> -----Original Message-----
> From: gcc-patches-ow...@gcc.gnu.org [mailto:gcc-patches-
> ow...@gcc.gnu.org] On Behalf Of Nagaraju Mekala
> Sent: Thursday, September 21, 2017 2:56 PM
> To: Joseph Myers <jos...@codesourcery.com>
> Cc: sch...@suse.de; gcc-patches@gcc.gnu.org; l...@redhat.com;
> d...@anglin.bell.net; wil...@tuliptree.org; Michael Eager
> <ea...@eagercon.com>
> Subject: RE: Enable no-exec stacks for more targets using the Linux kernel
>
> [This sender failed our fraud detection checks and may not be who they
> appear to be. Learn about spoofing at http://aka.ms/LearnAboutSpoofing]
>
> > -----Original Message-----
> > From: Joseph Myers [mailto:jos...@codesourcery.com]
> > Sent: Wednesday, September 20, 2017 5:52 PM
> > To: Nagaraju Mekala <nmek...@xilinx.com>
> > Cc: sch...@suse.de; gcc-patches@gcc.gnu.org; l...@redhat.com;
> > d...@anglin.bell.net; wil...@tuliptree.org; Michael Eager
> > <ea...@eagercon.com>
> > Subject: Re: Enable no-exec stacks for more targets using the Linux
> > kernel
> >
> > On Wed, 20 Sep 2017, Nagaraju Mekala wrote:
> >
> > > > I've sent a glibc patch
> > > > <https://sourceware.org/ml/libc-alpha/2017-09/msg00734.html>. I
> > > >think the key questions for architecture experts now are: on each
> > > >of those three architectures, do trampolines ever require
> > > >executable stacks, and, if they do, how does this work at present
> > > >when the kernel defaults to non-executable and my understanding at
> > > ><https://sourceware.org/ml/libc-alpha/2017-09/msg00747.html> would
> > > >be that glibc would only make thread stacks executable on those
> > > >architectures, not the main process stacks, and GCC will never
> > > >generate an explicit marker on those architectures to request an
> > > >executable
> > stack?
> > >
> > > Microblaze is a soft processor with many configuration options. If
> > > we don't use the MMU, there is nothing preventing execution of code
> > > on the stack in the MicroBlaze architecture.
> > > With the MMU, you have the option to make any page, including the
> > > stack pages, executable or not.
> > >
> > > It is recommended to prevent execution on the stack by defining
> > > those pages as non-executable in the MMU. In particular, trampolines
> > > would have to be possible to code without execution on the stack
> >
> > No-MMU configurations are not relevant to a glibc change; the question
> > is how things work for configurations using glibc, with the Linux
> > kernel, with an MMU. In such a configuration, for MicroBlaze: (a) is
> > the stack in fact executable, now; (b) if it is, what makes it so
> > given the kernel default to non- executable (where does my reasoning
> > about what the kernel and glibc do go wrong); (c) if it is not executable,
> > do
> trampolines work anyway?
>
> The MMU configuration doesn't need stack to be executable.
> The glibc patch related to Microblaze looks correct and it should solve the
> issue.
> We will verify the change in a day or two and get back to you.
>
Sorry for the confusion.
We need to apply this GCC patch for Microblaze target and make stack executable.
I have verified the patch and there are no regressions with it.
Thanks,
Nagaraju
>
> > --
> > Joseph S. Myers
> > jos...@codesourcery.com
