[Lguest] Why lguest is running __PAGE_OFFSET too low?
Rusty Russell
rusty at rustcorp.com.au
Thu Apr 11 13:03:49 EST 2013
Guillaume Thouvenin <guillaume.thouvenin at polymtl.ca> writes:
> Hello,
>
> I'm currently doing the quest and there is something that I don't
> understand when the guest started. In lguest_entry(), it is said that
> lguest is running __PAGE_OFFSET too low.
(Oops, dug this out...)
Page tables aren't set up yet. The kernel is loaded at *physical*
address 0, and then maps itself to __PAGE_OFFSET.
This is how the non-lguest boot code works too.
> I see that lguest is not
> running in kernel space like it should be because it is loaded by the
> launcher that allocates the memory somewhere in userspace. Thus I
> thought that the guest is running "launcher offset" too low. I
> apologize if the question has already been asked but I didn't find
> where in the archive we can search.
This feedback is good, I'll update the documentation...
> Thanks to Rusty for the quest, it is really awesome :)
You're welcome! If you finished it, you'll know I owe you a beer :)
Hope that helps!
Rusty.
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