linux-kernel - Re: [PATCH 1/1] pstore/ram: Ensure stable pmsg address with per-CPU ftrace buffers

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Date:   Tue, 11 Oct 2022 15:22:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Paramjit Oberoi <pso@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
        Dmitry Torokhov <dtor@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH 1/1] pstore/ram: Ensure stable pmsg address with per-CPU
 ftrace buffers

On Tue, Oct 11, 2022 at 01:44:54PM -0700, Paramjit Oberoi wrote:
> > > The only downside is it would break some code that works today because
> it
> > > ran in contexts where the pmsg address was stable (no per-cpu ftrace
> > > buffers, or power-of-two CPUs).
> >
> > I don't follow? And actually, I wonder about the original patch now --
> > nothing should care about the actual addresses. Everything should be
> > coming out of the pstore filesystem.
> 
> We are running VMs with the pstore RAM mapped to a file, and using some
> tools outside the VM to read/manipulate the pstore after VM shutdown.

Ah-ha! Interesting. Well, I think it will be more stable this way even
for that. :)

-- 
Kees Cook