[Bug target/94514] New: aarch64: unwinding across mixed pac-ret and non-pac-ret frames is broken

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94514

            Bug ID: 94514
           Summary: aarch64: unwinding across mixed pac-ret and
                    non-pac-ret frames is broken
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

libgcc unwinder on aarch64 fails to keep track of pauth state and may try to
authenticate return addresses that were not signed causing a runtime crash.

example c++ code that segfaults in the unwinder on a pauth enabled system:

__attribute__((noinline, target("branch-protection=pac-ret")))
static void do_throw (void)
{
  throw 42;
  __builtin_abort ();
}

__attribute__((noinline, target("branch-protection=none")))
static void no_pac_ret (void)
{
  do_throw ();
  __builtin_abort ();
}

int main ()
{
  try {
    no_pac_ret ();
  } catch (...) {
    return 0;
  }
  __builtin_abort ();
}