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SubjectRe: [PATCH v9 00/21] Generic page walk and ptdump
On Mon, Jul 22, 2019 at 04:41:49PM +0100, Steven Price wrote:
> This is a slight reworking and extension of my previous patch set
> (Convert x86 & arm64 to use generic page walk), but I've continued the
> version numbering as most of the changes are the same. In particular
> this series ends with a generic PTDUMP implemention for arm64 and x86.
>
> Many architectures current have a debugfs file for dumping the kernel
> page tables. Currently each architecture has to implement custom
> functions for this because the details of walking the page tables used
> by the kernel are different between architectures.
>
> This series extends the capabilities of walk_page_range() so that it can
> deal with the page tables of the kernel (which have no VMAs and can
> contain larger huge pages than exist for user space). A generic PTDUMP
> implementation is the implemented making use of the new functionality of
> walk_page_range() and finally arm64 and x86 are switch to using it,
> removing the custom table walkers.
>
> To enable a generic page table walker to walk the unusual mappings of
> the kernel we need to implement a set of functions which let us know
> when the walker has reached the leaf entry. After a suggestion from Will
> Deacon I've chosen the name p?d_leaf() as this (hopefully) describes
> the purpose (and is a new name so has no historic baggage). Some
> architectures have p?d_large macros but this is easily confused with
> "large pages".
>
> Mostly this is a clean up and there should be very little functional
> change. The exceptions are:
>
> * x86 PTDUMP debugfs output no longer display pages which aren't
> present (patch 14).
>
> * arm64 has the ability to efficiently process KASAN pages (which
> previously only x86 implemented). This means that the combination of
> KASAN and DEBUG_WX is now useable.

Are there any visible changes to the arm64 output?

Could you dump a before/after example somewhere?

Thanks,
Mark.

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