Christoph Rohland wrote:
> > I think in both cases, for MAP_SHARED, it should show a shmfs file
> > name if possible (i.e. if it's mounted).
>
> That's probably true.
>
> > From /proc/pid/maps, it's possible to open the shared mapped file whose
> > name is listed and see what the process sees. But that breaks for
> > /dev/zero as a very special case. Using the shmfs name would remove
> > that special case.
>
> Since they always show up as deleted the current solution is still
> correct in your scenario.
By current solution, you mean the one which shows /dev/zero in
/proc/pid/maps?
A program which opens /proc/pid/maps of some other process, and opens
the shared mapped file named in there, will open /dev/zero. And that's
broken: it doesn't show the correct data. For a MAP_PRIVATE mapping,
you get what you expect. But for a MAP_SHARED mapping, it should work
or the open should fail.
> And they have to show up as deleted since this memory object is only
> accesible to the process and its relatives. FD passing et.al. do not
> help for /dev/zero since mmaping the file again gives you a new
> mapping.
?? I was under the impression that the whole point of MAP_SHARED on
/dev/zero is that you can pass the fd around and multiple mappings
return the same pages.
-- Jamie
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This archive was generated by hypermail 2b29 : Sun Apr 23 2000 - 21:00:20 EST