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From: Kees Cook <keescook@chromium.org>
To: Muni Sekhar <munisekharrms@gmail.com>
Cc: kernel-hardening@lists.openwall.com
Subject: Re: How to get the crash dump if system hangs?
Date: Mon, 28 Oct 2019 12:22:55 -0700	[thread overview]
Message-ID: <201910281220.D2ABC01B@keescook> (raw)
In-Reply-To: <CAHhAz+g6RBPKfUMne6Me_ha3FwUWj6a_pA=dYshyjAtOuu+SfA@mail.gmail.com>

On Fri, Oct 25, 2019 at 07:40:58AM +0530, Muni Sekhar wrote:
> After loading the ramoops module, I see it generates dmesg and console logs.

Excellent!

> I’ve a actual test case where my system gets frozen  so have no
> software control. I executed this test case and as expected my system
> has frozen and recovered it by powering it on(cold boot?) and then
> loaded the ramoops but this time no files present in /sys/fs/pstore.

I wonder if you could use a hardware watchdog driver of some kind to
trigger the soft reboot?

> If you restart a PC in cold(hard) boot, is it possible to see the RAM
> memory(previous boot) still? I really I don’t know how it works.

It depends a lot on your chipset and RAM. It sounds like your system
very quickly wipes its RAM contents on a cold reset.

> So, is there a  way to automatically reboot the Linux system when it
> freezes? I set “kernel.softlockup_panic = 1, kernel.unknown_nmi_panic
> = 1, kernel.softlockup_all_cpu_backtrace = 1, kernel.panic = 1,
> kernel.panic_on_io_nmi = 1, kernel.panic_on_oops = 1,
> kernel.panic_on_stackoverflow = 1, kernel.panic_on_unrecovered_nmi =
> 1”, but it does not helped to reboot when it freezes.

See if Documentation/nmi_watchdog.txt helps?

Good luck!

-- 
Kees Cook

  reply	other threads:[~2019-10-28 19:23 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-25 20:17 How to get the crash dump if system hangs? Muni Sekhar
2019-09-30 23:51 ` Kees Cook
2019-10-03 16:48   ` Muni Sekhar
2019-10-03 21:36     ` Kees Cook
2019-10-10 15:49       ` Muni Sekhar
2019-10-10 16:56         ` Kees Cook
2019-10-10 17:15           ` Muni Sekhar
2019-10-10 18:31             ` Kees Cook
2019-10-11 14:03               ` Muni Sekhar
2019-10-25  2:10                 ` Muni Sekhar
2019-10-28 19:22                   ` Kees Cook [this message]
2019-10-20 19:01 youling257
2019-10-21  8:39 ` Lukas Odzioba
2019-10-21 10:22   ` youling 257
2019-11-02  5:42     ` youling 257
2019-10-20 19:31 youling257

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