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Experimental KPTI Support For x86 32-bit Linux

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  • Experimental KPTI Support For x86 32-bit Linux

    Phoronix: Experimental KPTI Support For x86 32-bit Linux

    For the Kernel Page Table Isolation (KPTI) support currently within the Linux kernel for addressing the Meltdown CPU vulnerability it's currently limited to 64-bit on the x86 side, but for the unfortunate souls still running x86 32-bit operating systems, SUSE is working on such support...

    http://www.phoronix.com/scan.php?pag...t-PTI-RFC-SUSE

  • #2
    Since PCIDs will (probably?) not be available, I wonder whether it would make sense to unmap the kernel memory from the page tables (minus a stub for those bits which are still needed) when switching to user mode rather than doing a full CR3 page-table switch. That way at least the user memory TLB entries should still stay valid.

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    • #3
      32b x86 has already been quite unsafe for web browsing for a while. E.g. aslr doesn't help too much. Does anyone use such legacy hardware online anymore?

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      • #4
        I wonder if this will have the effect of increasing the userland VA address space to 4GB (minus just a tiny bit).

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        • #5
          Originally posted by caligula View Post
          32b x86 has already been quite unsafe for web browsing for a while. E.g. aslr doesn't help too much. Does anyone use such legacy hardware online anymore?
          When even Steam survey shows about 2% 32bit used, it won't surprises me that in some areas of the world it is used up to 10 times more than that say up to 20% On Debian popcon survey, it currently shows about 11% 32bit and year before it was about 14% - surely it goes down, but that is still not nothing nor enough as ditchero census There, it is only 5 years how 64bit surprases 32bit OS installs.

          I think up to about 3 years more are needed, so that we clearly say OK now no one care about 32bit Likely Debian 10 will release 32bit OS, but won't be LTS (probably even 9 won't) and that might be probably final Or say for Debian 11 to not be release blocker and finaly in times of Debian 12 it will go to ports.

          Since Windows 10 32bit offer support up to the october of 2020, but not extended one i guess sweet spot will be year 2021.

          Nvidia also maintain 32bit OS drivers up to the end of Windows 7 cycle which is january 2020., so probably that is about it - in 2020. would be hard and in 2021. hopefully "nothing" and time when we can officialy clam 32bit OS clearly *unsupported*

          After that is after life It will be similar like XP this post 32bit era, there will be still someone who will found a way to use it even as unsupported
          These 32bit supercentenarians will probably touch year 2025.
          Last edited by dungeon; 01-19-2018, 01:13 PM.

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          • #6
            Apparently grsecurity had a fix for this whole issue on 32 bits for over 10 years (kind of, 4 line changes were needed).

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            • #7
              Originally posted by GreenByte View Post
              Apparently grsecurity had a fix for this whole issue on 32 bits for over 10 years (kind of, 4 line changes were needed).
              Link?

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              • #8
                Originally posted by kobblestown View Post
                I wonder if this will have the effect of increasing the userland VA address space to 4GB (minus just a tiny bit).
                that was also what I was wondering when the initial bug report and changes came up, ...

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                • #9
                  Originally posted by caligula View Post
                  32b x86 has already been quite unsafe for web browsing for a while. E.g. aslr doesn't help too much. Does anyone use such legacy hardware online anymore?
                  There must still be quite a few 32-bit x86 machines in use. Anyone have a handy link to stats? (Steam? Browser stats? Not sure!)

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                  • #10
                    Originally posted by duby229 View Post

                    Link?
                    It's on their twitter

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