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| author |   Marco Elver <elver@google.com> | 2020-02-14 22:10:35 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2020-03-21 09:44:41 +0100 |
| commit | f5d2313bd3c540be405c4977a63840cd6d0167b5 (patch) | |
| tree | 25a8bfd1f857fc11aab179fb67ac36071e9c1503 | |
| parent | kcsan: Introduce ASSERT_EXCLUSIVE_BITS(var, mask) (diff) | |
| download | linux-dev-f5d2313bd3c540be405c4977a63840cd6d0167b5.tar.xz linux-dev-f5d2313bd3c540be405c4977a63840cd6d0167b5.zip | |
kcsan, trace: Make KCSAN compatible with tracing
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).
Reported-by: Qian Cai <cai@lca.pw>
Tested-by: Qian Cai <cai@lca.pw>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/lib/Makefile | 5 | ||||
| -rw-r--r-- | kernel/kcsan/Makefile | 2 | ||||
| -rw-r--r-- | kernel/trace/Makefile | 3 |
3 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index 432a07705677..6110bce7237b 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 df6b7799e492..d4999b38d1be 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 f9dcd19165fa..6b601d88bf71 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) |