linux-kernel - Re: [PATCH] crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max

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Message-ID: <20110127104713.GA31360@aepfle.de>
Date:	Thu, 27 Jan 2011 11:47:13 +0100
From:	Olaf Hering <olaf@...fle.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crash_dump: export is_kdump_kernel to modules,
 consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn

On Wed, Jan 26, Andrew Morton wrote:

> On Tue, 25 Jan 2011 17:10:52 +0100
> Olaf Hering <olaf@...fle.de> wrote:

> > --- /dev/null
> > +++ linux-2.6.38.rc/kernel/crash_dump.c
> > @@ -0,0 +1,33 @@
> > +#include <linux/crash_dump.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +
> > +/*
> > + * If we have booted due to a crash, max_pfn will be a very low value. We need
> > + * to know the amount of memory that the previous kernel used.
> > + */
> > +unsigned long saved_max_pfn;
> > +
> > +/*
> > + * stores the physical address of elf header of crash image
> > + *
> > + * Note: elfcorehdr_addr is not just limited to vmcore. It is also used by
> > + * is_kdump_kernel() to determine if we are booting after a panic. Hence put
> > + * it under CONFIG_CRASH_DUMP and not CONFIG_PROC_VMCORE.
> > + */
> > +unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
> > +EXPORT_SYMBOL_GPL(elfcorehdr_addr);
> > +
> > +/*
> > + * elfcorehdr= specifies the location of elf core header stored by the crashed
> > + * kernel. This option will be passed by kexec loader to the capture kernel.
> > + */
> > +static int __init setup_elfcorehdr(char *arg)
> > +{
> > +	char *end;
> > +	if (!arg)
> > +		return -EINVAL;
> > +	elfcorehdr_addr = memparse(arg, &end);
> > +	return end > arg ? 0 : -EINVAL;
> > +}
> > +early_param("elfcorehdr", setup_elfcorehdr);
> 
> Please check that this file is #including everything it needs.  Just
> looking at it I'd expect a build error with CONFIG_KEXEC=n,
> CONFIG_CRASH_DUMP=y due to a missed ELFCORE_ADDR_MAX definition.

I'm not sure what you mean?  ELFCORE_ADDR_MAX is in linux/crash_dump.h
defined unconditionally. I dont see the relation to CONFIG_KEXEC.

Olaf
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