linux-kernel - Re: [PATCH] random: add rng-seed= command line option

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Date:   Thu, 13 Feb 2020 20:24:54 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>,
        Mark Salyzyn <salyzyn@...roid.com>,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Richard Henderson <richard.henderson@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH] random: add rng-seed= command line option

Hi,

On Fri, 7 Feb 2020 19:53:26 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 7 Feb 2020 19:49:22 -0500
> "Theodore Y. Ts'o" <tytso@....edu> wrote:
> 
> 
> > My preference would be to pass in the random seed *not* on the
> > command-line at all, but as a separate parameter which is passed to
> > the bootloader, just as we pass in the device-tree, the initrd and the
> > command-line as separate things.  The problem is that how we pass in
> > extra boot parameters is architecture specific, and how we might do it
> > for x86 is different than for arm64.  So yeah, it's a bit more
> > inconvenient to do things that way; but I think it's also much
> > cleaner.
> 
> Hmm, if the boot loader could add on to the bootconfig that Masami just
> added, then it could add some "random" seed for each boot! The
> bootconfig is just an appended file at the end of the initrd.

Yeah, it is easy to add bootconfig support to a bootloader. It can add
a entropy number as "rng.seed=XXX" text after initrd image with size
and checksum. That is architecutre independent way to pass such hidden
parameter.
(hidden key must be filtered out when printing out the /proc/bootconfig,
but that is very easy too, just need a strncmp)

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>