[Crash-utility] [BUG] [compressed kdump / SADUMP] makedumpfile header truncation error

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