[Bug gas/26141] New: -fvisibility=hidden generates JUMP11 relocations on ARM

[jason at zx2c4 dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26141

            Bug ID: 26141
           Summary: -fvisibility=hidden generates JUMP11 relocations on
                    ARM
           Product: binutils
           Version: 2.33
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: jason at zx2c4 dot com
  Target Milestone: ---

There used to be a problem with binutils where JUMP11 relocations would be
generated for THUMB2 code, prompting the linux kernel to add this interesting
workaround:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/Kconfig?id=5e857ce6eae7ca21b2055cca4885545e29228fe2#n1431

This worked, but was suboptimal, so in time binutils fixed the bug, tracked
here: https://sourceware.org/bugzilla/show_bug.cgi?id=12532

AFAICT, the fix there worked, and the kernel no longer generates JUMP11
relocations in THUMB2 mode and all is well.

However, the fix appears to stop working with -fvisibility=hidden. I imagine
this is so due to some conflicting code where the forced B.W is only generated
for static functions, since non-static ones will be relocated differently, but
then because of -fvisibility=hidden, they get treated like statics, only B is
used instead of the forced B.W, causing this issue to crop up again.

OpenWRT experienced this when including WireGuard on a new board. I fixed it
like this:
https://git.zx2c4.com/wireguard-linux-compat/commit/?id=178cdfffb99f2fd6fb4a5bfd2f9319461d93f53b

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