Re: [PATCH] arm64: ptdump: Allow dumping user page tables

[Vincent Whitchurch]

On Tue, Oct 19, 2021 at 02:09:32PM +0200, Will Deacon wrote:
> On Fri, Oct 01, 2021 at 04:56:03PM +0200, Vincent Whitchurch wrote:
> > Add a user_page_tables debugfs file (similar to kernel_page_tables) to
> > dump out the userspace page tables for the current process.  This
> > provides details which are not available via pagemap (such as the memory
> > type) and is useful when, for example, debugging ->mmap()
> > implementations.
> > 
> > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
> > ---
> >  arch/arm64/mm/ptdump.c | 15 ++++++++++++++-
> >  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> How does this serialise with things like task exit?

A task can only read its own page tables using this file, and the mm
lock is held during the walk in ptdump_walk_pgd().  Isn't that
sufficient?