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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	kernel-team@fb.com, mingo@kernel.org, elver@google.com,
	andreyknvl@google.com, glider@google.com, dvyukov@google.com,
	cai@lca.pw, boqun.feng@gmail.com
Subject: Re: [PATCH kcsan 26/32] kcsan, trace: Make KCSAN compatible with tracing
Date: Mon, 9 Mar 2020 13:27:14 -0700	[thread overview]
Message-ID: <20200309202714.GT2935@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200309155722.49d6bb93@gandalf.local.home>

On Mon, Mar 09, 2020 at 03:57:22PM -0400, Steven Rostedt wrote:
> On Mon,  9 Mar 2020 12:04:14 -0700
> paulmck@kernel.org wrote:
> 
> > From: Marco Elver <elver@google.com>
> > 
> > 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.
> > 
> > Furthermore, since KCSAN relies on udelay() to introduce delay, we have
> > to disable ftrace for udelay() (currently done for x86) in case KCSAN is
> > used together with lockdep and ftrace. The reason is that it may corrupt
> > lockdep IRQ flags tracing state due to a peculiar case of recursion
> > (details in Makefile comment).
> > 
> > Signed-off-by: Marco Elver <elver@google.com>
> > Reported-by: Qian Cai <cai@lca.pw>
> > Cc: Paul E. McKenney <paulmck@kernel.org>
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> 
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Applied, thank you!

							Thanx, Paul

> -- Steve
> 
> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > Tested-by: Qian Cai <cai@lca.pw>
> > ---
> >  arch/x86/lib/Makefile | 5 +++++
> >  kernel/kcsan/Makefile | 2 ++
> >  kernel/trace/Makefile | 3 +++
> >  3 files changed, 10 insertions(+)
> > 
> > diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> > index 432a077..6110bce7 100644
> > --- a/arch/x86/lib/Makefile
> > +++ b/arch/x86/lib/Makefile
> > @@ -8,6 +8,11 @@ KCOV_INSTRUMENT_delay.o	:= n
> >  
> >  # KCSAN uses udelay for introducing watchpoint delay; avoid recursion.
> >  KCSAN_SANITIZE_delay.o := n
> > +ifdef CONFIG_KCSAN
> > +# In case KCSAN+lockdep+ftrace are enabled, disable ftrace for delay.o to avoid
> > +# lockdep -> [other libs] -> KCSAN -> udelay -> ftrace -> lockdep recursion.
> > +CFLAGS_REMOVE_delay.o = $(CC_FLAGS_FTRACE)
> > +endif
> >  
> >  # Early boot use of cmdline; don't instrument it
> >  ifdef CONFIG_AMD_MEM_ENCRYPT
> > diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
> > index df6b779..d4999b3 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 0e63db6..9072486 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)
> 

  reply	other threads:[~2020-03-09 20:27 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 19:03 [PATCH kcsan 0/32] KCSAN commits for v5.7 Paul E. McKenney
2020-03-09 19:03 ` [PATCH kcsan 01/32] kcsan: Prefer __always_inline for fast-path paulmck
2020-03-09 19:03 ` [PATCH kcsan 02/32] kcsan: Show full access type in report paulmck
2020-03-09 19:03 ` [PATCH kcsan 03/32] kcsan: Rate-limit reporting per data races paulmck
2020-03-09 19:03 ` [PATCH kcsan 04/32] kcsan: Make KCSAN compatible with lockdep paulmck
2020-03-09 19:03 ` [PATCH kcsan 05/32] kcsan: Address missing case with KCSAN_REPORT_VALUE_CHANGE_ONLY paulmck
2020-03-09 19:03 ` [PATCH kcsan 06/32] include/linux: Add instrumented.h infrastructure paulmck
2020-03-09 19:03 ` [PATCH kcsan 07/32] asm-generic, atomic-instrumented: Use generic instrumented.h paulmck
2020-03-09 19:03 ` [PATCH kcsan 08/32] asm-generic, kcsan: Add KCSAN instrumentation for bitops paulmck
2020-03-09 19:03 ` [PATCH kcsan 09/32] iov_iter: Use generic instrumented.h paulmck
2020-03-09 19:03 ` [PATCH kcsan 10/32] copy_to_user, copy_from_user: " paulmck
2020-03-09 19:03 ` [PATCH kcsan 11/32] kcsan: Add docbook header for data_race() paulmck
2020-03-09 19:04 ` [PATCH kcsan 12/32] kcsan: Add option to assume plain aligned writes up to word size are atomic paulmck
2020-03-09 19:04 ` [PATCH kcsan 13/32] kcsan: Clarify Kconfig option KCSAN_IGNORE_ATOMICS paulmck
2020-03-09 19:04 ` [PATCH kcsan 14/32] kcsan: Cleanup of main KCSAN Kconfig option paulmck
2020-03-09 19:04 ` [PATCH kcsan 15/32] kcsan: Fix 0-sized checks paulmck
2020-03-09 19:04 ` [PATCH kcsan 16/32] kcsan: Introduce KCSAN_ACCESS_ASSERT access type paulmck
2020-03-09 19:04 ` [PATCH kcsan 17/32] kcsan: Introduce ASSERT_EXCLUSIVE_* macros paulmck
2020-03-13  8:52   ` Boqun Feng
2020-03-13 16:15     ` Marco Elver
2020-03-14  2:22       ` Boqun Feng
2020-03-17 11:12         ` Marco Elver
2020-03-19  3:23           ` Boqun Feng
2020-03-20 14:49             ` Marco Elver
2020-03-09 19:04 ` [PATCH kcsan 18/32] kcsan: Add test to generate conflicts via debugfs paulmck
2020-03-09 19:04 ` [PATCH kcsan 19/32] kcsan: Expose core configuration parameters as module params paulmck
2020-03-09 19:04 ` [PATCH kcsan 20/32] kcsan: Fix misreporting if concurrent races on same address paulmck
2020-03-09 19:04 ` [PATCH kcsan 21/32] kcsan: Move interfaces that affects checks to kcsan-checks.h paulmck
2020-03-09 19:04 ` [PATCH kcsan 22/32] compiler.h, seqlock.h: Remove unnecessary kcsan.h includes paulmck
2020-03-09 19:04 ` [PATCH kcsan 23/32] kcsan: Introduce kcsan_value_change type paulmck
2020-03-09 19:04 ` [PATCH kcsan 24/32] kcsan: Add kcsan_set_access_mask() support paulmck
2020-03-09 19:04 ` [PATCH kcsan 25/32] kcsan: Introduce ASSERT_EXCLUSIVE_BITS(var, mask) paulmck
2020-03-09 19:04 ` [PATCH kcsan 26/32] kcsan, trace: Make KCSAN compatible with tracing paulmck
2020-03-09 19:57   ` Steven Rostedt
2020-03-09 20:27     ` Paul E. McKenney [this message]
2020-03-09 19:04 ` [PATCH kcsan 27/32] kcsan: Add option to allow watcher interruptions paulmck
2020-03-12 18:03   ` Paul E. McKenney
2020-03-12 18:04     ` Paul E. McKenney
2020-03-13 15:28       ` Marco Elver
2020-03-16 13:56         ` Marco Elver
2020-03-16 15:45           ` Paul E. McKenney
2020-03-16 16:22             ` Marco Elver
2020-03-17 17:13               ` Paul E. McKenney
2020-03-17 17:44                 ` Marco Elver
2020-03-18 17:42           ` Marco Elver
2020-03-09 19:04 ` [PATCH kcsan 28/32] kcsan: Add option for verbose reporting paulmck
2020-03-09 19:04 ` [PATCH kcsan 29/32] kcsan: Add current->state to implicitly atomic accesses paulmck
2020-03-09 19:04 ` [PATCH kcsan 30/32] kcsan: Fix a typo in a comment paulmck
2020-03-09 19:04 ` [PATCH kcsan 31/32] kcsan: Update Documentation/dev-tools/kcsan.rst paulmck
2020-03-09 19:04 ` [PATCH kcsan 32/32] kcsan: Update API documentation in kcsan-checks.h paulmck

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