Re: [discuss] Re: [PATCH] [3/4] i386: Fix overflow in e820_all_mapped

[Arjan van de Ven <arjan@infradead.org>]

On Fri, 2006-04-28 at 09:07 +0200, Jan Beulich wrote:
> >>> Linus Torvalds <torvalds@osdl.org> 28.04.06 07:39 >>>
> >
> >
> >On Fri, 28 Apr 2006, Andi Kleen wrote:
> >> 
> >> The 32bit version of e820_all_mapped() needs to use u64 to avoid
> >> overflows on PAE systems.  Pointed out by Jan Beulich
> >
> >I don't think that's true.
> >
> >It can't be called with 64-bit arguments anyway. If the base address 
> >doesn't fit in 32-bit, we'd be screwed in other places, afaik.
> 
> The arguments don't necessarily need to be u64, but (at least some of)
> the calculations inside the function do. Otherwise, a region starting
> below 4G and extending to or beyond 4G would not be considered
> correctly.

since this is use-once __init code I rather keep it simple and safe (eg
use u64) than do complex tricks to make it safe in another way.. and the
4G thing is a real potential problem that's easily fixed with the u64
thing.

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