Re: [PATCH v5 17/38] kmsan: disable KMSAN instrumentation for certain kernel parts

[Andrey Konovalov <andreyknvl@google.com>]

On Wed, Mar 25, 2020 at 5:13 PM <glider@google.com> wrote:
>
> Instrumenting some files with KMSAN will result in kernel being unable
> to link, boot or crashing at runtime for various reasons (e.g. infinite
> recursion caused by instrumentation hooks calling instrumented code again).
>
> Disable KMSAN in the following places:
>  - arch/x86/boot and arch/x86/realmode/rm, as KMSAN doesn't work for i386;
>  - arch/x86/entry/vdso, which isn't linked with KMSAN runtime;
>  - three files in arch/x86/kernel - boot problems;
>  - arch/x86/mm/cpu_entry_area.c - recursion;
>  - EFI stub - build failures;
>  - kcov, stackdepot, lockdep - recursion.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> To: Alexander Potapenko <glider@google.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Vegard Nossum <vegard.nossum@oracle.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: linux-mm@kvack.org

Reviewed-by: Andrey Konovalov <andreyknvl@google.com>

>
> ---
>
> v4:
>  - fix lockdep support by not instrumenting lockdep.c
>  - unified comments with KCSAN
>
> Change-Id: I90961eabf2dcb9ae992aed259088953bad5e4d6d
> ---
>  arch/x86/boot/Makefile                | 1 +
>  arch/x86/boot/compressed/Makefile     | 2 ++
>  arch/x86/entry/vdso/Makefile          | 3 +++
>  arch/x86/kernel/Makefile              | 4 ++++
>  arch/x86/kernel/cpu/Makefile          | 1 +
>  arch/x86/mm/Makefile                  | 3 +++
>  arch/x86/realmode/rm/Makefile         | 1 +
>  drivers/firmware/efi/libstub/Makefile | 1 +
>  kernel/Makefile                       | 1 +
>  kernel/locking/Makefile               | 4 ++++
>  lib/Makefile                          | 1 +
>  11 files changed, 22 insertions(+)
>
> diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
> index d7aa1c3a6b25a..2ca8b9b478f3a 100644
> --- a/arch/x86/boot/Makefile
> +++ b/arch/x86/boot/Makefile
> @@ -12,6 +12,7 @@
>  # Sanitizer runtimes are unavailable and cannot be linked for early boot code.
>  KASAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
> +KMSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
>
>  # Kernel does not boot with kcov instrumentation here.
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 7619742f91c9a..2af62067a90ec 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -20,6 +20,8 @@
>  # Sanitizer runtimes are unavailable and cannot be linked for early boot code.
>  KASAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
> +# KMSAN doesn't work for i386
> +KMSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
>
>  # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index ecf6128c95516..e2b1b9be89ab7 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -13,6 +13,9 @@ KBUILD_CFLAGS += $(DISABLE_LTO)
>
>  # Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE                 := n
> +KMSAN_SANITIZE_vclock_gettime.o := n
> +KMSAN_SANITIZE_vgetcpu.o       := n
> +
>  UBSAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 1ee83df407e3b..a3b7b0452c817 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -32,6 +32,10 @@ KASAN_SANITIZE_paravirt.o                            := n
>  # by several compilation units. To be safe, disable all instrumentation.
>  KCSAN_SANITIZE := n
>
> +# Work around reboot loop.
> +KMSAN_SANITIZE_head$(BITS).o                           := n
> +KMSAN_SANITIZE_nmi.o                                   := n
> +
>  OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o    := y
>  OBJECT_FILES_NON_STANDARD_test_nx.o                    := y
>  OBJECT_FILES_NON_STANDARD_paravirt_patch.o             := y
> diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> index dba6a83bc3493..0e299ba013868 100644
> --- a/arch/x86/kernel/cpu/Makefile
> +++ b/arch/x86/kernel/cpu/Makefile
> @@ -12,6 +12,7 @@ endif
>  # If these files are instrumented, boot hangs during the first second.
>  KCOV_INSTRUMENT_common.o := n
>  KCOV_INSTRUMENT_perf_event.o := n
> +KMSAN_SANITIZE_common.o := n
>
>  # As above, instrumenting secondary CPU boot code causes boot hangs.
>  KCSAN_SANITIZE_common.o := n
> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
> index f7fd0e868c9c8..f11848633cf5b 100644
> --- a/arch/x86/mm/Makefile
> +++ b/arch/x86/mm/Makefile
> @@ -11,6 +11,9 @@ KASAN_SANITIZE_mem_encrypt_identity.o := n
>  # reference __initdata sections.
>  KCSAN_SANITIZE := n
>
> +# Avoid recursion by not calling KMSAN hooks for CEA code.
> +KMSAN_SANITIZE_cpu_entry_area.o := n
> +
>  ifdef CONFIG_FUNCTION_TRACER
>  CFLAGS_REMOVE_mem_encrypt.o            = -pg
>  CFLAGS_REMOVE_mem_encrypt_identity.o   = -pg
> diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
> index 83f1b6a56449f..f614009d3e4e2 100644
> --- a/arch/x86/realmode/rm/Makefile
> +++ b/arch/x86/realmode/rm/Makefile
> @@ -10,6 +10,7 @@
>  # Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
> +KMSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
>
>  # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index dd31237fba2e9..2cf047a0d2e06 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -36,6 +36,7 @@ GCOV_PROFILE                  := n
>  # Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE                 := n
>  KCSAN_SANITIZE                 := n
> +KMSAN_SANITIZE                 := n
>  UBSAN_SANITIZE                 := n
>  OBJECT_FILES_NON_STANDARD      := y
>
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 6ac453daf500e..e9093daf41056 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -35,6 +35,7 @@ KCOV_INSTRUMENT_stacktrace.o := n
>  KCOV_INSTRUMENT_kcov.o := n
>  KASAN_SANITIZE_kcov.o := n
>  KCSAN_SANITIZE_kcov.o := n
> +KMSAN_SANITIZE_kcov.o := n
>  CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
>
>  # cond_syscall is currently not LTO compatible
> diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
> index 6d11cfb9b41f2..1dd1f7d81e691 100644
> --- a/kernel/locking/Makefile
> +++ b/kernel/locking/Makefile
> @@ -3,6 +3,10 @@
>  # and is generally not a function of system call inputs.
>  KCOV_INSTRUMENT                := n
>
> +# Instrumenting lockdep.c with KMSAN may cause deadlocks because of
> +# recursive KMSAN runtime calls.
> +KMSAN_SANITIZE_lockdep.o := n
> +
>  obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
>
>  # Avoid recursion lockdep -> KCSAN -> ... -> lockdep.
> diff --git a/lib/Makefile b/lib/Makefile
> index d8058c5c05826..6ec959b62a55f 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -234,6 +234,7 @@ obj-$(CONFIG_IRQ_POLL) += irq_poll.o
>  CFLAGS_stackdepot.o += -fno-builtin
>  obj-$(CONFIG_STACKDEPOT) += stackdepot.o
>  KASAN_SANITIZE_stackdepot.o := n
> +KMSAN_SANITIZE_stackdepot.o := n
>  KCOV_INSTRUMENT_stackdepot.o := n
>
>  libfdt_files = fdt.o fdt_ro.o fdt_wip.o fdt_rw.o fdt_sw.o fdt_strerror.o \
> --
> 2.25.1.696.g5e7596f4ac-goog
>