Messages in this thread | | | Subject | Re: [patch 02/02] Debug option to write-protect rodata: the write protect logic and config option | From | Arjan van de Ven <> | Date | Fri, 11 Nov 2005 10:47:07 +0100 |
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> people objecting to that. > > > > (It's not clear cut: while the last bit of the kernel no longer is > > covered by a 2Mb tlb, most intel cpus have very few of such tlbs in the > > first place and this would free up one such tlb for other things (say > > the stack data) or even the userspace database), so it's not all that > > clear cut what the cost of this is) > > I'm dumb. But how is "the last bit of the kernel no longer is covered > by a 2Mb tlb"? Could you explain a bit more?
in memory it'll look something like this
0 2 4 6 -- kernel text -- + -- kernel text -- + --- k. text-- rodata -- + --
normally the range from 0 to 6 is covered with 2Mb tlb's. Now to make rodata read only, the hugetlb entry covering 4-6 Mb range needs to be split into 4Kb entries, so that the rodata portion can have different permissions than the rest of that range.
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