lkml.org 
[lkml]   [2020]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH kcsan 26/32] kcsan, trace: Make KCSAN compatible with tracing
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)
>

\
 
 \ /
  Last update: 2020-03-09 21:28    [W:0.060 / U:6.284 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site