Bug 2483120

Description of problem:

libunwind-1.6.2-1.el9.aarch64 segfaults during stack unwinding on aarch64.
This is triggered by tcmalloc (gperftools) which calls GetStackTrace via
libunwind during allocator initialization.

The crash happens during shared library loading (before main()), making
affected binaries completely unusable on arm64. The bug is non-deterministic
in that it depends on allocation patterns — some builds trigger it, others
don't. It is 100% reproducible once triggered.

EPEL10 already ships libunwind 1.8.0 which does not have this bug.
Fedora 42+ ships 1.8.1+. Only epel9 is stuck on the broken 1.6.2.

Impact:

The Ceph project relies on EPEL9 for libunwind. This bug appears and
disappears across Ceph releases as a side effect of unrelated code changes
(any change in allocation patterns during startup can shift the tcmalloc
sampling point). Affected versions include v18.2.4, v20.2.1; other versions
like v19.2.3 and v20.2.0 happen to avoid it by luck. This was discussed
over a year ago in the Ceph community with the conclusion that EPEL9 needs
to be updated:

- https://tracker.ceph.com/issues/67213#note-27 (Ken Dreyer from Red Hat
  confirmed the EPEL9 package needs to be updated)
- https://tracker.ceph.com/issues/76967 (latest occurrence in v20.2.1)
- https://github.com/rook/rook/issues/14502 (Rook/Kubernetes users affected)

Reproducer:

$ podman run --rm quay.io/ceph/ceph:v20 /usr/bin/rbd-mirror
Segmentation fault (core dumped)

Confirmed version:

# rpm -q libunwind
libunwind-1.6.2-1.el9.aarch64

Stack trace (from coredumpctl):

#0  0x0000ffffbd1fb624 n/a (libunwind.so.8.0.1 + 0x3624)
#1  0x0000ffffbd200ee8 n/a (libunwind.so.8.0.1 + 0x8ee8)
#2  0x0000ffffbd200ee8 n/a (libunwind.so.8.0.1 + 0x8ee8)
#3  0x0000ffffbe76c994 n/a (libtcmalloc.so.4.5.9 + 0x2e994)
#4  0x0000ffffbe771ce0 n/a (libtcmalloc.so.4.5.9 + 0x33ce0)
#5  0x0000ffffbe765498 n/a (libtcmalloc.so.4.5.9 + 0x27498)
...
#19 0x0000ffffbecb5be4 n/a (ld-linux-aarch64.so.1 + 0x5be4)
#20 0x0000ffffbecb5cec n/a (ld-linux-aarch64.so.1 + 0x5cec)
#21 0x0000ffffbecc8248 n/a (ld-linux-aarch64.so.1 + 0x18248)

Fix:

The issue was fixed upstream in libunwind v1.7.0 and further hardened
in v1.8.0:

v1.7.0 (full diff_: https://github.com/libunwind/libunwind/compare/v1.6.2...v1.7.0):
- Fix undefined behavior issues in aarch64
  https://github.com/libunwind/libunwind/pull/414
- fix incorrect store in AArch64 getcontext
  https://github.com/libunwind/libunwind/pull/353

v1.8.0 (https://github.com/libunwind/libunwind/releases/tag/v1.8.0):
- aarch64: unw_step() validates address before calling dwarf_get
  https://github.com/libunwind/libunwind/pull/494
- Improve unw_step fallback method on Aarch64
  https://github.com/libunwind/libunwind/pull/571
- Further improvements to unw_step fallback method on AArch64
  https://github.com/libunwind/libunwind/pull/638

EPEL10 already ships 1.8.0. Fedora 42+ ships 1.8.1+. Please update
the epel9 branch to match.