Re: [RFC PATCH] aarch64: ld: fix relaxations for ilp32 mode

[Yury Norov <ynorov at caviumnetworks dot com>]

On Tue, Jan 17, 2017 at 12:20:39PM +0000, Jiong Wang wrote:
> On 17/01/17 08:48, Yury Norov wrote:
> >On Mon, Jan 16, 2017 at 10:13:43AM +0000, Jiong Wang wrote:
> >>On 14/01/17 10:48, Yury Norov wrote:
> >>>Hi all,
> >>>
> >>>This patch continues the work of replacing 64-bit registers, offsets etc with
> >>>32-bit ones in elfNN_aarch64_tls_relax(). It doesn't fix any test I have tried,
> >>>but it's generally correct, and I think that it should be applied.
> >>>
> >>>I also added new tests for ilp32 mode, and the problem is that some fail. So I'd
> >>>like to ask for help here.
> >>>Namely, 3 new tests are failed. tls-relax-large-desc-ie-ilp32 and
> >>>tls-relax-large-desc-le-ilp32 fail due to error "cannot represent
> >>>BFD_RELOC_AARCH64_TLSDESC_OFF_G1 relocation in this object file format", and
> >>>test tls-desc-ie-ilp32 fails due to weird "undefined reference to `v2".
> >>>
> >>>If my understanding is correct, this error is because GAS cannot translate
> >>>assembler commands to machine codes properly. If so, it may happen with some real
> >>>program one day.
> >>>
> >>>It may also be my misunderstanding on how gas/ld work.
> >>The "undefined reference to v2" is caused by missing of "-shared" in your linker command.
> >Thank you, it works. My fail.
> >
> >>BFD_RELOC_AARCH64_TLSDESC_OFF_G1 and the several other relocations in the
> >>error message are designed to be used by large code model only, so they are
> >>not expected to be generated under ILP32.
> >Hmm... Frankly, I don't understand how to proceed with that. The
> >simplest way is to drop that couple of tests and resend the patch.
> >
> >But for me there's a problem here. If some asm file will contain the
> >instruction sequence like in those tests, compilation will fail. It
> >may come, say, from C inline asm, or whatsoever...
> >
> >Maybe we should wrap that relocations with "#if ARCH_SIZE == 64 ... #endif"
> >like it has been done for BFD_RELOC_AARCH64_TLSG_MOW_G1 and
> >BFD_RELOC_AARCH64_TLSGD_MOVW_G0_NC?
> 
> That looks correct to me, simply move those existed relocations into the existed ARCH_SIZE == 64 check block.

Simple move into "ARCH_SIZE == 64" block doesn't work. At least, tests still
produce that errors. Now I'm thinking to drop tls-relax-large-desc-ie-ilp32
and tls-relax-large-desc-le-ilp32, and resend the patch, and then get deeper
into the problem. Is the rest of the patch OK with this change?

Yury