Commit 92aa63a5 authored by Vivek Goyal's avatar Vivek Goyal Committed by Linus Torvalds
Browse files

[PATCH] kdump: Retrieve saved max pfn 



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: default avatarVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d58831e4

arch/i386/kernel/setup.c

+12 −0
Original line number Diff line number Diff line
@@ -59,6 +59,9 @@ 
#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! */
@@ -736,6 +739,15 @@ static void __init parse_cmdline_early (char ** cmdline_p) 
			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;

include/linux/bootmem.h

+4 −0
Original line number Diff line number Diff line
@@ -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.

mm/bootmem.c

+8 −0
Original line number Diff line number Diff line
@@ -33,6 +33,14 @@ EXPORT_SYMBOL(max_pfn); /* This is exported so 
				 * 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)

{

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