Re: [PATCH 5/7] configure: Unnest detection of -z,relro and -z,now

[Thomas Huth]

On 18/12/2019 17.58, Richard Henderson wrote:
> On 12/17/19 10:11 PM, Thomas Huth wrote:
>>> +# Detect support for DT_BIND_NOW.
>>> +if compile_prog "" "-Wl,-z,now" ; then
>>> +  LDFLAGS="-Wl,-z,now $LDFLAGS"
>>> +fi
>>> +
>>> +# Detect support for PT_GNU_RELRO.
>>> +if compile_prog "" "-Wl,-z,relro" ; then
>>> +  LDFLAGS="-Wl,-z,relro $LDFLAGS"
>>> +fi
>>
>> Looking at
>> https://mudongliang.github.io/2016/07/11/relro-a-not-so-well-known-memory-corruption-mitigation-technique.html
>> the idea of specifying these two options together was likely to get
>> "Full RELRO" instead of only "Partial RELRO".
> 
> Sure.
> 
>> Thus, does it make sense to have "-Wl,-z,now" without "-Wl,-z,relro" in
>> QEMU? Or should this rather check whether both are possible, then use
>> both, otherwise just try to use "relro" alone?
> 
> Honestly, I expect them both to be supported in any binutils.
> 
> I split the two tests just because they didn't seem to be logically connected.
>  But I had forgotten about, or perhaps never heard, the terms "full" and
> "partial" relro.
> 
> I can put them back together with an appropriate comment it you like.  One 
> less
> thing to run during configure...

Yes, please.

 Thanks,
  Thomas