I386 segmentation highlights

By: Michael S (already5chosen.delete@this.yahoo.com), October 5, 2021 11:27 am
Room: Moderated Discussions
sr (nobody.delete@this.nowhere.com) on October 5, 2021 11:16 am wrote:
> rwessel (rwessel.delete@this.yahoo.com) on October 4, 2021 4:57 pm wrote:
>
> > How does any of that help? You still need to pass pointers to
> > both areas around with limited ability to distinguish the users.
>
> Segmentation done fully has some obvious benefits but it's also obvious that it will inevitable complicate
> programming. So Intel did design it's segmentation so that some segmentation without any effort is possible,
> to use segmentation only to hardware divide stack from other data area in flat address range.
>
> And as it is done with stack in expand-down segment with inverted addressing(from top address to bottom)
> with expand up data segment with normal addressing so that way configured segmented addressing is basically
> 100% same as with without segmentation at all with usual memory allocation - stack to top of addressing
> and data in bottom so they grow towards each others. With segmentation it still retains hardware boundary
> between stack and other data - at some time it was thought as important thing to have.
>

I don't see how even that little is going to work without complicating your programming environment either with "far" pointers or with non-interchangeable "data" and "stack" pointers.
That is, in theory compiler can classify pointer parameters by doing comparison against segment limit at run time and convert "near" pointers to "far" pointers on the fly, but performance cost of such arrangement would be even higher that simply making all pointers "far".

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                                                      I386 segmentation highlightssr2021/10/04 06:53 AM
                                                        I386 segmentation highlightsAdrian2021/10/04 08:53 AM
                                                          I386 segmentation highlightssr2021/10/04 09:19 AM
                                                        I386 segmentation highlightsrwessel2021/10/04 03:57 PM
                                                          I386 segmentation highlightssr2021/10/05 10:16 AM
                                                            I386 segmentation highlightsMichael S2021/10/05 11:27 AM
                                                            I386 segmentation highlightsrwessel2021/10/05 03:20 PM
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                                                Or use a PLBdmcq2021/09/28 06:45 AM
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                  Multi-threading?---2021/09/10 08:19 AM
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                            Virtually tagged L1-cachessr2021/09/20 03:11 AM
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      Virtually tagged L1-cachesLinus Torvalds2021/09/08 11:34 AM
        Virtually tagged L1-cachesdmcq2021/09/09 01:46 AM
          Virtually tagged L1-cachesdmcq2021/09/09 01:58 AM
          Virtually tagged L1-cachessr2021/09/11 12:29 AM
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    Where do you see this information? (NT)anon22021/09/09 01:45 AM
      Where do you see this information?sr2021/09/11 12:40 AM
        Where do you see this information?anon22021/09/11 12:53 AM
          Where do you see this information?sr2021/09/11 01:08 AM
            Thank you (NT)anon22021/09/11 03:31 PM
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