linux-kernel - Re: [PATCH v4 6/6] ramoops: Add max_reason optional field to ramoops DT node

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Message-ID: <202005181603.C8CBA854@keescook>
Date:   Mon, 18 May 2020 16:04:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Pavel Tatashin <pasha.tatashin@...een.com>,
        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>,
        Benson Leung <bleung@...omium.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v4 6/6] ramoops: Add max_reason optional field to ramoops
 DT node

On Mon, May 18, 2020 at 04:45:32PM -0600, Rob Herring wrote:
> On Fri, May 15, 2020 at 12:44 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > From: Pavel Tatashin <pasha.tatashin@...een.com>
> 
> Subject still has 'max_reason'.
> 
> >
> > Currently, it is possible to dump kmsges for panic, or oops.
> > With max_reason it is possible to dump messages for other
> 
> And here.

Ah yeah, this was, I think, describing the internal field name, but I
see it would be less confusing to refer to this by the DT name. I will
adjust it. Thanks!

-Kees

> 
> > kmesg_dump events, for example reboot, halt, shutdown, kexec.
> >
> > Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> > Link: https://lore.kernel.org/lkml/20200506211523.15077-6-keescook@chromium.org/
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> >  .../devicetree/bindings/reserved-memory/ramoops.txt | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/reserved-memory/ramoops.txt b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
> > index 0eba562fe5c6..b7886fea368c 100644
> > --- a/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
> > +++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
> > @@ -30,7 +30,7 @@ Optional properties:
> >  - ecc-size: enables ECC support and specifies ECC buffer size in bytes
> >    (defaults to 0: no ECC)
> >
> > -- record-size: maximum size in bytes of each dump done on oops/panic
> > +- record-size: maximum size in bytes of each kmsg dump.
> >    (defaults to 0: disabled)
> >
> >  - console-size: size in bytes of log buffer reserved for kernel messages
> > @@ -45,7 +45,16 @@ Optional properties:
> >  - unbuffered: if present, use unbuffered mappings to map the reserved region
> >    (defaults to buffered mappings)
> >
> > -- no-dump-oops: if present, only dump panics (defaults to panics and oops)
> > +- max-reason: if present, sets maximum type of kmsg dump reasons to store
> > +  (defaults to 2: log Oopses and Panics). This can be set to INT_MAX to
> > +  store all kmsg dumps. See include/linux/kmsg_dump.h KMSG_DUMP_* for other
> > +  kmsg dump reason values. Setting this to 0 (KMSG_DUMP_UNDEF), means the
> > +  reason filtering will be controlled by the printk.always_kmsg_dump boot
> > +  param: if unset, it will be KMSG_DUMP_OOPS, otherwise KMSG_DUMP_MAX.
> > +
> > +- no-dump-oops: deprecated, use max_reason instead. If present, and
> > +  max_reason is not specified, it is equivalent to max_reason = 1
> 
> And here (3 times).
> 
> > +  (KMSG_DUMP_PANIC).
> >
> >  - flags: if present, pass ramoops behavioral flags (defaults to 0,
> >    see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).
> > --
> > 2.20.1
> >

-- 
Kees Cook