[PATCH] makedumpfile: Add description of incomplete dump file

[Atsushi Kumagai]

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.

>+    |  sec_hdr    |         |  sec_hdr    |
>+    |-------------+         |-------------+
>+    |  elf note   |         |  elf note   |
>+    |-------------+         |-------------+
>+    |  segment(1) |         |  segment(1) |
>+    |          :  |         |          :  |
>+    |  segment(N) |         |  segment(N) |  The segment(N) is incomplete.
>+    |          :  |         +-------------+  The segments after N don't exist.
>+    |  segment(Z) |
>+    +-------------+
>+
>+    The incomplete flag is set into e_flags of elf_header by
>+                              e_flags |= DUMP_ELF_INCOMPLETE
>+    DUMP_ELF_INCOMPLETE : 0x1
>+
>+    The PT_LOAD and segment are written in pairs. When writting segment(N)

s/writting/writing/


Thanks,
Atsushi Kumagai

>+    , if ENOSPACE error happens, the PT_LOAD after N won't be written
>+    either.
>+
>+    If there is no segment dumped into the DUMPFILE, the DUMPFILE can't be
>+    analysed by crash.
>--
>1.7.1
>
>
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