Hi Bernhard, Bernhard Walle wrote: The kdump compressed format is supported by only the crash utility and makedumpfile command. gdb does not support it. I think that there is not any documentation about the kdump compressed format, then I wrote it. Is it enough ? ---------------------------------------------------------------------------- * The kdump compressed format File offset +------------------------------------------+ 0x0 | main header (struct disk_dump_header) | |------------------------------------------+ block 1 | sub header (struct kdump_sub_header) | |------------------------------------------+ block 2 | 1st-bitmap | |------------------------------------------+ block 2 + X blocks (aligned by block) | 2nd-bitmap | |------------------------------------------+ block 2 + 2 * X blocks (aligned by block) | page header for pfn 0 (struct page_desc) | | page header for pfn 1 (struct page_desc) | | : | | page header for pfn Z (struct page_desc) | |------------------------------------------| (not aligned by block) | page data (pfn 0) | | page data (pfn 1) | | : | | page data (pfn Z) | +------------------------------------------+ * main header The main header of the kdump compressed format is the almost same as the one of diskdump. This header has the following members, and the member signature and header_version are different from diskdump. struct disk_dump_header { char signature[SIG_LEN]; /* = "KDUMP " */ int header_version; /* Dump header version */ struct new_utsname utsname; /* copy of system_utsname */ struct timeval timestamp; /* Time stamp */ unsigned int status; /* Above flags */ int block_size; /* Size of a block in byte */ int sub_hdr_size; /* Size of arch dependent header in blocks */ unsigned int bitmap_blocks; /* Size of Memory bitmap in block */ unsigned int max_mapnr; /* = max_mapnr */ unsigned int total_ram_blocks;/* Number of blocks should be written */ unsigned int device_blocks; /* Number of total blocks in * the dump device */ unsigned int written_blocks; /* Number of written blocks */ unsigned int current_cpu; /* CPU# which handles dump */ int nr_cpus; /* Number of CPUs */ struct task_struct *tasks[0]; }; * sub header The sub header of the kdump compressed format is orignal. This header has the member phys_base and dump_level. The member phys_base is for an x86_64 relocatable kernel, and the member dump_level has '-d' option's value of makedumpfile command. struct kdump_sub_header { unsigned long phys_base; int dump_level; /* header_version 1 and later */ }; * 1st-bitmap The bit of 1st-bitmap presents either a page on memory hole, or not. If a page is on memory hole, the corresponding bit is off. Otherwise, it is on. * 2nd-bitmap The bit of 2nd-bitmap presents either a dumpable page, or not. If a page is on memory hole or excluded by makedumpfile command, the corresponding bit is off. Otherwise, it is on. * page header There are page headers corresponding to dumpable pages. This header presents the corresponding page information (compressed, or not. etc.) typedef struct page_desc { off_t offset; /* the offset of the page data*/ unsigned int size; /* the size of this dump page */ unsigned int flags; /* flags */ unsigned long long page_flags; /* page flags */ } page_desc_t; Thanks Ken'ichi Ohmichi

Hi Bernhard, Bernhard Walle wrote: Thank you for the information :-) The manual page is for its usage, and I feel it is better to describe the implementation on the other file (README or IMPLEMENTATION). Thanks Ken'ichi Ohmichi

Hi Bernhard, Sorry for my late response. Bernhard Walle wrote: I have one question. On the site (http://www.suse.de/~bwalle/kdump/vmcore.5.txt), the copyright of SUSE is written. If the part of kdump-compressed format is written to the README file of makedumpfile, is it the problem ? Thanks Ken'ichi Ohmichi