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Description of problem: The glibc exception unwinder in RHEL7 doesn't understand PAC pointers. Potentially this library can be linked into containers/etc which may be used on RHEL8+ machines . As such this functionality should be back-ported into RHEL7 to avoid future problems.


Actual results:
At the moment its believed that various combinations of OS/glibc and PAC will cause application crashes rather than correctly handling exceptions.

Upstream patches:

https://sourceware.org/ml/libc-alpha/2019-06/msg00499.html

Jeremy, the patch has not been merged upstream. My understanding was that the PAC PLT was abandoned, given that it is possible to get much better hardening using BIND_NOW and full RELRO. Would you please clarify? Thanks.

The bug we were expecting from Arm was a bug against gcc for libgcc to be fixed in rhel-7.6.z to support the overlapping unwinding op with the old sparc unwind opcode.

Lets blame this one on me not reading all the email threads, and close it. I will open another one against the correct component, but I have to track down the right commits.