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SubjectRe: [PATCH] x86: fix virt_addr_valid() with CONFIG_DEBUG_VIRTUAL=y
On 10/01/2008 09:46 PM, Andi Kleen wrote:
>> Anyway virt_addr_valid() is IMHO wrong. E.g. first modules VM address
>> 0xffffffffa0000000 is after __pa() 200M which is valid pfn after the shift even
>> on the flatmem model with enough memory.
>>
>> Am I missing something? What's the exact purpose of the virt_addr_valid()?
>
> I think it's supposed to be only used on direct mapping anyways (judging
> from a quick look a the users)

Then kmemcheck assumes something else. Citing:
* We need to be extremely careful not to follow any invalid pointers,
* because this function can be called for *any* possible address.
and the very first check is !virt_addr_valid(address).

> So not handling text mapping is ok, but don't panic on it.

It doesn't handle properly anything but text and direct mapping. Now it
oopses/causes BUG on that wrong cases.

I think we should set it down there that it was intended to be used only on
text/direct mapping and only for checking if there is a physical memory page
behind this kind of virtual address.


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