linux-kernel - Re: [PATCH 1/2 v6] kdump: add the vmcoreinfo documentation

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Message-ID: <221183717.69773903.1547497592624.JavaMail.zimbra@redhat.com>
Date:   Mon, 14 Jan 2019 15:26:32 -0500 (EST)
From:   Dave Anderson <anderson@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Kazuhito Hagio <k-hagio@...jp.nec.com>,
        Lianbo Jiang <lijiang@...hat.com>,
        linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        akpm@...ux-foundation.org, bhe@...hat.com, dyoung@...hat.com,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2 v6] kdump: add the vmcoreinfo documentation



----- Original Message -----
> On Mon, Jan 14, 2019 at 03:07:33PM -0500, Dave Anderson wrote:
> > That's what it *does* utilize -- it takes a standalone vmcore dumpfile, and
> > pulls out the OSRELEASE string from it, so that a user can determine what
> > vmlinux file should be used with that vmcore for normal crash analysis.
> 
> And the vmcoreinfo is part of the vmcore, right?

Correct.

> 
> So it can just as well read out the address of init_uts_ns and get the
> kernel version from there.

No.  It needs *both* the vmlinux file and the vmcore file in order to read kernel
virtual memory, so just having a kernel virtual address is insufficient.

So it's a chicken-and-egg situation.  This particular --osrelease option is used
to determine *what* vmlinux file would be required for an actual crash analysis 
session.

Dave