Re: [Crash-utility] [PATCH 0/1] Add --kaslr support for s390x
----- Original Message -----
Hello Mikhail, Philipp and Gerald,
For the first time today I'm testing a 5.2.0-0.rc1 kernel that has
been configured with CONFIG_RANDOMIZE_BASE=y, and I have verified
that it runs live using the KERNELOFFSET value from the /proc/kcore
VMCOREINFO as the --kalsr argument.
For live system analysis, it seems that the existing kaslr
code in symbols.c should be able to calculate the offset
by comparing the _stext values from /proc/kallsyms and the
the vmlinux file. But obviously it doesn't, although I
haven't investigate why not.
Also, I can't create a kdump dumpfile, so I can't test that,
so it's not clear whether the initial patchset also requires
the -kaslr argument for vmcores?
Anyway, are you guys planning to post a follow-on patch to make
things work automagically both live and with kdumps?
Thanks,
Dave
Just to follow-up...
The current KASLR-checking code in kaslr_init() looks for an x86-only variable,
so for s390x, this simple patch makes live system work without --kalsr:
--- a/symbols.c
+++ b/symbols.c
@@ -609,6 +609,12 @@ kaslr_init(void)
st->_stext_vmlinux = UNINITIALIZED;
}
+ if (machine_type("S390X") && /* Linux 5.2 */
+ (symbol_value_from_proc_kallsyms("__kaslr_offset") != BADVAL)) {
+ kt->flags2 |= (RELOC_AUTO|KASLR);
+ st->_stext_vmlinux = UNINITIALIZED;
+ }
+
if (QEMU_MEM_DUMP_NO_VMCOREINFO()) {
if (KDUMP_DUMPFILE() && kdump_kaslr_check()) {
kt->flags2 |= KASLR_CHECK;
Proof of the pudding:
# ./crash
crash 7.2.6++
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.
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 "s390x-ibm-linux-gnu"...
WARNING: kernel relocated [1239MB]: patching 65462 gdb minimal_symbol values
KERNEL: /usr/lib/debug/lib/modules/5.2.0-0.rc1.1.elrdy.s390x/vmlinux
DUMPFILE: /proc/kcore
CPUS: 2
DATE: Wed May 22 15:29:37 2019
UPTIME: 04:04:45
LOAD AVERAGE: 0.22, 0.10, 0.08
TASKS: 138
NODENAME: ibm-z-113.rhts.eng.bos.redhat.com
RELEASE: 5.2.0-0.rc1.1.elrdy.s390x
VERSION: #1 SMP Mon May 20 22:23:41 EDT 2019
MACHINE: s390x (unknown Mhz)
MEMORY: 2 GB
PID: 8322
COMMAND: "crash"
TASK: 69739000 [THREAD_INFO: 69739000]
CPU: 1
STATE: TASK_RUNNING (ACTIVE)
crash>
And it appears that kdump vmcores with KERNELOFFSET should just work, no?
Dave