Messages in this thread | | | From | Mark Seaborn <> | Date | Fri, 24 Apr 2015 08:26:52 -0700 | Subject | Re: Regression: Requiring CAP_SYS_ADMIN for /proc/<pid>/pagemap causes application-level breakage |
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On 24 April 2015 at 08:01, Mark Williamson <mwilliamson@undo-software.com> wrote: > In our use of /proc/PID/pagemap, we currently make use of the physical > pageframe addresses. We should be able to work with a scrambled > representation of these (Andy Lutomirski suggested this in the > original discussion - https://lkml.org/lkml/2015/3/16/1273) so long as > the scrambling remained consistent during the lifetime of the open > pagemap file. Alternatively, if physical addresses were simply zeroed > (also suggested by Pavel Emelyanov - > https://lkml.org/lkml/2015/3/9/871) we would be able to change our > code to rely only on the soft-dirty flag and thus still work > correctly.
I'm curious, what do you use the physical page addresses for?
Since you pointed to http://undo-software.com, which talks about reversible debugging tools, I can guess you would use the soft-dirty flag to implement copy-on-write snapshotting. I'm guessing you might use physical page addresses for determining when the same page is mapped twice (in the same process or different processes)?
Cheers, Mark
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