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

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Message-ID: <202210111302.3179DB77@keescook>
Date:   Tue, 11 Oct 2022 13:04:04 -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 12:59:50PM -0700, Paramjit Oberoi wrote:
> > Hm, interesting point. Since only ftrace is dynamically sized in this
> > fashion, how about just moving the pmsg allocation before ftrace, and
> > adding a comment that for now ftrace should be allocated last?
> 
> That is a good idea, and it would solve the problem.
> 
> 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.

-- 
Kees Cook