Re: [PATCH v4 12/45] kmsan: disable instrumentation of unsupported common kernel code

Marco Elver
2022-07-12T11:55:41Z

On Fri, 1 Jul 2022 at 16:23, Alexander Potapenko <glider@google.com> wrote:
>
> EFI stub cannot be linked with KMSAN runtime, so we disable
> instrumentation for it.
>
> Instrumenting kcov, stackdepot or lockdep leads to infinite recursion
> caused by instrumentation hooks calling instrumented code again.
>
> This patch was previously part of "kmsan: disable KMSAN instrumentation
> for certain kernel parts", but was split away per Mark Rutland's
> request.

The "This patch..." paragraph feels out of place, and feels like it
should be part of a v4 changelog below ---.

> Signed-off-by: Alexander Potapenko <glider@google.com>

Otherwise,

Reviewed-by: Marco Elver <elver@google.com>

> ---
> Link: https://linux-review.googlesource.com/id/I41ae706bd3474f074f6a870bfc3f0f90e9c720f7
> ---
> drivers/firmware/efi/libstub/Makefile | 1 +
> kernel/Makefile | 1 +
> kernel/locking/Makefile | 3 ++-
> lib/Makefile | 1 +
> 4 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index d0537573501e9..81432d0c904b1 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -46,6 +46,7 @@ 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 a7e1f49ab2b3b..e47f0526c987f 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -38,6 +38,7 @@ KCOV_INSTRUMENT_kcov.o := n
> KASAN_SANITIZE_kcov.o := n
> KCSAN_SANITIZE_kcov.o := n
> UBSAN_SANITIZE_kcov.o := n
> +KMSAN_SANITIZE_kcov.o := n
> CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
>
> # Don't instrument error handlers
> diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
> index d51cabf28f382..ea925731fa40f 100644
> --- a/kernel/locking/Makefile
> +++ b/kernel/locking/Makefile
> @@ -5,8 +5,9 @@ KCOV_INSTRUMENT := n
>
> obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
>
> -# Avoid recursion lockdep -> KCSAN -> ... -> lockdep.
> +# Avoid recursion lockdep -> sanitizer -> ... -> lockdep.
> KCSAN_SANITIZE_lockdep.o := n
> +KMSAN_SANITIZE_lockdep.o := n
>
> ifdef CONFIG_FUNCTION_TRACER
> CFLAGS_REMOVE_lockdep.o = $(CC_FLAGS_FTRACE)
> diff --git a/lib/Makefile b/lib/Makefile
> index f99bf61f8bbc6..5056769d00bb6 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -272,6 +272,7 @@ obj-$(CONFIG_POLYNOMIAL) += polynomial.o
> CFLAGS_stackdepot.o += -fno-builtin
> obj-$(CONFIG_STACKDEPOT) += stackdepot.o
> KASAN_SANITIZE_stackdepot.o := n
> +KMSAN_SANITIZE_stackdepot.o := n
> KCOV_INSTRUMENT_stackdepot.o := n
>
> obj-$(CONFIG_REF_TRACKER) += ref_tracker.o
> --
> 2.37.0.rc0.161.g10f37bed90-goog
>