[PATCH 0/3] vmcoreinfo support for dump filtering

Ken'ichi Ohmichi oomichi at mxs.nes.nec.co.jp
Wed Aug 22 08:08:38 EDT 2007

Hi Andrew,

This patch set frees the restriction that makedumpfile users should
install a vmlinux file (including the debugging information) into
each system.

makedumpfile command is the dump filtering feature for kdump.
It creates a small dumpfile by filtering unnecessary pages for the
analysis. To distinguish unnecessary pages, it needs a vmlinux file
including the debugging information. These days, the debugging package
becomes a huge file, and it is hard to install it into each system.

To solve the problem, kdump developers discussed it at lkml and kexec-ml.
As the result, we reached the conclusion that necessary information
for dump filtering (called "vmcoreinfo") should be embedded into the
first kernel file and it should be accessed through /proc/vmcore
during the second kernel.

Dan Aloni created the patch set for the above implementation.

And I updated it for multi architectures and memory models.

[1/3] [linux] Add vmcoreinfo
  The patch is for linux-2.6.22.
  The patch adds the vmcoreinfo data. Its address and size are output
  to /sys/kernel/vmcoreinfo.

[2/3] [kexec-tools] Pass vmcoreinfo's address and size
  The patch is for kexec-tools-testing-20070330.
  kexec command gets the address and size of the vmcoreinfo data from
  /sys/kernel/vmcoreinfo, and passes them to the second kernel through
  ELF header of /proc/vmcore. When the second kernel is booting, the
  kernel gets them from the ELF header and creates vmcoreinfo's PT_NOTE
  segment into /proc/vmcore.

[3/3] [makedumpfile] Extract vmcoreinfo from /proc/vmcore
  The patch is for makedumpfile v1.1.6.
  makedumpfile command extracts the vmcoreinfo data from /proc/vmcore
  and uses it for dump filtering.

- Run the first kernel applied with [PATCH 1/3].
- Preload the second kernel by the kexec-tools applied with [PATCH 2/3].
- Cause panic and switch to the second kernel.
- Get a dumpfile by the makedumpfile applied with [PATCH 3/3]:
  (Ex.) # makedumpfile -cd31 /proc/vmcore dumpfile

Ken'ichi Ohmichi

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