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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id l25sm3762879qkk.115.2020.02.14.11.35.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Feb 2020 11:35:58 -0800 (PST) Message-ID: <1581708956.7365.75.camel@lca.pw> Subject: Re: [PATCH] kcsan, trace: Make KCSAN compatible with tracing From: Qian Cai To: Marco Elver Cc: paulmck@kernel.org, andreyknvl@google.com, glider@google.com, dvyukov@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mingo@redhat.com Date: Fri, 14 Feb 2020 14:35:56 -0500 In-Reply-To: <20200214190500.126066-1-elver@google.com> References: <20200214190500.126066-1-elver@google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2020-02-14 at 20:05 +0100, Marco Elver wrote: > Previously the system would lock up if ftrace was enabled together with > KCSAN. This is due to recursion on reporting if the tracer code is > instrumented with KCSAN. > > To avoid this for all types of tracing, disable KCSAN instrumentation > for all of kernel/trace. I remembered that KCSAN + ftrace was working last week, but I probably had a bad memory. Anyway, this patch works fine. Feel free to add, Tested-by: Qian Cai > > Signed-off-by: Marco Elver > Reported-by: Qian Cai > Cc: Paul E. McKenney > Cc: Steven Rostedt > --- > kernel/kcsan/Makefile | 2 ++ > kernel/trace/Makefile | 3 +++ > 2 files changed, 5 insertions(+) > > diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile > index df6b7799e4927..d4999b38d1be5 100644 > --- a/kernel/kcsan/Makefile > +++ b/kernel/kcsan/Makefile > @@ -4,6 +4,8 @@ KCOV_INSTRUMENT := n > UBSAN_SANITIZE := n > > CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_debugfs.o = $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE) > > CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \ > $(call cc-option,-fno-stack-protector,) > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > index f9dcd19165fa2..6b601d88bf71e 100644 > --- a/kernel/trace/Makefile > +++ b/kernel/trace/Makefile > @@ -6,6 +6,9 @@ ifdef CONFIG_FUNCTION_TRACER > ORIG_CFLAGS := $(KBUILD_CFLAGS) > KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS)) > > +# Avoid recursion due to instrumentation. > +KCSAN_SANITIZE := n > + > ifdef CONFIG_FTRACE_SELFTEST > # selftest needs instrumentation > CFLAGS_trace_selftest_dynamic.o = $(CC_FLAGS_FTRACE)