get the backup area dynamically

Currently we hard-coded the first 640K area as backup area,
however, this is not correct on some system which has reserved
memory area in the first 640K:

BIOS-e820: 0000000000010000 - 0000000000097000 (usable)
BIOS-e820: 0000000000097000 - 00000000000a0000 (reserved)

on such system we still mark all the first 640K as usable
in capture kernel, this will cause kernel panic.

The solution, pointed by Vivek, is that we can get the backup
area dynamically by reading /proc/iomem.

The reporter has tested this patch and it fixes the problem.

Signed-off-by: WANG Cong <amwang@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

1 files changed, 10 insertions, 3 deletions

diff --git a/purgatory/arch/i386/crashdump_backup.c b/purgatory/arch/i386/crashdump_backup.c
index c6194460..365eb5d8 100644
--- a/purgatory/arch/i386/crashdump_backup.c
+++ b/purgatory/arch/i386/crashdump_backup.c
@@ -20,13 +20,15 @@
 
 #include <stdint.h>
 #include <string.h>
-#include "../../../kexec/arch/i386/crashdump-x86.h"
 
 /* Backup region start gets set after /proc/iomem has been parsed. */
 /* We reuse the same code for x86_64 also so changing backup_start to
    unsigned long */
 unsigned long  backup_start = 0;
 
+unsigned long backup_src_start = 0;
+unsigned long backup_src_size = 0;
+
 /* Backup first 640K of memory to backup region as reserved by kexec.
  * Assuming first 640K has to be present on i386 machines and no address
  * validity checks have to be performed. */
@@ -34,11 +36,16 @@ unsigned long  backup_start = 0;
 void crashdump_backup_memory(void)
 {
 	void *dest, *src;
+	size_t size;
+
+	src = (void *) backup_src_start;
+	size = (size_t) backup_src_size;
 
-	src = (void *) BACKUP_SRC_START;
+	if (!size)
+		return;
 
 	if (backup_start) {
 		dest = (void *)(backup_start);
-		memcpy(dest, src, BACKUP_SRC_SIZE);
+		memcpy(dest, src, size);
 	}
 }