On Fri, Jan 09, 2015 at 09:50:42PM +0000, Al Viro wrote:

On Fri, Jan 09, 2015 at 04:28:52PM -0500, Rich Felker wrote:

quoted

The "magic open-once magic symlink" approach is really the cleanest
solution I can find. In the case where the interpreter does not open
the script, nothing terribly bad happens; the magic symlink just
sticks around until _exit or exec. In the case where the interpreter
opens it more than once, you get a failure, but as far as I know
existing interpreters don't do this, and it's arguably bad design. In
any case it's a caught error.

You know what's cleaner than that?  git revert 27d6ec7ad
It has just been merged; until 3.19 it's fair game for removal.

And yes, I should've NAKed the damn thing loud and clear, rather than
asking questions back then, getting no answers and letting it slip.
Mea culpa.

Back then the procfs-free environments had been pushed as a serious argument
in favour of merging the damn thing.  Now you guys turn around and say that
we not only need procfs mounted, we need a yet-to-be-added kludge in there
to cope with the actual intended uses.

Reverting does not fix the problem. There is no way to make fexecve
work for scripts without kernel support, and the needed kernel support
without fexecve would be even nastier, since handling of /proc/self/fd
magic-symlinks would need to be special-cased. The added fexecveat
syscall supports fully /proc-less operation for non-scripts.

Rich