Re: Should we combine PT_GNU_STACK from DSO?

["H. J. Lu" <hjl at lucon dot org>]

On Fri, Apr 16, 2004 at 05:23:22PM +0200, Jakub Jelinek wrote:
> On Fri, Apr 16, 2004 at 09:50:16AM -0700, H. J. Lu wrote:
> > Currently, we have
> > 
> > [hjl@gnu-psc stack-2]$ make
> > gcc -g   -c -o foo.o foo.c
> > gcc -fPIC -shared -o libbar.so bar.c -Wl,-z,execstack
> > readelf -l libbar.so | grep STACK | grep RWE
> >   STACK          0x000000 0x00000000 0x00000000 0x00000 0x00000 RWE 0x4
> > gcc -o foo foo.o libbar.so -Wl,-rpath,.
> > ./foo
> > Hello
> > readelf -l foo | grep STACK
> >   STACK          0x000000 0x00000000 0x00000000 0x00000 0x00000 RW  0x4
> > readelf -l foo | grep STACK | grep RWE
> > make: *** [all] Error 1
> > 
> > That is we don't combine PT_GNU_STACK from DSO. This executable may
> > fail to run on kernel with non-executable stack. But we can also argue
> > that the DSO used at run-time may not need an executable stack. Any
> > comments?
> 
> We should not.
> The fact that at linktime some shared library needs executable stack
> doesn't mean the one used at runtime will need it as well.
> The dynamic linker handles this at runtime.

I was told that the kernel I was using had a bug which didn't allow
ld.so to change stack permission. So there is no need to change the
kernel.

But ld.so may not do the right thing. I will report it later.


H.J.