linux-kernel - Re: [patch V3 05/11] x86/mm/cpa: Add debug mechanism

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Message-ID: <20180922103316.GH24124@hirez.programming.kicks-ass.net>
Date:   Sat, 22 Sep 2018 12:33:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Bin Yang <bin.yang@...el.com>,
        Mark Gross <mark.gross@...el.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [patch V3 05/11] x86/mm/cpa: Add debug mechanism

On Fri, Sep 21, 2018 at 09:40:36AM -0700, Dave Hansen wrote:
> On 09/17/2018 07:29 AM, Thomas Gleixner wrote:
> > The whole static protection magic is silently fixing up anything which is
> > handed in. That's just wrong. The offending call sites need to be fixed.
> > 
> > Add a debug mechanism which emits a warning if a requested mapping needs to be
> > fixed up. The DETECT debug mechanism is really not meant to be enabled except
> > for developers, so limit the output hard to the protection fixups.
> ...
> > +enum cpa_warn {
> > +	CPA_PROTECT,
> > +	CPA_DETECT,
> > +};
> > +
> > +static const int cpa_warn_level = CPA_PROTECT;
> 
> Even if this is intended for developers only, should we also add some
> config option here so things like 0day can still get warnings out of this?
> 
> Reviewed-by: Dave Hansen <dave.hansen@...el.com>

OTOH, I really wish there was something like: depends !RANDCONFIG
for some of those things, because I triggered
GCC_PLUGIN_STRUCTLEAK_VERBOSE in a randconfig the other day and thought
everything was busted due to the massive output.