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

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Message-ID: <202005130045.EF013D12E@keescook>
Date:   Wed, 13 May 2020 00:47:08 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Pavel Tatashin <pasha.tatashin@...een.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 09:34:49AM +0200, Petr Mladek wrote:
> On Tue 2020-05-12 11:45:54, Kees Cook wrote:
> > Here are the problems I see being solved by this:
> > 
> > - lifting kmsg dump reason filtering out of the individual pstore
> >   backends and making it part of the "infrastructure", so that
> >   there is a central place to set expectations. Right now there
> >   is a mix of explicit and implicit kmsg dump handling:
> > 
> >   - arch/powerpc/kernel/nvram_64.c has a hard-coded list
> 
> It handles restart, halt, poweroff the same way.  I wonder if anyone
> would want to distinguish them.
> 
> >   - drivers/firmware/efi/efi-pstore.c doesn't expect anything but
> >     OOPS and PANIC.
> >   - drivers/mtd/mtdoops.c tries to filter using its own dump_oops
> >     and doesn't expect anything but OOPS and PANIC.
> >   - fs/pstore/ram.c: has a hard-coded list and uses its own
> >     dump_oops.
> >   - drivers/mtd/mtdpstore.c (under development[3]) expected only
> >     OOPS and PANIC and had its own dump_oops.
> 
> The others handle only panic or oops.
> 
> What about splitting the reason into two variables? One for severity
> and other for shutdown behavior. I mean:
> 
>   + 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?

-- 
Kees Cook