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

From: Kees Cook <keescook@chromium.org>
To: Rob Herring <robh+dt@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>,
	Petr Mladek <pmladek@suse.com>,
	Anton Vorontsov <anton@enomsg.org>,
	Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Benson Leung <bleung@chromium.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	devicetree@vger.kernel.org,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v4 6/6] ramoops: Add max_reason optional field to ramoops DT node
Date: Mon, 18 May 2020 16:04:37 -0700	[thread overview]
Message-ID: <202005181603.C8CBA854@keescook> (raw)
In-Reply-To: <CAL_JsqLVgdUEP74nJOHOBD2abK=3YfCqX9GmL2iXdPNctcRdjw@mail.gmail.com>

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@chromium.org> wrote:
> >
> > From: Pavel Tatashin <pasha.tatashin@soleen.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@soleen.com>
> > Link: https://lore.kernel.org/lkml/20200506211523.15077-6-keescook@chromium.org/
> > Signed-off-by: Kees Cook <keescook@chromium.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