The dumpfile header has this field, which was inherited from
the old "diskdump" facility:
struct disk_dump_header {
...
unsigned int max_mapnr; /* = max_mapnr */
...
and which, among other things, is used by the crash utility as a
delimiter to determine whether a physical address read request is
legitimate. And obviously the field cannot handle PFN values greater
than 32-bits.
The makedumpfile source code does have its own max_mapnr representation
in its DumpInfo structure in "makedumpfile.h":
struct DumpInfo {
...
unsigned long long max_mapnr; /* number of page descriptor */
...
But in its "diskdump_mod.h" file, it carries forward the old diskdump
header format, which has the 32-bit field:
struct disk_dump_header {
...
unsigned int max_mapnr; /* = max_mapnr */
...
And here in "makedumpfile.c", the inadvertent truncation occurs
when the PFN is greater than 32-bits:
int
write_kdump_header(void)
{
...
dh->max_mapnr = info->max_mapnr;
...
Now upstream has below commit to fix this, back port it:
commit 8e124174b62376b17ac909bc68622ef07bde6840
Author: Jingbai Ma <jingbai.ma@hp.com>
Date: Fri Oct 18 18:53:38 2013 +0900
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: WANG Chao <chaowang@redhat.com>
