Date: Mon, 28 Oct 2019 12:22:55 -0700 From: Kees Cook <keescook@...omium.org> To: Muni Sekhar <munisekharrms@...il.com> Cc: kernel-hardening@...ts.openwall.com Subject: Re: How to get the crash dump if system hangs? 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
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