linux-kernel - Re: [PATCH v3 0/6] allow ramoops to collect all kmesg

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Date:   Wed, 13 May 2020 13:15:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     Petr Mladek <pmladek@...e.com>, Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Rob Herring <robh+dt@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        James Morris <jmorris@...ei.org>,
        Sasha Levin <sashal@...nel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 0/6] allow ramoops to collect all kmesg_dump events

On Wed, May 13, 2020 at 10:35:16AM -0400, Pavel Tatashin wrote:
> > >   + reason: panic, oops, emergency, shutdown    (ordered by severity)
> > >   + handling: restart, halt, poweroff
> > >
> > > Or we might just replace KMSG_DUMP_RESTART, KMSG_DUMP_HALT,
> > > KMSG_DUMP_POWEROFF with a single KMSG_DUMP_SHUTDOWN.
> > >
> > > Then the max reason variable would make sense.
> >
> > That would work for me, yeah. Pavel, is that enough granularity for you?
> >
> 
> Yes, I like the second approach: where we combine all shutdown type
> events into a single type.
> max_reason will have 4 levels:
> 
>    KMSG_DUMP_PANIC,
>    KMSG_DUMP_OOPS,
>    KMSG_DUMP_EMERG,
>    KMSG_DUMP_SHUTDOWN,
> 
> If needed it is possible to determine from dmesg logs what kind of
> shutdown was taken, because there is a message logged right before
> every kmsg_dump() for these events:
> 
> 249   if (!cmd)
> 250   pr_emerg("Restarting system\n");
> 251   else
> 252   pr_emerg("Restarting system with command '%s'\n", cmd);
> 253   kmsg_dump(KMSG_DUMP_RESTART);
> 
> 276   pr_emerg("System halted\n");
> 277   kmsg_dump(KMSG_DUMP_HALT);
> 
> 294   pr_emerg("Power down\n");
> 295   kmsg_dump(KMSG_DUMP_POWEROFF);
> 
> Kees, I will submit a new series with these changes soon.

Great; thanks!

-Kees

-- 
Kees Cook