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 <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent d58831e4
......@@ -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)
if (!memcmp(from+7, "exactmap", 8)) {
/* If we are doing a crash dump, we
* still need to know the real mem
* size before original memory map is
* reset.
saved_max_pfn = max_pfn;
from += 8+7;
e820.nr_map = 0;
userdef = 1;
......@@ -22,6 +22,10 @@ extern unsigned long min_low_pfn;
extern unsigned long max_pfn;
extern unsigned long saved_max_pfn;
* node_bootmem_map is a map pointer - the bits represent all physical
* memory pages (including holes) on the node.
......@@ -33,6 +33,14 @@ EXPORT_SYMBOL(max_pfn); /* This is exported so
* dma_get_required_mask(), which uses
* it, can be an inline function */
* 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;
/* 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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