On 2/8/08, Andi Kleen <andi@firstfloor.org> wrote:
Yes, this is true. Then our task is to make sure that this memory is
never allocated from tracked caches. We do have some changes in this
area, for instance we never track task structs. Keep in mind that only
slab objects are tracked currently, so things like stacks never catch
page faults. I am not sure if this is exactly what you had in mind,
but I don't know other kernel code very well enough to come up with
perhaps more relevant examples :-)
For now, I am simply assuming that we never load task segments, GDTs,
LDTs, or paging structures from tracked memory (e.g. regular
kmalloc()).
The problem with these instructions is not that they take page faults,
but that kmemcheck doesn't know how to handle them. Kmemcheck needs to
parse the instruction stream at EIP to determine what addresses were
accessed, their size, and the type (read or write). This can be done
currently with surprisingly little amounts of code.
But AFAIK the format for MMX and SSE is different from the "regular"
instructions, and so I don't know how to parse them. But this is
something we can look at later.
Vegard
PS: Thanks for telling me about how change_page_attr() was wrong in
kmemcheck v2. A lot of things were simply wrong in v2, but hopefully
they are better now :-)
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