Re: [PATCH 018/18] kdb-add-kdump-cmd

On Fri, Jul 11, 2008 at 02:16:45AM -0400, jidong xiao wrote:
> As I understand kexec/kdump code is arch dependent, but from your
> patch there is no arch specific piece of code, please can you explain
> this?
> 
> Thanks
> Jason Xiao

Hi Jason,
Well, kdump has a generic component as well a per-arch
support components, so I guess if one is on an arch where
the per-arch component is not present the the call to
crash_kexec() will (hopefully) NOP.  However, I am not a
user of kdump, and we are (so far) an x86-only shop, so the
behavour of crash_kexec() on other arches is unknown to me.

I've forwarded your letter to the author of the patch,
perhaps he will be able to provide additional illumination.

Regards,
Joe

> On Fri, Jul 11, 2008 at 4:57 AM,  <[email protected]> wrote:
> > Add kdump command to KDB.  This command triggers
> > a dump of the kernel via the kexec/kdump mechanism.
> >
> > Author: Jim Houston <[email protected]>
> > Signed-off-by: Joe Korty <[email protected]>
> >
> > Index: 2.6.26-rc9/kdb/modules/Makefile
> > ===================================================================
> > --- 2.6.26-rc9.orig/kdb/modules/Makefile        2008-07-10 12:14:15.000000000 -0400
> > +++ 2.6.26-rc9/kdb/modules/Makefile     2008-07-10 13:41:59.000000000 -0400
> > @@ -6,7 +6,7 @@
> >  # Copyright (c) 1999-2006 Silicon Graphics, Inc.  All Rights Reserved.
> >  #
> >
> > -obj-$(CONFIG_KDB_MODULES) += kdbm_pg.o kdbm_task.o kdbm_vm.o kdbm_sched.o
> > +obj-$(CONFIG_KDB_MODULES) += kdbm_pg.o kdbm_task.o kdbm_vm.o kdbm_sched.o kdbm_kdump.o
> >  obj-m += kdbm_debugtypes.o
> >  ifdef CONFIG_X86
> >  obj-$(CONFIG_KDB_MODULES) += kdbm_x86.o
> > Index: 2.6.26-rc9/kdb/modules/kdbm_kdump.c
> > ===================================================================
> > --- /dev/null   1970-01-01 00:00:00.000000000 +0000
> > +++ 2.6.26-rc9/kdb/modules/kdbm_kdump.c 2008-07-10 13:40:59.000000000 -0400
> > @@ -0,0 +1,43 @@
> > +/*
> > + * This file is subject to the terms and conditions of the GNU General Public
> > + * License.  See the file "COPYING" in the main directory of this archive
> > + * for more details.
> > + *
> > + * Copyright (c) 2006 Concurrent Computer Corp
> > + */
> > +
> > +#include <linux/kdb.h>
> > +#include <linux/kdbprivate.h>
> > +#include <linux/module.h>
> > +#include <linux/init.h>
> > +#include <linux/irq.h>
> > +#include <linux/sched.h>
> > +#include <linux/kexec.h>
> > +
> > +
> > +MODULE_AUTHOR("Concurrent Computer Corp");
> > +MODULE_DESCRIPTION("interface to request kdump crash dump");
> > +MODULE_LICENSE("GPL");
> > +
> > +static int
> > +kdbm_kdump(int argc, const char **argv)
> > +{
> > +       kdb_printf("Calling crash_kexec\n");
> > +       crash_kexec(get_irq_regs());
> > +       kdb_printf("crash_kexec failed\n");
> > +       return 0;
> > +}
> > +
> > +static int __init kdbm_kdump_init(void)
> > +{
> > +       kdb_register("kdump",  kdbm_kdump, "", "request kdump crash dump", 0);
> > +       return 0;
> > +}
> > +
> > +static void __exit kdbm_kdump_exit(void)
> > +{
> > +       kdb_unregister("kdump");
> > +}
> > +
> > +module_init(kdbm_kdump_init)
> > +module_exit(kdbm_kdump_exit)
> > Index: 2.6.26-rc9/kernel/kexec.c
> > ===================================================================
> > --- 2.6.26-rc9.orig/kernel/kexec.c      2008-07-10 12:12:51.000000000 -0400
> > +++ 2.6.26-rc9/kernel/kexec.c   2008-07-10 13:40:59.000000000 -0400
> > @@ -19,6 +19,7 @@
> >  #include <linux/reboot.h>
> >  #include <linux/ioport.h>
> >  #include <linux/hardirq.h>
> > +#include <linux/module.h>
> >  #include <linux/elf.h>
> >  #include <linux/elfcore.h>
> >  #include <linux/utsrelease.h>
> > @@ -1077,6 +1078,7 @@
> >                BUG_ON(!locked);
> >        }
> >  }
> > +EXPORT_SYMBOL_GPL(crash_kexec);
> >
> >  static u32 *append_elf_note(u32 *buf, char *name, unsigned type, void *data,
> >                            size_t data_len)
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