RFR: 8130017: use _FORTIFY_SOURCE in gcc fastdebug builds - was : RE: gcc FORTIFY_SOURCE application security flags

[sgehwolf at redhat.com]

Hi Matthias,

For some background about the -O2 -ffp-contract=off flags for
sharedRuntimeTrig.cpp and sharedRuntimeTrans.cpp see:
https://bugs.openjdk.java.net/browse/JDK-8210425

My understanding is that if there is a per-file override of the
optimization level, the compilation command will end up containing both
-O3 and a later, possible override, via the per-file settings. The -O3
flag originates from it being a release/fastdebug build.

Thanks,
Severin

On Wed, 2019-05-08 at 13:27 +0000, Baesken, Matthias wrote:
> Hello,    I looked a bit  more  into it .
> It seems to me ,  that   when  -ffp-contract=off   is
> available  which is the case with  current gcc versions ,  we want to
> optimize the 2 special files ( sharedRuntimeTrig.cpp /
> sharedRuntimeTrans.cpp ).
>  see the following comments :
> 
> jdk/make/hotspot/lib/JvmOverrideFiles.gmk
> 
> 47# If the FDLIBM_CFLAGS variable is non-empty we know
> 48# that the fdlibm-fork in hotspot can get optimized
> 49# by using -ffp-contract=off on GCC/Clang platforms.
>   ......
> 58  BUILD_LIBJVM_sharedRuntimeTrig.cpp_CXXFLAGS := -DNO_PCH
> $(FDLIBM_CFLAGS) $(LIBJVM_FDLIBM_COPY_OPT_FLAG)
> 59  BUILD_LIBJVM_sharedRuntimeTrans.cpp_CXXFLAGS := -DNO_PCH
> $(FDLIBM_CFLAGS) $(LIBJVM_FDLIBM_COPY_OPT_FLAG)
> 60
> 
> But still, setting both -O3 and -O2  in one compile call looks not
> nice to me .
> 
> In case of  ancient gcc  ***without***  -ffp-contract=off   ,  we
> might still run into issues for these  2 special files  when
> _FORTIFY_SOURCE  is set .
> Don't know if this is  still relevant .
> In case  we want to be on the very safe side , we
> might  need  to  filter out   -D_FORTIFY_SOURCE=2    for these 2
> compilation units .
> 
> 
> Best regards, Matthias
> 
> 
> 
> > Hi David,   thanks for the comment .
> > 
> > Currently  I do not see the issue in our fastdebug  builds .
> > So I think the  opt-flag filtering got changed/removed in the
> > years  after the
> > issues were reported .
> > 
> > 
> > https://bugs.openjdk.java.net/browse/JDK-8047952
> > 
> > mentions special O-level settings  for  sharedRuntimeTrig.cpp and
> > sharedRuntimeTrans.cpp .
> > 
> > But the files  have optimization set in both  fastdebug
> > and  opt  builds  :
> > 
> >  Linux  x86_64  gcc-7 based builds :
> > 
> >    fastdebug build  (with the added  -D_FORTIFY_SOURCE=2  flag) :
> > 
> > -Werror -O3 -D_FORTIFY_SOURCE=2 -DNO_PCH -ffp-contract=off -O2 -
> > D_FORTIFY_SOURCE=2
> > 
> > 
> > Opt build  (without  -D_FORTIFY_SOURCE=... ) :
> > 
> > -O3 -DNO_PCH -ffp-contract=off -O2  ....
> > 
> > 
> > (btw.  the setting  of  both    -O3 AND -O2   looks strange to me ,
> > but that’s
> > unrelated to my change ;  I  noticed that already in OpenJDK 11  ).
> > 
> > 
> > Best regards, Matthias
> > 
> > 
> > 
> > 
> > > Hi Matthias,
> > > 
> > > On 8/05/2019 6:05 pm, Baesken, Matthias wrote:
> > > > Hello, here is  a   webrev,  I used the existing bug
> > > > "JDK-8130017 : use _FORTIFY_SOURCE in gcc fastdebug builds"
> > > > 
> > > > Hope that’s fine .
> > > 
> > > That is fine, but please add a comment to the bug explaining
> > > exactly how
> > > you fixed the issue and how the issues raised in the bug
> > > description
> > > regarding optimisation levels have been addressed.
> > > 
> > > Not a review - I'll leave that to build team. The proof of this
> > > will be
> > > in the building and testing.
> > > 
> > > Thanks,
> > > David
> > > 
> > > > https://bugs.openjdk.java.net/browse/JDK-8130017
> > > > 
> > > > http://cr.openjdk.java.net/~mbaesken/webrevs/8130017.0/
> > > > 
> > > > 
> > > > Our internal OpenJDK Linux   (x86_64, ppc64, ppc64le ,
> > > > s390x)   fastdebug
> > > builds  are fine with the added flag .
> > > >