Re: Should we combine PT_GNU_STACK from DSO?

[Ian Lance Taylor <ian at wasabisystems dot com>]

"H. J. Lu" <hjl@lucon.org> writes:

> 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?

It seems to me that the dynamic linker has to be responsible for this.
Otherwise we will fail if the shared library is updated and
PT_GNU_STACK changes.  I see no reason for the binutils linker to
handle it.

Note that the scheme falls apart when using dlopen in any case.

Ian