Re: bisected boot regression post 2.6.25-rc3.. please revert

From: H. Peter Anvin
Date: Mon Mar 03 2008 - 17:59:49 EST


Segher Boessenkool wrote:
so (on 32-bit) ~_PAGE_PSE is ~0x80L is 0xffffff7f, which when cast to
64-bit is 0x00000000ffffff7f,

Actually, it is signed, so this isn't true. Comments about unsafeness
still apply.

It turns out that PAGE_SIZE is unsigned. So this gives us for

(~PAGE_MASK & ~_PAGE_USER & ~_PAGE_PSE & ~_PAGE_NX)

the types UL, L, L, ULL resp.

The associativity of & is left-to-right, so this in turn becomes

UL, L, ULL

UL, ULL

ULL

and that cast from UL to ULL doesn't sign-extend.


All the masks either need to be the proper size or signed.

-hpa
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