[RFC/PATCH 8/17][Kdump] Retrieve saved max pfn

[Vivek Goyal]

> --- Begin Message ---
> From: "Vivek Goyal" <vgoyal@xxxxxxxxxx>
>
> o This patch retrieves the max_pfn being used by previous kernel and stores
>   it in a safe location (saved_max_pfn) before it is overwritten due to user
>   defined memory map. This pfn is used to make sure that user does not try to
>   read the physical memory beyond saved_max_pfn.
>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
>
>  linux-2.6.12-rc1-mm1-1M-root/arch/i386/kernel/setup.c |   12 ++++++++++++
>  linux-2.6.12-rc1-mm1-1M-root/include/linux/bootmem.h  |    4 ++++
>  linux-2.6.12-rc1-mm1-1M-root/mm/bootmem.c             |    8 ++++++++
>  3 files changed, 24 insertions(+)
>
> diff -puN arch/i386/kernel/setup.c~crashdump-x86-retrieve-max-pfn arch/i386/kernel/setup.c
> --- linux-2.6.12-rc1-mm1-1M/arch/i386/kernel/setup.c~crashdump-x86-retrieve-max-pfn	2005-03-22 15:47:33.000000000 +0530
> +++ linux-2.6.12-rc1-mm1-1M-root/arch/i386/kernel/setup.c	2005-03-22 15:47:33.000000000 +0530
> @@ -57,6 +57,9 @@
>  #include "setup_arch_pre.h"
>  #include <bios_ebda.h>
>  
> +/* Forward Declaration. */
> +void __init find_max_pfn(void);
> +
>  /* This value is set up by the early boot code to point to the value
>     immediately after the boot time page tables.  It contains a *physical*
>     address, and must not be in the .bss segment! */
> @@ -715,6 +718,15 @@ static void __init parse_cmdline_early (
>  			if (to != command_line)
>  				to--;
>  			if (!memcmp(from+7, "exactmap", 8)) {
> +#ifdef CONFIG_CRASH_DUMP
> +				/* If we are doing a crash dump, we
> +				 * still need to know the real mem
> +				 * size before original memory map is
> +				 * reset.
> +				 */
> +				find_max_pfn();
> +				saved_max_pfn = max_pfn;
> +#endif
>  				from += 8+7;
>  				e820.nr_map = 0;
>  				userdef = 1;
> diff -puN include/linux/bootmem.h~crashdump-x86-retrieve-max-pfn include/linux/bootmem.h
> --- linux-2.6.12-rc1-mm1-1M/include/linux/bootmem.h~crashdump-x86-retrieve-max-pfn	2005-03-22 15:47:33.000000000 +0530
> +++ linux-2.6.12-rc1-mm1-1M-root/include/linux/bootmem.h	2005-03-22 15:47:33.000000000 +0530
> @@ -22,6 +22,10 @@ extern unsigned long min_low_pfn;
>   */
>  extern unsigned long max_pfn;
>  
> +#ifdef CONFIG_CRASH_DUMP
> +extern unsigned long saved_max_pfn;
> +#endif
> +
>  /*
>   * node_bootmem_map is a map pointer - the bits represent all physical 
>   * memory pages (including holes) on the node.
> diff -puN mm/bootmem.c~crashdump-x86-retrieve-max-pfn mm/bootmem.c
> --- linux-2.6.12-rc1-mm1-1M/mm/bootmem.c~crashdump-x86-retrieve-max-pfn	2005-03-22 15:47:33.000000000 +0530
> +++ linux-2.6.12-rc1-mm1-1M-root/mm/bootmem.c	2005-03-22 15:47:33.000000000 +0530
> @@ -33,6 +33,14 @@ EXPORT_SYMBOL(max_pfn);		/* This is expo
>  				 * dma_get_required_mask(), which uses
>  				 * it, can be an inline function */
>  
> +#ifdef CONFIG_CRASH_DUMP
> +/*
> + * 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;
> +#endif
> +
>  /* return the number of _pages_ that will be allocated for the boot bitmap */
>  unsigned long __init bootmem_bootmap_pages (unsigned long pages)
>  {
> _
>
> --- End Message ---