linux-kernel - Re: [PATCH v6 4/4] vsprintf: Add command line option debug_boot_weak

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Message-ID: <20180530042744.GA14188@eros>
Date:   Wed, 30 May 2018 14:27:44 +1000
From:   "Tobin C. Harding" <me@...in.cc>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Kees Cook <keescook@...omium.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Theodore Ts'o <tytso@....edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 4/4] vsprintf: Add command line option
 debug_boot_weak_hash

On Mon, May 28, 2018 at 10:40:43AM -0700, Randy Dunlap wrote:
> On 05/27/2018 06:46 PM, Tobin C. Harding wrote:
> > Currently printing [hashed] pointers requires enough entropy to be
> > available.  Early in the boot sequence this may not be the case
> > resulting in a dummy string '(____ptrval____)' being printed.  This
> > makes debugging the early boot sequence difficult.  We can relax the
> > requirement to use cryptographically secure hashing during debugging.
> > This enables debugging while keeping development/production kernel
> > behaviour the same.
> > 
> > If new command line option debug_boot_weak_hash is enabled use
> > cryptographically insecure hashing and hash pointer value immediately.
> > 
> > Cc: Anna-Maria Gleixner <anna-maria@...utronix.de>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Randy Dunlap <rdunlap@...radead.org>
> > Signed-off-by: Tobin C. Harding <me@...in.cc>
> > ---
> >  Documentation/admin-guide/kernel-parameters.txt |  9 +++++++++
> >  lib/vsprintf.c                                  | 20 ++++++++++++++++++++
> >  2 files changed, 29 insertions(+)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index f2040d46f095..8a86d895343e 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -753,6 +753,15 @@
> >  
> >  	debug		[KNL] Enable kernel debugging (events log level).
> >  
> 
> Hi,
> This is much more readable than the previous version.  Thanks.

Thanks for following up with this one Randy.

	Tobin