binutils as policy checker (was: RFC: Add a linker warning when creating segments with RWX permissions)

[Michael Matz <matz@suse.de>]

Hello,

On Tue, 26 Apr 2022, Nick Clifton via Binutils wrote:

>   Following on from the patch to add warnings when the linker creates an
>   executable stack, here is another proposal for a patch to add a
>   warning when the linker creates a memory resident segment with RWX
>   permissions.

Is binutils really the right place to enforce policies?  I'm 
slightly worried about this direction.

I consider all these kinds of checks, which do have some sense, to be 
implementing a certain set of rules that aren't inherent in the design or 
requirements of binary files intended to hold object code and data, i.e. a 
policy.  And for checking adherence to a policy I would expect a policy 
checker tool to be more appropriate than tools designed for creating such 
object files.  Not in the least because policies can sometimes change 
quite quickly (and arbitrarily) and hence need quickly adjustable tooling 
anyway and (even more so) that policies are different for different 
audiences and so encoding one specific policy into a tool looks wrong.

E.g. here I would expect a post-build checker tool to test for RWX 
segments in generated ELF files, like rpmlint and friends, as the distros 
are using already, of course, because that's what the distro makers 
decided to be a policy, not because the binutils authors decided so (I'm 
aware that there's a large overlap in those two sets of people :) ).


Ciao,
Michael.