linux-kernel - RE: [PATCH 1/2 v2] kdump: add the vmcoreinfo documentation

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Message-ID: <4AE2DC15AC0B8543882A74EA0D43DBEC03564659@BPXM09GP.gisp.nec.co.jp>
Date:   Mon, 10 Dec 2018 21:10:41 +0000
From:   Kazuhito Hagio <k-hagio@...jp.nec.com>
To:     Borislav Petkov <bp@...en8.de>, lijiang <lijiang@...hat.com>
CC:     "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "bhe@...hat.com" <bhe@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "dyoung@...hat.com" <dyoung@...hat.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: RE: [PATCH 1/2 v2] kdump: add the vmcoreinfo documentation

-----Original Message-----
> > makedumpfile doesn't have any switch which dumps VMCOREINFO from kcore
> > for now. (I'm thinking to have makedumpfile dump it as debug message,
> > though.)
> 
> Might be useful as people are looking into using VMCOREINFO when
> debugging a live kernel...

Now makedumpfile in 'devel' branch can print VMCOREINFO in /proc/kcore
as debug message with the following command:

# ./makedumpfile --mem-usage /proc/kcore -D
...
VMCOREINFO   :
  OSRELEASE=4.20.0-0.rc2.git0.1.fc30.x86_64
  PAGESIZE=4096
page_size    : 4096
  SYMBOL(init_uts_ns)=ffffffff84213540
  ...

Also, it seems that recent crash utility in git repo with kernel 4.19
or newer can dump it with 'help -n' command:

# ./crash vmlinux /proc/kcore
...
crash> help -n
...
  Elf64_Nhdr:
      n_namesz: 11 ("VMCOREINFO")
      n_descsz: 1955
        n_type: 0 (unknown)

      OSRELEASE=4.20.0-0.rc2.git0.1.fc30.x86_64
      PAGESIZE=4096
      SYMBOL(init_uts_ns)=ffffffff84213540
      ...

Thanks,
Kazu