Re: [PATCH 0/3] Mips support for PT_GNU_STACK

["Maciej W. Rozycki" <macro at linux-mips dot org>]

On Fri, 5 Jul 2019, Dragan Mladjenovic wrote:

> >>> The form of detection the patch proposes is not yet provided by the
> >>> kernel. Instead, this version of the patch does kernel version check
> >>> at runtime and provides compatible behavior if it cannot detect the
> >>> 4.8 kernel or newer.
> >>
> >> People patch their kernels to lie about the version, so I don't think
> >> this is correct.

 It is their problem then, I don't think it's a valid excuse.  We have 
previous art in this area; cf. commit d5f2798a0ac9 ("MIPS: Set the 
required Linux kernel version to 4.5.0 for 2008 NaN") and I reckon there 
have been more cases like this.

> > Could a possible compromise be to forego the run-time check and instead make
> > the non-exec stack override trigger statically for MIPs when building glibc
> > with 4.8 or later kernel headers? In that case, the potential gap between glibc's
> > expectation and an old kernel masquerading as a newer version is exactly what it
> > would be for the usual minimum kernel version check.
> >
> > We'd lose the ability to build against older kernel headers and work seamlessly
> > with newer kernels. This is not ideal, but it is more important to get a
> > working non-executable stack solution out in user space.
> 
> I'm interested if proposed compromise is acceptable for the community to be done in this release cycle?
> If not what else can we do to move this issue forward?

 Submitting stuff late in the cycle never helps, so I think the best 
compromise might be to target 2.31 instead.  And I think a kernel version 
check is the right approach.

  Maciej