> > > <snip>
> > >
> > >>> libselinux only "sorts" in the sense of giving precedence to exact
> > >>> (no regex characters) entries.  The sorting described in the page
> > >>> you referenced is done by libsemanage or by the fc_sort helper
> > >>> program used in the refpolicy build and is not part of Android at
> > >>> all.  That sorting was introduced to help with ambiguities that
> > >>> occur when file_contexts was split into per-module .fc files.
> > >>That's essentially the problem we have in our build. Each module is
> > >>added
> > during the build via sepolicy dirs variable. Perhaps then we should
> > look at adding fc_sort during build?
> > >>Android however
> > >>> only has a single monolithic file_contexts file, and even with the
> > >>> device-specific file_contexts, the assumption is that those
> > >>> entries should always take precedence over the generic ones (as
> > >>> long as they are not identical and conflict).  So order does
> > >>> matter.  Last matching entry wins.
> > >
> > > Does anyone object to adding something like sort_fc to the build to
> > > alleviate
> > this ordering issue?
> > >
> > > Now that we switch to checking the fc files with checkfc, I'm not
> > > aware of any
> > other CTS issues.
> >
> > I guess the question is whether we want to sort the entire
> > file_contexts this way (which could potentially cause an entry from
> > the AOSP general file_contexts to override a device-specific entry) or
> > individually sort the general and device- specific file_contexts and
> > then concatenate the two.  The sorting is heuristic- based, as there
> > is no precise ordering that can be defined among regular expressions.
> 
> IIUC,  If we sort the entire fc entries (general + device), then the 
> heuristics per
> that fedora page would allow "more specific" device entries to override 
> general
> entries.
> 
> However, just sorting the device policy would also be Ok with me, since it 
> would
> solve my issue In the modular style policy build.
> 
> >
> > > BTW in the CTS test, why didn't we just modify checkfc to return
> > > status codes
> > for equal, subset, superset? We have all this "complicated"
> > > stdio checking for exact matching.
> >
> > I followed the example of other tests which were output-based, and
> > also exit status can be misleading, e.g. you have to ensure that you
> > are not misinterpreting a shell exit code (e.g. checkfc could not be
> > found or could not be
> > executed) as the exit code of checkfc itself, and that you cleanly
> > delineate all possible exit statuses of the program.


I'm assuming silence means no one objects to doing this on Android, so now the 
question is
Implementation. Looks as though libsemanage has some fc sorting code for this, 
do we use that
or roll our own python script for this. The other thing, I can't find fc_sort 
or sort_fc, can someone
point to where that source is?


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