Re: PR28827 testcase

[Alan Modra <amodra@gmail.com>]

On Sat, Feb 05, 2022 at 08:26:55PM -0800, H.J. Lu wrote:
> On Sun, Feb 06, 2022 at 02:47:19PM +1030, Alan Modra via Binutils wrote:
> > On Sat, Feb 05, 2022 at 10:39:50AM +0000, Nick Clifton wrote:
> > > Hi Alan, Hi Fangrui,
> > > 
> > > > This testcase triggers a stub sizing error with the patches applied
> > > > for PR28743 (commit 2f83249c13d8 and c804c6f98d34).
> > > > 
> > > > 	PR 28827
> > > > 	* testsuite/ld-powerpc/pr28827-1.s,
> > > > 	* testsuite/ld-powerpc/pr28827-1.d: New test.
> > > > 	* testsuite/ld-powerpc/powerpc.exp: Run it.
> > > 
> > > Given the importance of the PowerPC target, I am going to hold
> > > off from creating the 2.38 release until this issue is fixed.
> > 
> > Thanks, I appreciate it.
> > 
> > >  I do hope however that it can be resolved soon....
> > 
> > The solution is to revert HJ's two relro patches on the branch.  That
> > will let you immediately make a release.  Despite being raised by
> > Florian, I don't believe PR28743 is an important bug to fix just
> > before a release.  Our relro support has sometimes created a hole for
> > *years*.
> > 
> > Of course, the patches ought to be reverted on mainline too,
> > separately from whatever solution we finally adopt for PR28743.
> > 
> 
> Why make removing the 1-page gap before the PT_GNU_RELRO segment opt-in?
> 
> https://sourceware.org/pipermail/binutils/2022-February/119625.html

I happen to think your changes to lang_size_relro_segment_1 are wrong.
Making them optional doesn't fix that.

The major reason is that I question the premise behind the patch.  Is
it really worth wasting up to maxpagesize-1 in memory at the end of
the relro segment in order to remove a page gap at the beginning of
the relro segment?  That seems a dubious trade-off to me.  If process
memory is an issue then it would be better to increase disk image size
for reduced memory size.

There is also the fact that we now hit the do_reset code path in
lang_size_relro_segment when running multiple ld tests.  I think that
says the current implementation is broken.

-- 
Alan Modra
Australia Development Lab, IBM