Date: Sat, 26 May 2018 14:07:38 -0700 From: Cy Schubert <Cy.Schubert@cschubert.com> To: Gleb Smirnoff <glebius@FreeBSD.org> Cc: Mateusz Guzik <mjguzik@gmail.com>, "Jonathan T. Looney" <jtl@freebsd.org>, Matthew Macy <mmacy@freebsd.org>, John Baldwin <jhb@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r334104 - in head/sys: netinet sys Message-ID: <201805262107.w4QL7d4F041579@slippy.cwsent.com> In-Reply-To: Message from Gleb Smirnoff <glebius@FreeBSD.org> of "Wed, 23 May 2018 21:47:46 -0700." <20180524044746.GX71675@FreeBSD.org>
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In message <20180524044746.GX71675@FreeBSD.org>, Gleb Smirnoff writes: > On Thu, May 24, 2018 at 06:44:20AM +0200, Mateusz Guzik wrote: > M> I fundamentally disagree with this part. > M> > M> If a known value of a given field is needed for assertion purposes, you > M> can add (possibly conditional) code setting this specific value. It > M> probably should not be zero if it can be helped. > M> > M> Conditional zeroing of the *whole* struct depending on invariants will > M> *hide* uninitialized memory read bugs - production kernel will have > M> whatever it happens to find, while *debug* kernel will guarantee to > M> have all the values zeroed. In fact the flag actively combats redzoning. > M> if the resulting allocation is zeroed, poisoning is actively neutered. > M> But only if debug is enabled. > M> > M> That said, I find the change harmful. > > +1 on fundamentally disagree with M_ZERO_INVARIANTS. It makes the > INVARIANTS-enabled kernels to crash _later_ than production kernels, > since instead of uma_junk it places clean zeroes. > > May be changes like that deserve more than a 30 minute time frame for review? +1. I think phab might help. -- Cheers, Cy Schubert <Cy.Schubert@cschubert.com> FreeBSD UNIX: <cy@FreeBSD.org> Web: http://www.FreeBSD.org The need of the many outweighs the greed of the few.
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