[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: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
index d88ebdf..8d58a05 100644
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -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 @@
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 --git a/include/linux/bootmem.h b/include/linux/bootmem.h
index 500f451..82bd884 100644
--- a/include/linux/bootmem.h
+++ b/include/linux/bootmem.h
@@ -22,6 +22,10 @@
*/
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 --git a/mm/bootmem.c b/mm/bootmem.c
index f82f7ae..45275f1 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -33,6 +33,14 @@
* 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)
{