[lld] r340902 - Always add a .note.GNU-stack section if -r.

[Rui Ueyama via llvm-commits]

On Fri, Aug 31, 2018 at 9:55 PM Joerg Sonnenberger <joerg at bec.de> wrote:

> On Thu, Aug 30, 2018 at 10:07:34AM +0900, Rui Ueyama via llvm-commits
> wrote:
> > On Thu, Aug 30, 2018 at 7:16 AM Joerg Sonnenberger <joerg at bec.de> wrote:
> >
> > > On Wed, Aug 29, 2018 at 07:27:09AM -0000, Rui Ueyama via llvm-commits
> > > wrote:
> > > > Author: ruiu
> > > > Date: Wed Aug 29 00:27:09 2018
> > > > New Revision: 340902
> > > >
> > > > URL: http://llvm.org/viewvc/llvm-project?rev=340902&view=rev
> > > > Log:
> > > > Always add a .note.GNU-stack section if -r.
> > > >
> > > > With this patch, lld creates a .note.GNU_stack and adds that to an
> > > > output file if it is creating a re-linkable object file (i.e. if -r
> > > > is given). If we don't do this, and if you use GNU linkers as a final
> > > > linker, they create an executable whose stack area is executable,
> > > > which is considered pretty bad these days.
> > >
> > > It should only be done if at least one of the input files had the note.
> > >
> >
> > I consider .note.GNU-stack a pointless feature at the moment; it could
> make
> > your program's stack area executable in an obscure way. You should pass
> `-z
> > execstack` to the final link command line if your program really need an
> > executable stack.
>
> I consider the whole note pointless. That's exactly why I am complaining
> about adding this junk when it is not necessary or desirable. Not every
> OS follows the stupid glibc model of making the stack executable unless
> told otherwise.


I wanted to completely ignore .note.GNU-stack and don't add the section
when we create an object file. But unfortunately that causes practical
issues that I was trying to fix with the patch. If you don't add the
section, the linker does an insane thing. That's unfortunate, but in
reality we need to add .note.GNU-stack to every object file at the moment.
Once the logic to make the stack area executable is removed from the GNU
linkers, we could remove this code too.
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