From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 3E7593858408; Thu, 11 Nov 2021 15:36:39 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3E7593858408
From: "segher at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libgcc/103004] [12 regression] r12-4416 breaks backtrace on
 PPC64 Big-endian
Date: Thu, 11 Nov 2021 15:36:38 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: libgcc
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: segher at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 12.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-103004-4-huzpVrY9FN@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-103004-4@http.gcc.gnu.org/bugzilla/>
References: <bug-103004-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 11 Nov 2021 15:36:39 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103004

--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Bah, I typoed the PR id:

commit 8d71d3a317236ab4a69f441cf867a43aeb448150
Author: Raphael Moreira Zinsly <rzinsly@linux.ibm.com>
Date:   Thu Nov 11 11:40:10 2021 -0300

    libgcc: Fix backtrace fallback on PowerPC Big-endian

    At the end of the backtrace stream _Unwind_Find_FDE() may not be able
    to find the frame unwind info and will later call the backtrace fallback
    instead of finishing. This occurs when using an old libc on ppc64 due to
    dl_iterate_phdr() not being able to set the fde in the last trace.
    When this occurs the cfa of the trace will be behind of context's cfa.
    Also, libgo<E2><80><99>s probestackmaps() calls the backtrace with a nu=
ll
po
    and can get to the backchain fallback with the same problem, in this ca=
se
    we are only interested in find a stack map, we don't need nor can do a
    backchain.
    _Unwind_ForcedUnwind_Phase2() can hit the same issue as it uses
    uw_frame_state_for(), so we need to treat _URC_NORMAL_STOP.

    libgcc/ChangeLog:
        PR libgcc/103044
        * config/rs6000/linux-unwind.h (ppc_backchain_fallback): Check if i=
t's
        called with a null argument or at the end of the backtrace and retu=
rn.
        * unwind.inc (_Unwind_ForcedUnwind_Phase2): Treat _URC_NORMAL_STOP.=