Messages in this thread | | | Date | Mon, 14 Jan 2008 23:23:49 +0100 | From | Andi Kleen <> | Subject | Re: unify pagetable accessors patch causes double fault II |
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> OK, I see the problem. The problem is that the _PAGE_X defines are > defined with _AC(UL, 1 << _PAGE_BIT_X), which has unsigned long type. > This means that ~_PAGE_X also has unsigned long type, and so when cast > to 64-bit in pte_mkX, it ends up &ing the pte with 0x00000000ffffffxxx, > with predictable results.
Actually I fixed some of that -- see the pgtable-nx patch on firstfloor -- but it still doesn't work. Or maybe my patch was not complete. > > The original code just used signed constants for the _PAGE_X > definitions, which will sign-extend when cast to 64-bit, and so have the > upper bits set when masking. (Well, actually, the old code just > operated on pte_low, so the problem didn't arise; however, pgtable_64.h > also uses integers for its _PAGE_X, which has the same sign-extended > 32->64 casting property). > > I'll put together a fixup patch now.
I'm leaving now but can test later.
-Andi
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