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[PATCH] kdump: Retrieve saved max pfn

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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@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Vivek Goyal 2005-06-25 14:58:18 -07:00 • committed by Linus Torvalds
parent d58831e416
commit 92aa63a5a1
3 changed files with 24 additions and 0 deletions
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12
arch/i386/kernel/setup.c
View file

@ -59,6 +59,9 @@
#include "setup_arch_pre.h" #include "setup_arch_pre.h"
#include <bios_ebda.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 /* 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* immediately after the boot time page tables. It contains a *physical*
address, and must not be in the .bss segment! */ 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) if (to != command_line)
to--; to--;
if (!memcmp(from+7, "exactmap", 8)) { 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; from += 8+7;
e820.nr_map = 0; e820.nr_map = 0;
userdef = 1; userdef = 1;

4
include/linux/bootmem.h
View file

@ -22,6 +22,10 @@ extern unsigned long min_low_pfn;
*/ */
extern unsigned long max_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 * node_bootmem_map is a map pointer - the bits represent all physical
* memory pages (including holes) on the node. * memory pages (including holes) on the node.

8
mm/bootmem.c
View file

@ -33,6 +33,14 @@ EXPORT_SYMBOL(max_pfn); /* This is exported so
* dma_get_required_mask(), which uses * dma_get_required_mask(), which uses
* it, can be an inline function */ * 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 */ /* return the number of _pages_ that will be allocated for the boot bitmap */
unsigned long __init bootmem_bootmap_pages (unsigned long pages) unsigned long __init bootmem_bootmap_pages (unsigned long pages)
{ {