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Re: Bug#644788: Bug#654116: RFH: screen -- terminal multiplexor with VT100/ANSI terminal emulation

On Tue, Jan 03, 2012 at 04:04:04PM +0100, Axel Beckert wrote:
> Hi,
> Roger Leigh wrote:
> [/tmp mounted noexec]
> > > /run/shm (IIRC formerly /dev/shm) likely would be an
> > > alternative option, too.
> > 
> > No, it would not.  This directory is reserved for the eglibc
> > POSIX SHM/SEM interfaces.
> Thanks for this explanation. It's the first time I read or hear about
> the purpose of this mountpoint although I wondered about its purpose
> for years now. (But never actively tried to find out. :-)

shm_overview(7) has some background.  It's not obvious it's in use
because most users unlink their file as soon as it's created, giving
the false impression it's empty!

> Bastian Blank wrote:
> > On Tue, Jan 03, 2012 at 10:05:46AM +0000, Roger Leigh wrote:
> > > If you really need to use a filesystem mounted noexec, just run
> > > the binary via /lib/ld.so (you'll need to get the real location
> > > from e.g. ldd).  Something like:
> > 
> > The kernel does not allow executable mappings from noexec filesystems,
> > so this does not work.
> > 
> > | $ /lib64/ld-linux-x86-64.so.2 ./ls 
> > | ./ls: error while loading shared libraries: ./ls: failed to map segment from shared object: Operation not permitted
> Thanks for the comment. Cc'ing the relevant bug again, as this is
> crucial information when I work on fixing the bug.
> Roger Leigh wrote:
> > Or query for DT_INTERP directly and run that.
> Never heard of that before. Searching the web just found hits
> indicating it seems part of the ELF header. No idea how to work with
> it, though. Any hints?

objdump would probably be the tool of choice.  But if ld.so won't
run programs on noexec filesystems, it's moot.


  .''`.  Roger Leigh
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