lkml.org 
[lkml]   [2015]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: Regression: Requiring CAP_SYS_ADMIN for /proc/<pid>/pagemap causes application-level breakage
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


\
 
 \ /
  Last update: 2015-04-24 18:01    [W:0.101 / U:0.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site