Re: [UNIKRAFT PATCH v3 2/7] build: Link libgcc at the end of the link options list

[Sharan Santhanam <sharan.santhanam@xxxxxxxxx>]

Hey Justin,

Thank you for the update. The patch seems fine.

Thanks & regards
Sharan


Reviewed-by: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>

On 4/9/20 3:36 AM, Justin He wrote:
> Hi Sharan
> For your concern about linking libgcc in Unikraft, here is the reply from our 
> license expert:
>
> > > We have a license question, could BSD licensed project link a GPL licensed 
> > > binary?
> > > *Unikraft* is a BSD licensed project. To support floating-point feature, it 
> > > needs to link libgcc
> > > which is a binary licensed as GPLv3. Will it haves impact on the BSD license in 
> > > Unikraft?
> > The GCC runtime library exception seems to permit the scenario you described.  
> > I believe
> > the license for libgcc includes that exception, and the use-case you described 
> > below appears
> > to otherwise qualify.  You can read the GNU FAQ on this issue HERE  to confirm,
> So seems we can freely linking libgcc without any license issues.
>
> --
> Cheers,
> Justin (Jia He)
>
>
> > -----Original Message-----
> > From: Minios-devel <minios-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf
> > Of Justin He
> > Sent: Tuesday, April 7, 2020 10:27 AM
> > To: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>; minios-
> > devel@xxxxxxxxxxxxxxxxxxxx; Simon Kuenzer <simon.kuenzer@xxxxxxxxx>;
> > Felipe Huici <felipe.huici@xxxxxxxxx>
> > Cc: Kaly Xin <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> > Subject: Re: [Minios-devel] [UNIKRAFT PATCH v3 2/7] build: Link libgcc at the
> > end of the link options list
> >
> > Hi Sharan, thanks for the review
> > For your concern about link gpl binary with bsd project, I will contact our
> > license experts.
> > Will update it asap.
> >
> > --
> > Cheers,
> > Justin (Jia He)
> >
> >
> >
> > > -----Original Message-----
> > > From: Sharan Santhanam <sharan.santhanam@xxxxxxxxx>
> > > Sent: Monday, April 6, 2020 5:34 PM
> > > To: Justin He <Justin.He@xxxxxxx>; minios-devel@xxxxxxxxxxxxxxxxxxxx;
> > > Simon Kuenzer <simon.kuenzer@xxxxxxxxx>; Felipe Huici
> > > <felipe.huici@xxxxxxxxx>
> > > Cc: Kaly Xin <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> > > Subject: Re: [UNIKRAFT PATCH v3 2/7] build: Link libgcc at the end of the
> > link
> > > options list
> > >
> > > Hello Justin,
> > >
> > > Please find the comment inline.
> > >
> > > Thanks & Regards
> > >
> > > Sharan
> > >
> > > On 4/2/20 6:18 AM, Jia He wrote:
> > > > To use newlib on arm64 plat kvm, libgcc should be linked at the end of
> > > > the options list, otherwise it will be ignored due to -stdlib.
> > > >
> > > > Without this patch, there will be a linking error on arm kvm plat:
> > > > syslog.c:(.text+0x7d5cc): undefined reference to `__floatsitf'
> > > > syslog.c:(.text+0x7d5cc): relocation truncated to fit: R_AARCH64_CALL26
> > > against undefined symbol `__floatsitf'
> > > > /root/hj/UK/unikraft_upstream/apps/helloworld/build/helloworld_kvm-
> > > arm64.o: In function `__ieee754_hypotl':
> > > > syslog.c:(.text+0x99434): undefined reference to `__multf3'
> > > > syslog.c:(.text+0x99434): relocation truncated to fit: R_AARCH64_CALL26
> > > against undefined symbol `__multf3'
> > > > syslog.c:(.text+0x99444): undefined reference to `__multf3'
> > > > syslog.c:(.text+0x99444): additional relocation overflows omitted from
> > the
> > > output
> > > > syslog.c:(.text+0x99450): undefined reference to `__addtf3'
> > > > /root/hj/UK/unikraft_upstream/apps/helloworld/build/helloworld_kvm-
> > > arm64.o: In function `sqrtl':
> > > > syslog.c:(.text+0xb12c0): undefined reference to `__trunctfdf2'
> > > > syslog.c:(.text+0xb12c8): undefined reference to `__extenddftf2'
> > > >
> > > > Above undefined symbols are at libgcc.a
> > > >
> > > > Signed-off-by: Jia He <justin.he@xxxxxxx>
> > > > ---
> > > >    plat/kvm/Linker.uk | 2 ++
> > > >    1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/plat/kvm/Linker.uk b/plat/kvm/Linker.uk
> > > > index 5e42193..65a5f8e 100644
> > > > --- a/plat/kvm/Linker.uk
> > > > +++ b/plat/kvm/Linker.uk
> > > > @@ -2,6 +2,7 @@ ifeq (x86_64,$(CONFIG_UK_ARCH))
> > > >    KVM_LDFLAGS-y += -Wl,-m,elf_x86_64
> > > >    else ifeq (arm64,$(CONFIG_UK_ARCH))
> > > >    KVM_LDFLAGS-y         += -Wl,-m,aarch64elf
> > > > +KVM_LINK_LIBGCC_FLAG   := -lgcc
> > > >    endif
> > > >
> > > >
> > > > @@ -26,6 +27,7 @@ $(KVM_DEBUG_IMAGE): $(KVM_ALIBS)
> > $(KVM_ALIBS-y)
> > > $(KVM_OLIBS) $(KVM_OLIBS-y) \
> > > >                         -Wl$(comma)--start-group \
> > > >                         $(KVM_ALIBS) $(KVM_ALIBS-y) \
> > > >                         $(UK_ALIBS) $(UK_ALIBS-y) \
> > > > +                       $(KVM_LINK_LIBGCC_FLAG) \
> > > I think it is fine if we could directly include the libgcc.a into our
> > > statically built binary as this come GPL v3. Do you know if this has an
> > > impact on the BSD license?
> > > >                         -Wl$(comma)--end-group \
> > > >                         -o $(KVM_IMAGE).ld.o)
> > > >         $(call build_cmd,OBJCOPY,,$(KVM_IMAGE).o,\
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