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SubjectRe: 4GB+DEBUG_PAGEALLOC oopses with 2.6.0-test3-mm1
Ingo Molnar wrote:

>(in theory it's possible that kernel-internal mounts pass in a pointer
>where pointer + PAGE_SIZE is not a valid kernel address - if this happens
>then we'd get a hard crash.)
>
>
Exactly that happens.
I'm running with CONFIG_PAGE_DEBUG, i.e. unallocated pages are marked as
non-present in the linear mapping.

Regarding the i386 trap handler: show_registers tries to hexdump the
current instructions. It did a __get_user, to avoid causing a fault when
%eip is invalid.
Now it contains:

> if ((user_mode(regs) && get_user(c, eip)) ||
> (!user_mode(regs) && __direct_get_user(c, eip))) {
> printk(" Bad EIP value.");
> break;
> }

I.e. it's already fixed.

--
Manfred

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