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

> Hi Prabhakar, > > On Mon, Dec 30, 2019 at 9:55 AM Prabhakar Kushwaha > <prabhakar.pkin(a)gmail.com&gt; wrote: >> >> Dear Bhupesh, >> >> On Tue, Dec 24, 2019 at 9:39 AM Prabhakar Kushwaha >> <prabhakar.pkin(a)gmail.com&gt; wrote: >> > >> > On Tue, Dec 24, 2019 at 1:09 AM Bhupesh Sharma <bhsharma(a)redhat.com&gt; >> wrote: >> > > >> > > On Mon, Dec 23, 2019 at 7:49 PM Prabhakar Kushwaha >> > > <prabhakar.pkin(a)gmail.com&gt; wrote: >> > > > >> > > > On Mon, Dec 23, 2019 at 7:32 PM Dave Anderson >> <anderson(a)redhat.com&gt; 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@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 > Thanks Bhupesh, I'm also out until next week. And yeah, for 5.5 and later kernels it looks like arm64_in_exception_text() will have to check the incoming address's symbol name against the set of exception handler symbol names. The older kernels can still utilize the handy text range between __exception_text_start/__exception_text_end. Kind of a pain, but I don't know what the alternative would be. Dave