x86-64 prelink support for TLS dialect gnu2

[Steven Newbury]

On 06/11/2018, Steven Newbury <steven.newbury@googlemail.com> wrote:

> From the reverted ARM prelink patch it's clear the magic is in the
> section guarded
> by RESOLVE_CONFLICT_FIND_MAP.  The x86_64 code already handles several
> different cases of R_X86_64_TLSDESC in that switch so I still don't
> understand how it falls through to _dl_reloc_bad_type rather than just
> ignoring the prelink suppliied address.  Most of the ARM patch
> consists of asserts presumably because the code wasn't fully trusted.
>
Okay, I've applied the attached patch inserting the code removed from
the ARM dl-machine.h into the x86_64 code handling R_X86_64_TLSDESC.
I still get the same error:

error while loading shared libraries: unexpected reloc type 0x24

Which can only be coming from _dl_reloc_bad_type() after it's fallen
through the switch in elf_machine_rela() or the if-else block in
elf_machine_lazy_rel(), both of which have should not fall through
since R_X86_64_TLSDESC is reloc type 0x24 and it is, or should be
handled!
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