Emit a warning when -z relro is unsupported

[Carlos O'Donell]

On 8/4/20 4:57 PM, Carlos O'Donell wrote:
> On 7/29/20 12:25 PM, Florian Weimer via Libc-alpha wrote:
>> * Alan Modra via Libc-alpha:
>>
>>> From 3425515f19d47eb2e13180fe031d94a9c13ce39b Mon Sep 17 00:00:00 2001
>>> From: Alan Modra <amodra@gmail.com>
>>> Date: Wed, 29 Jul 2020 16:28:57 +0930
>>> Subject: Don't mix linker error messages into edited scripts
>>>
>>> 	* Makerules (shlib.lds): Discard linker warning output.
>>> 	(format.lds): Likewise.
>>>
>>> diff --git a/Makerules b/Makerules
>>> index 341db86c7e..ef0fe67d9a 100644
>>> --- a/Makerules
>>> +++ b/Makerules
>>> @@ -557,7 +557,7 @@ $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>>>  	$(LINK.o) -shared -Wl,-O1 \
>>>  		  -nostdlib -nostartfiles \
>>>  		  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
>>> -		  -Wl,--verbose 2>&1 | \
>>> +		  -Wl,--verbose 2>/dev/null | \
>>>  	  sed > $@T \
>>>  	      -e '/^=========/,/^=========/!d;/^=========/d' \
>>>  	      $(if $(filter yes,$(have-hash-style)), \
>>> @@ -1073,7 +1073,7 @@ ifneq (unknown,$(output-format))
>>>  else
>>>  	$(LINK.o) -shared $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
>>>  		  $(LDFLAGS.so) $(LDFLAGS-lib.so) \
>>> -		  -x c /dev/null -o $@.so -Wl,--verbose -v 2>&1 \
>>> +		  -x c /dev/null -o $@.so -Wl,--verbose -v 2>/dev/null \
>>>  	| sed -n -f $< > $@.new
>>>  	test -s $@.new
>>>  	rm -f $@.so
>>
>> This change looks reasonable to me.  Thanks for tracking this down.
>>
>> We are in the glibc 2.32, so Carlos as the release manager needs to
>> approve this.
> 
> I'm testing this fix for inclusion today before I cut the branch.
 
Fix looks good. I just pushed for glibc 2.32. Thanks Alan!

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

-- 
Cheers,
Carlos.