PR28827 - [2.38 Regression] ld hits assertion building LLVM 9 on powerpc64le-linux-gnu

[H.J. Lu]

On Fri, Feb 4, 2022 at 3:06 AM Alan Modra <amodra@gmail.com> wrote:
>
> Hi Nick, HJ,
> I've spent most of today debugging a build of libclang-cpp.so.9 using
> the binutils 2.38 release branch.  The problem occurs after only a few
> iterations of stub sizing, so all the patches I already committed for
> potential bugs when we hit 20 iteration don't so anything as far as
> actually linking the real object files.
>
> The problem is caused by the new relro code introducing a gap at the
> end of the relro segment.  On powerpc64 that means between the .got
> and .plt section.  That gap changes when .eh_frame shrinks after
> consolidating CIEs and garbage collecting unused FDEs, which happens
> after the stub sizing passes are run from ldemul_after_allocation.
> Unfortunately, if the .got/.plt gap increases, plt call stubs may need
> to be larger to access addresses in the PLT from the toc pointer reg
> and thus not fit in space allocated for them.

I ran into similar issues when I was implementing DT_RELR on x86.
I added size_relative_relocs and finish_relative_relocs hooks to
resolve them.

> Please revert the relro patches on the branch.  I'm now certain that
> PR28827 is directly caused by them.

I submit a patch to remove the 1-page gap only for x86:

https://sourceware.org/pipermail/binutils/2022-February/119625.html

-- 
H.J.