even in the latest OSes. |
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==See Also== |
==See Also== |
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