On 11/13/2014 05:01 PM, Atsushi Kumagai wrote: > Hello Zhou, > >> Add description of incomplete elf and kdump-compressed dump file >> in IMPLEMENTATION. > > That's a good idea, thanks Zhou. > I have some comments. > >> Signed-off-by: Qiao Nuohan<qiaonuohan at cn.fujitsu.com> >> Signed-off-by: Zhou Wenjian<zhouwj-fnst at cn.fujitsu.com> >> --- >> IMPLEMENTATION | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 files changed, 76 insertions(+), 0 deletions(-) >> >> diff --git a/IMPLEMENTATION b/IMPLEMENTATION >> index 2f4cfd6..8f8a945 100644 >> --- a/IMPLEMENTATION >> +++ b/IMPLEMENTATION >> @@ -112,3 +112,79 @@ >> unsigned long long page_flags; /* page flags */ >> } page_desc_t; >> >> +* The incomplete DUMPFILE >> + When generating DUMPFILE, if ENOSPACE error happens, the DUMPFILE will be >> + incomplete. >> + >> + - The incomplete kdump-compressed DUMPFILE >> + >> + the complete the incomplete >> + +-----------------------+ +-----------------------+ >> + | main header | | main header | have incomplete flag >> + |-----------------------+ |-----------------------+ >> + | sub header | | sub header | >> + |-----------------------+ |-----------------------+ >> + | 1st-bitmap | | 1st-bitmap | >> + |-----------------------+ |-----------------------+ >> + | 2nd-bitmap | | 2nd-bitmap | >> + |-----------------------+ |-----------------------+ >> + | page header for pfn 0 | | page header for pfn 0 | >> + | page header for pfn 1 | | page header for pfn 1 | >> + | : | | : | >> + | page header for pfn N | | page header for pfn N | The page headers after >> + | : | | | N don't exist. The >> + | page header for pfn Z | | | value of it is zero, >> + |-----------------------| |-----------------------| when try to read it. >> + | page data (pfn 0) | | page data (pfn 0) | >> + | page data (pfn 1) | | page data (pfn 1) | >> + | : | | : | >> + | page data (pfn N) | | page data (pfn N) | >> + | : | +-----------------------+ >> + | page data (pfn Z) | >> + +-----------------------+ >> + >> + The incomplete flag is set into status of disk_dump_header by >> + status |= DUMP_DH_COMPRESSED_INCOMPLETE >> + DUMP_DH_COMPRESSED_INCOMPLETE : 0x8 >> + >> + The page header and page data are written in pairs. When writting page data > > s/writting/writing/ > >> + (pfn N+1), if ENOSPACE error happens, the page headers after N won't be >> + written either. >> + >> + If there is no page data dumped into the DUMPFILE, the DUMPFILE can't be >> + analysed by crash. >> + >> + - The incomplete elf DUMPFILE > > There is no description of the ELF format itself in this documentation > unlike the kdump-compressed format, I would be glad if you could write it. > >> + >> + the complete the incomplete >> + +-------------+ +-------------+ >> + | elf header | | elf header | have incomplete flag >> + |-------------+ |-------------+ >> + | PT_NOTE | | PT_NOTE | >> + | PT_LOAD(1) | | PT_LOAD(1) | >> + | : | | : | >> + | PT_LOAD(N) | | PT_LOAD(N) | The PT_LOAD after N don't exist. >> + | : | | | The value of it is zero, when try >> + | PT_LOAD(Z) | | | to read it. >> + |-------------+ |-------------+ > > The whole program header must exist since reserve_diskspace() > pre-allocates enough space for it, the description above isn't right. > The space exists, but since PT_LOAD and segment are written in pairs, if ENOSPACE happens, the left PT_LOAD won't be generated and won't be written as well. The space reserved is for the PT_LOAD still in buffer. -- Thanks Zhou Wenjian
