Re: A question aboout virtual mapping of kernel and module pages

[Matvejchikov Ilya <matvejchikov@gmail.com>]

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Hi Vladimir,

Thanks for the suggestion, but the problem was not in mapping itself. I've
been mistaken
about
it
as
the problem I've had was related to bug in my code. Thanks for the idea to
check if I-D cache aliasing happens. It turns me to the
right
direction :)

2013/12/20 Vladimir Murzin <murzin.v@gmail.com>

> Hi Ilya!
>
> On Fri, Dec 20, 2013 at 12:25:13AM +0400, Matvejchikov Ilya wrote:
> > I'm using VMAP function to create memory writable mapping as it
suggested
> > in ksplice project. Here is the implementation of map_writable function:
> > ...
> >
> > This function works well when I used it to map kernel's text addresses.
All
> > fine and I can rewrite read-only data well via the mapping.
> >
> > Now, I need to modify kernel module's text. Given the symbol address
inside
> > the module, I use the same method. The mapping I've got seems to be
valid.
> > But all my changes visible only in that mapping and not in the module!
> >
> > I suppose that in case of module mapping I get something like
copy-on-write
> > but I can't prove it.
> >
>
> Looks like I-D cache aliasing... Have you flushed cashes after your
> modifications were done?
>
> Vladimir
>
> > Can anyone explain me what's happend and why I can use it for mapping
> > kernel and can't for modules?
> >
> >
http://stackoverflow.com/questions/20658357/virtual-mapping-of-kernel-and-module-pages

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