From: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Subject: kcov: don't instrument with UBSAN Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug in KCOV, it may cause infinite recursion via printk and other common functions. We already don't instrument KCOV with KASAN/KCSAN for this reason, don't instrument it with UBSAN as well. As a side effect this also resolves the following gcc warning: conflicting types for built-in function '__sanitizer_cov_trace_switch'; expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch] It's only reported when kcov.c is compiled with any of the sanitizers enabled. Size of the arguments is correct, it's just that gcc uses 'long' on 64-bit arches and 'long long' on 32-bit arches, while kernel type is always 'long long'. Link: https://lkml.kernel.org/r/20201209100152.2492072-1-dvyukov@xxxxxxxxxx Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Suggested-by: Marco Elver <elver@xxxxxxxxxx> Acked-by: Marco Elver <elver@xxxxxxxxxx> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/Makefile | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/Makefile~kcov-dont-instrument-with-ubsan +++ a/kernel/Makefile @@ -34,8 +34,11 @@ KCOV_INSTRUMENT_extable.o := n KCOV_INSTRUMENT_stacktrace.o := n # Don't self-instrument. KCOV_INSTRUMENT_kcov.o := n +# If sanitizers detect any issues in kcov, it may lead to recursion +# via printk, etc. KASAN_SANITIZE_kcov.o := n KCSAN_SANITIZE_kcov.o := n +UBSAN_SANITIZE_kcov.o := n CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector obj-y += sched/ _
