From 0ebba7141eadc4804ec5b4bb5106331b0c3abf4c Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 14 Nov 2019 19:02:58 +0100 Subject: [PATCH] build, kcsan: Add KCSAN build exceptions This blacklists several compilation units from KCSAN. See the respective inline comments for the reasoning. Signed-off-by: Marco Elver Acked-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- drivers/firmware/efi/libstub/Makefile | 2 ++ kernel/Makefile | 5 +++++ kernel/sched/Makefile | 6 ++++++ mm/Makefile | 8 ++++++++ 4 files changed, 21 insertions(+) diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index ee0661ddb25b..5d0a645c0de8 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -31,7 +31,9 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__DISABLE_EXPORTS GCOV_PROFILE := n +# Sanitizer runtimes are unavailable and cannot be linked here. KASAN_SANITIZE := n +KCSAN_SANITIZE := n UBSAN_SANITIZE := n OBJECT_FILES_NON_STANDARD := y diff --git a/kernel/Makefile b/kernel/Makefile index 74ab46e2ebd1..cc53f7c25446 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -23,6 +23,9 @@ endif # Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip() # in coverage traces. KCOV_INSTRUMENT_softirq.o := n +# Avoid KCSAN instrumentation in softirq ("No shared variables, all the data +# are CPU local" => assume no data races), to reduce overhead in interrupts. +KCSAN_SANITIZE_softirq.o = n # These are called from save_stack_trace() on slub debug path, # and produce insane amounts of uninteresting coverage. KCOV_INSTRUMENT_module.o := n @@ -30,6 +33,7 @@ KCOV_INSTRUMENT_extable.o := n # Don't self-instrument. KCOV_INSTRUMENT_kcov.o := n KASAN_SANITIZE_kcov.o := n +KCSAN_SANITIZE_kcov.o := n CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) # cond_syscall is currently not LTO compatible @@ -118,6 +122,7 @@ obj-$(CONFIG_RSEQ) += rseq.o obj-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak.o KASAN_SANITIZE_stackleak.o := n +KCSAN_SANITIZE_stackleak.o := n KCOV_INSTRUMENT_stackleak.o := n $(obj)/configs.o: $(obj)/config_data.gz diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 21fb5a5662b5..e9307a9c54e7 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -7,6 +7,12 @@ endif # that is not a function of syscall inputs. E.g. involuntary context switches. KCOV_INSTRUMENT := n +# There are numerous races here, however, most of them due to plain accesses. +# This would make it even harder for syzbot to find reproducers, because these +# bugs trigger without specific input. Disable by default, but should re-enable +# eventually. +KCSAN_SANITIZE := n + ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y) # According to Alan Modra , the -fno-omit-frame-pointer is # needed for x86 only. Why this used to be enabled for all architectures is beyond diff --git a/mm/Makefile b/mm/Makefile index d996846697ef..56c1964bb3a1 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -7,6 +7,14 @@ KASAN_SANITIZE_slab_common.o := n KASAN_SANITIZE_slab.o := n KASAN_SANITIZE_slub.o := n +# These produce frequent data race reports: most of them are due to races on +# the same word but accesses to different bits of that word. Re-enable KCSAN +# for these when we have more consensus on what to do about them. +KCSAN_SANITIZE_slab_common.o := n +KCSAN_SANITIZE_slab.o := n +KCSAN_SANITIZE_slub.o := n +KCSAN_SANITIZE_page_alloc.o := n + # These files are disabled because they produce non-interesting and/or # flaky coverage that is not a function of syscall inputs. E.g. slab is out of # free pages, or a task is migrated between nodes.