[Bug libc/29651] glibc can't handle IRELATIVE in .rel.plt only on ARM32 and PPC

["adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29651

Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed:

           What    |Removed                     |Added
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                 CC|                            |adhemerval.zanella at linaro dot o
                   |                            |rg

--- Comment #1 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
It was already reported on binutils [1] and on lld [2]. The current behavior
for ld on arm is to put IRELATIVE on .rel.dyn but I am not sure why exactly
(Peter hinted it is a "legacy of ARM having a single .got section", and I am
not sure if ld still have this limitation yet).

So 'fixing' it won't gain us anything with current supported static linkers. 
It might improve support on arm ifunc itself (for instance to be able to call
R_ARM_JUMP_SLOT functions, since ifunc will be reordered last), but what ifunc
is able to do is not properly documented and has a lot of pitafalls that
calling external functions (from current TU) is always 'tricky'.

And even if we change it, a static-linker that only emits IRELATIVE on .rel.plt
will need to prevent to run on older glibc (as we did for DT_RELR with a extra
symbol).

So the question is whether you need this changed.  Do you need it for your mold
linker?

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=19891
[2] https://reviews.llvm.org/D26029
[3] https://sourceware.org/glibc/wiki/GNU_IFUNC

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