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Tue, 23 Jul 2024 00:56:51 -0700 (PDT) MIME-Version: 1.0 References: <20240722223726.194658-1-andrey.konovalov@linux.dev> In-Reply-To: <20240722223726.194658-1-andrey.konovalov@linux.dev> From: Dmitry Vyukov Date: Tue, 23 Jul 2024 09:56:39 +0200 Message-ID: Subject: Re: [PATCH] kcov: don't instrument lib/find_bit.c To: andrey.konovalov@linux.dev Cc: Andrew Morton , Andrey Konovalov , Aleksandr Nogikh , Marco Elver , Alexander Potapenko , kasan-dev@googlegroups.com, linux-mm@kvack.org, Yury Norov , Rasmus Villemoes , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 027FC40020 X-Stat-Signature: 4xzepiewraare8u97kgdjmsdx4fx4f7h X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1721721413-495191 X-HE-Meta: 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 JnHPNV2i FGgNoJL1tEuFYuqjG5lx/qy0CQCDK9TuV+KQ7Je0Dg+wzbPnoErTQ7kWdnVTnrGgZr0hMJ/wRpP701EnCG/35A11eRGDNd10nMYy0hp8deHra+c8tSReArUnVy9VFDAOfXGC8fCQeDm/VOxtxhR2LRTAi7SJdPTwaRXhVsBLzOT7wYMpi9GcfUtQFOOuhK9qOVwwkdWUIz+eRUizwQGmXazPSowO5rvVvGKNdy+aaELVPTjMjCYpqbTlSvCp71/xGXnPcCs9bz3tCpWXkEC6D6JTzsQrcdtIf9yNnB0BbJCDBA8KRU2uh//XqZSG36nuMarOOi3U3NOA3W4f1jAtkBmVT0BnUIoSaJY7dVflLIBf1/Yka4MAO5w5jeC1OYhQSL6ilveneMlXgtphj8WV3hGYdwC2hPmBW0nBPWyqAQIYvsUS7NGFh/MDglIEDdWYa6KTl X-Bogosity: Ham, tests=bogofilter, spamicity=0.000095, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 23 Jul 2024 at 00:37, wrote: > > From: Andrey Konovalov > > This file produces large amounts of flaky coverage not useful for the > KCOV's intended use case (guiding the fuzzing process). > > Signed-off-by: Andrey Konovalov Reviewed-by: Dmitry Vyukov > --- > > I noticed this while running one of the syzkaller's programs. > > In one run of the program, the number of KCOV entries amounts to ~300k, > with the top ones: > > 117285 /home/user/src/lib/find_bit.c:137 (discriminator 10) > 116752 /home/user/src/lib/find_bit.c:137 (discriminator 3) > 2455 /home/user/src/lib/vsprintf.c:2559 > 2033 /home/user/src/fs/kernfs/dir.c:317 > 1662 /home/user/src/fs/kernfs/kernfs-internal.h:72 > ... > > In another run (that triggers exactly the same behavior in the kernel), > the amount of entries drops to ~110k: > > 7141 /home/user/src/lib/find_bit.c:137 (discriminator 10) > 7110 /home/user/src/lib/find_bit.c:137 (discriminator 3) > 2455 /home/user/src/lib/vsprintf.c:2559 > 2033 /home/user/src/fs/kernfs/dir.c:317 > 1662 /home/user/src/fs/kernfs/kernfs-internal.h:72 > ... > > With this patch applied, the amount of KCOV entries for the same program > remains somewhat stable at ~100k. > --- > lib/Makefile | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/lib/Makefile b/lib/Makefile > index 322bb127b4dc..0fde1c360f32 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -14,6 +14,7 @@ KCOV_INSTRUMENT_list_debug.o := n > KCOV_INSTRUMENT_debugobjects.o := n > KCOV_INSTRUMENT_dynamic_debug.o := n > KCOV_INSTRUMENT_fault-inject.o := n > +KCOV_INSTRUMENT_find_bit.o := n > > # string.o implements standard library functions like memset/memcpy etc. > # Use -ffreestanding to ensure that the compiler does not try to "optimize" > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20240722223726.194658-1-andrey.konovalov%40linux.dev.