llvm dev - Mar 2017 - Linking android with lld: aarch64 target

It would be great if anyone can share your thoughts about the cause and
possibly fix of the error below ?

I would like to know why it is caused and how it can be fixed (if possible)
?

The error message is:

~/llvm/build/install_android/linux-x86/clang-3688880/bin/ld.lld: error:
external/boringssl/linux-aarch64/crypto/sha/sha1-armv8.S:1202: can't create
dynamic relocation R_AARCH64_PREL64 against symbol 'OPENSSL_armcap_P'
defined in out/target/product/hikey/obj/STATIC_LIBRARIES/libcrypto_
intermediates/libcrypto.a(sha1-armv8.o)
clang-5.0: error: linker command failed with exit code 1 (use -v to see
invocation)

cheers,
-- Min
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Hello Min,

This error message occurs when the linker would have to create a
dynamic relocation in a read-only part of the program, which isn't
usually allowed when making a position independent shared-library or
position independent executable. In practice this usually means that
one or more of the objects hasn't been compiled to be position
independent -fPIC.

It is difficult to tell much more without knowing the compiler and
linker options. The R_AARCH64_PREL64 relocation is a relative
relocation, this can require a dynamic relocation if the symbol it
refers to is preemptible (i.e another definition of the symbol could
potentially override it at load-time).

Given that the file sha1-armv8.S is an assembler file, and I assume
that the link with the same inputs works on ld.bfd and ld.gold, I can
only think that it will either be lld is selecting a different object,
or ld.bfd and ld.gold are resolving the R_AARCH64_PREL64 relocation in
this case and lld is not.

Peter

On 23 March 2017 at 04:29, Minseong Kim via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> It would be great if anyone can share your thoughts about the cause and
> possibly fix of the error below ?
>
> I would like to know why it is caused and how it can be fixed (if possible)
> ?
>
> The error message is:
>
> ~/llvm/build/install_android/linux-x86/clang-3688880/bin/ld.lld: error:
> external/boringssl/linux-aarch64/crypto/sha/sha1-armv8.S:1202: can't
create
> dynamic relocation R_AARCH64_PREL64 against symbol
'OPENSSL_armcap_P'
> defined in
>
out/target/product/hikey/obj/STATIC_LIBRARIES/libcrypto_intermediates/libcrypto.a(sha1-armv8.o)
> clang-5.0: error: linker command failed with exit code 1 (use -v to see
> invocation)
>
> cheers,
> -- Min
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

On 23 March 2017 at 21:35, Peter Smith <peter.smith at linaro.org> wrote:
> Hello Min,
>
> This error message occurs when the linker would have to create a
> dynamic relocation in a read-only part of the program, which isn't
> usually allowed when making a position independent shared-library or
> position independent executable. In practice this usually means that
> one or more of the objects hasn't been compiled to be position
> independent -fPIC.
>
OK~ I will check the objects to be linked, if they are compiled (with -fPIC
or not).

It is difficult to tell much more without knowing the compiler
and
> linker options. The R_AARCH64_PREL64 relocation is a relative
> relocation, this can require a dynamic relocation if the symbol it
> refers to is preemptible (i.e another definition of the symbol could
> potentially override it at load-time).
>
> Given that the file sha1-armv8.S is an assembler file, and I assume
> that the link with the same inputs works on ld.bfd and ld.gold, I can
> only think that it will either be lld is selecting a different object,
> or ld.bfd and ld.gold are resolving the R_AARCH64_PREL64 relocation in
> this case and lld is not.
>
Yes, both ld.bfd and ld.gold works with the same inputs. I will keep
looking for the cause with your suggestions in mind.

Thanks again, Peter.

cheers,
-- Min

> Peter
>
> On 23 March 2017 at 04:29, Minseong Kim via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > It would be great if anyone can share your thoughts about the cause
and
> > possibly fix of the error below ?
> >
> > I would like to know why it is caused and how it can be fixed (if
> possible)
> > ?
> >
> > The error message is:
> >
> > ~/llvm/build/install_android/linux-x86/clang-3688880/bin/ld.lld:
error:
> > external/boringssl/linux-aarch64/crypto/sha/sha1-armv8.S:1202:
can't
> create
> > dynamic relocation R_AARCH64_PREL64 against symbol
'OPENSSL_armcap_P'
> > defined in
> > out/target/product/hikey/obj/STATIC_LIBRARIES/libcrypto_
> intermediates/libcrypto.a(sha1-armv8.o)
> > clang-5.0: error: linker command failed with exit code 1 (use -v to
see
> > invocation)
> >
> > cheers,
> > -- Min
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >
>
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