disabling kernel access to memory

Mike Kravetz kravetz at us.ibm.com
Tue Aug 17 09:48:16 EST 2004

On Mon, Aug 16, 2004 at 12:00:31PM -0700, Dave Hansen wrote:
> That shouldn't be too hard.  This is for debugging anyway, right Mike?
> Put a check in the htab_pte_insert() (or whatever the hardware insertion
> call) is to scream if you attempt to set a hardware pte to one of the
> empty areas.  Then go kill all the Linux ptes, effectively (if these
> were real functions (you shouldn't have to do this anyway if all of the
> pages from that area are out of the allocator):
> 	for_each_task()
> 		for_each_pgd()
> 			for_each_pmd()
> 			...
> Then, kill the kernel mappings.

Thanks, I'll give that a try.

> > Back in my userspace days I remember threading libraries liked to use
> > mprotect for such things.  Linux kernel has mprotect and sys_mprotect,
> > not sure if they will fit your needs or not.
> Those only apply to userspace pages.  I think Mike want to make sure to
> kill all accesses to the memory, including from the kernel.

Yeah, I'm mostly/only interested in access from the kernel.

Right now, I'm slowly finding places in the kernel that assume the
phys -> virt translations are linear.  When I can get a kernel to
boot where the translations are nonlinear, then I'll look into the
debug stuff.


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