linux-kernel - Re: [PATCH 1/3] jump_label: Warn on failed jump

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Message-ID: <20180215223558.poirr2e6wxs2jhzb@treble>
Date:   Thu, 15 Feb 2018 16:35:58 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Jason Baron <jbaron@...mai.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>, Juergen Gross <jgross@...e.com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 1/3] jump_label: Warn on failed jump_label patch

On Wed, Feb 14, 2018 at 03:17:07PM -0600, Josh Poimboeuf wrote:
> On Wed, Feb 14, 2018 at 12:40:34PM -0500, Steven Rostedt wrote:
> > On Wed, 14 Feb 2018 11:34:07 -0600
> > Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > 
> > 
> > > And in patch 1 the warning conditions need to be tweaked a bit to
> > > exclude the __init case.
> > > 
> > 
> > Hmm, I wonder if we could simply remove the references from the jump
> > label table when init is freed.
> 
> Interesting idea.  The static key's entries (i.e. tracepoint sites) are
> in a static array.  Maybe we could rewrite the affected arrays when init
> memory is freed.  I'm not sure whether that would be overkill though.  I
> can tinker with it and see how it compares to the current solution.

It turns out that something like this is already done for module init
code.  It doesn't *remove* the entry, but it does disable it by setting
entry->code to zero.  I'll just do the same thing right before initmem
is freed.

-- 
Josh