On 09/17/2013 03:45 AM, Dave Anderson wrote:
Recent testing on very large memory systems dictates that an
update is required for the compressed kdump header generated
by makedumpfile.
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;
...
The 32-bit field has also been carried forward into the SADUMP header
as well, which has this in "sadump_mod.h":
struct sadump_header {
...
uint32_t max_mapnr; /* = max_mapnr */
...
And when these header structures change, the crash utility will need
to be changed accordingly.
Preferably for backwards-compatibility, a new header_version can be
created, with the new expanded field located in the kdump_sub_header
so that the original base structure can remain as-is. But I leave that
up to the maintainers.
Thanks,
Dave
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For the persistent data structures, we should use more precision
declaration int32_t, int64_t, uint64_t instead of ambiguous int, long
int, long long int.
For example, we can change structure disk_dump_header as below:
struct disk_dump_header {
char signature[SIG_LEN]; /* = "KDUMP " */
int32_t header_version; /* Dump header version */
struct new_utsname utsname; /* copy of
system_utsname */
struct timeval timestamp; /* Time stamp */
uint32_t status; /* Above flags */
int32_t block_size; /* Size of a block in
byte */
int32_t sub_hdr_size; /* Size of arch dependent
header in blocks */
uint32_t bitmap_blocks; /* Size of Memory bitmap in
block */
uint64_t max_mapnr; /* = max_mapnr */
uint32_t total_ram_blocks;/* Number of blocks
should be
written */
uint32_t device_blocks; /* Number of total
blocks in
* the dump device */
uint32_t written_blocks; /* Number of written
blocks */
uint32_t current_cpu; /* CPU# which handles
dump */
int32_t nr_cpus; /* Number of CPUs */
struct task_struct *tasks[0];
};
--
Thanks,
Jingbai Ma
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