From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Fri, 22 Jan 2016 12:52:11 +0000 Subject: [PATCH v2] kernel: add kcov code coverage In-Reply-To: References: <1452689318-107172-1-git-send-email-dvyukov@google.com> <20160118141352.GM21067@leverpostej> <20160122115503.GA10370@leverpostej> Message-ID: <20160122125210.GA10802@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Jan 22, 2016 at 01:15:27PM +0100, Dmitry Vyukov wrote: > On Fri, Jan 22, 2016 at 12:55 PM, Mark Rutland wrote: > > On Mon, Jan 18, 2016 at 09:09:43PM +0100, Dmitry Vyukov wrote: > >> On Mon, Jan 18, 2016 at 8:44 PM, Dmitry Vyukov wrote: > >> > Regarding KASLR and dynamically loaded modules. I've looked at my > >> > use-case and concluded > >> > that most of the time I can work with "non-stable" PCs within a single > >> > VM. Whenever I need to > >> > store PCs persistently or send to another machine, I think I can > >> > "canonicalize" PCs using > >> > /proc/modules and /proc/kallsyms to something like (module hash, > >> > module offset). So kernel does > >> > not need to do this during coverage collection. > >> > >> On second though, maybe it's better to just always export unsigned long PCs... > >> Need to measure how much memory coverage information consumes, > >> and how much slower it is with uint64 PCs. Maybe I can live with large PCs, > >> or maybe I can make syzkaller require !KASLR and compress PCs in user-space... > >> Need to think about this more. > > > > I can imagine we might keep the expanded module range even in the > > absence of full KASLR, though I don't know how realistic that thought > > is. > > The last version of the patch just exposes PCs as unsigned longs > without any compression. So it should not be a problem (at least for > kernel, now it's user responsibility to make sense out of the PCs). Ah, ok. Sorry for the noise! Mark.