[Crash-utility] [PATCH][v2] Remove __exception_text_start and __exception_text_end for ARM64

[Bhupesh Sharma]

Hi Prabhakar,

On Mon, Dec 30, 2019 at 9:55 AM Prabhakar Kushwaha
<prabhakar.pkin at gmail.com> wrote:
>
> Dear Bhupesh,
>
> On Tue, Dec 24, 2019 at 9:39 AM Prabhakar Kushwaha
> <prabhakar.pkin at gmail.com> wrote:
> >
> > On Tue, Dec 24, 2019 at 1:09 AM Bhupesh Sharma <bhsharma at redhat.com> wrote:
> > >
> > > On Mon, Dec 23, 2019 at 7:49 PM Prabhakar Kushwaha
> > > <prabhakar.pkin at gmail.com> wrote:
> > > >
> > > > On Mon, Dec 23, 2019 at 7:32 PM Dave Anderson <anderson at redhat.com> wrote:
> > > > >
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > > __exception_text_start and __exception_text_end is used to group functions
> > > > > > and place according to linker script in such a way to achieve
> > > > > > kprobe blacklist. Linux commit b6e43c0e3129 ("arm64: remove __exception
> > > > > > annotations") has removed __exception_text_start and
> > > > > > __exception_text_end and uses NOKPROBE_SYMBOL() for blacklist kprobes.
> > > > > >
> > > > > > So removing references of __exception_text_start and __exception_text_end
> > > > > > for ARM64.
> > > > >
> > > > > NAK for a couple of reasons...
> > > > >
> > > > > First, they cannot be removed for backward-compatibility purposes, and secondly
> > > > > an alternative method is required for arm64_back_trace_cmd() for handling
> > > > > exception frames.
> > > > >
> > > >
> > > > We are getting following error with crash tool with latest kernel.
> > > > crash: cannot resolve "__exception_text_start" error
> > > >
> > > > it is because of Linux commit b6e43c0e3129 which removes
> > > > __exception_text_start and __exception_text_end.
> > > > We need to find alternate way of fixing it.
> > >
> > > I cannot seem to remember reproducing this issue with crash with
> > > latest kernel on my arm64 boards.
> > > Can you be more specific on the exact kernel version and the crash
> > > command you used, just to be sure we are able to reproduce the same?
> > >
> >
> > We are seeing this issue on Thuder X platform (arm64).
> >
> > Please find details of commit id.
> > A) crash tool: https://github.com/crash-utility/crash.git
> > commit:  af7f78dc501b8acf7fee3f924f69e93513d0a74b (Fix for the "log -a" option.)
> >
> > B) Linux:  git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > commit:  46cf053efec6a3a5f343fead837777efe8252a46 (Linux 5.5-rc3)
> >
> > C) Kexec: https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
> > commit: bd077966e2b9041c24df5b689e67670f02be7b0d (kexec-tools: Fix
> > conversion overflow when compiling on 32-bit platforms)
> >
> >
> > Logs
> > root at ubuntu$ ./crash /proc/vmcore /usr/src/tovards/linux/vmlinux
> >
> > crash 7.2.7++
> > Copyright (C) 2002-2019  Red Hat, Inc.
> > Copyright (C) 2004, 2005, 2006, 2010  IBM Corporation
> > Copyright (C) 1999-2006  Hewlett-Packard Co
> > Copyright (C) 2005, 2006, 2011, 2012  Fujitsu Limited
> > Copyright (C) 2006, 2007  VA Linux Systems Japan K.K.
> > Copyright (C) 2005, 2011  NEC Corporation
> > Copyright (C) 1999, 2002, 2007  Silicon Graphics, Inc.
> > Copyright (C) 1999, 2000, 2001, 2002  Mission Critical Linux, Inc.
> > This program is free software, covered by the GNU General Public License,
> > and you are welcome to change it and/or distribute copies of it under
> > certain conditions.  Enter "help copying" to see the conditions.
> > This program has absolutely no warranty.  Enter "help warranty" for details.
> >
> > vmcoreinfo : vabits_actual: 48
> > GNU gdb (GDB) 7.6
> > Copyright (C) 2013 Free Software Foundation, Inc.
> > License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> > and "show warranty" for details.
> > This GDB was configured as "aarch64-unknown-linux-gnu".
> > For bug reporting instructions, please see:
> > <http://www.gnu.org/software/gdb/bugs/>...
> >
> > crash: cannot resolve "__exception_text_start"
> >
>
> i hope you got sometime to reproduce this issue.
> It can also be seen on Linux 5.5-rc4 tag
> (fd6988496e79a6a4bdb514a4655d2920209eb85d).
>
> crash-util  commit 5e975dd8c817ea6aea35e1e15b83c378aee9c136 (HEAD ->
> master, origin/master, origin/HEAD)

I was able to reproduce the issue with latest Linus's tree. I am
working on a patch (as per Dave's suggestion) to fix backward
compatibility as well as 'arm64_back_trace_cmd()' (bt command support)
and will post it out soon (I am hoping to post out a version after the
new year break).

Thanks  and a Happy New Year,
Bhupesh