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

[Justin He <Justin.He@xxxxxxx>]

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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