linux/lib/Kconfig.kmsan
Alexander Potapenko 83d0edfa04 kmsan: make sure PREEMPT_RT is off
As pointed out by Peter Zijlstra, __msan_poison_alloca() does not play
well with IRQ code when PREEMPT_RT is on, because in that mode even
GFP_ATOMIC allocations cannot be performed.

Fixing this would require making stackdepot completely lockless, which is
quite challenging and may be excessive for the time being.

Instead, make sure KMSAN is incompatible with PREEMPT_RT, like other debug
configs are.

Link: https://lkml.kernel.org/r/20221102110611.1085175-4-glider@google.com
Link: https://lore.kernel.org/lkml/20221025221755.3810809-1-glider@google.com/
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-11-08 15:57:24 -08:00

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# SPDX-License-Identifier: GPL-2.0-only
config HAVE_ARCH_KMSAN
bool
config HAVE_KMSAN_COMPILER
# Clang versions <14.0.0 also support -fsanitize=kernel-memory, but not
# all the features necessary to build the kernel with KMSAN.
depends on CC_IS_CLANG && CLANG_VERSION >= 140000
def_bool $(cc-option,-fsanitize=kernel-memory -mllvm -msan-disable-checks=1)
config KMSAN
bool "KMSAN: detector of uninitialized values use"
depends on HAVE_ARCH_KMSAN && HAVE_KMSAN_COMPILER
depends on SLUB && DEBUG_KERNEL && !KASAN && !KCSAN
depends on !PREEMPT_RT
select STACKDEPOT
select STACKDEPOT_ALWAYS_INIT
help
KernelMemorySanitizer (KMSAN) is a dynamic detector of uses of
uninitialized values in the kernel. It is based on compiler
instrumentation provided by Clang and thus requires Clang to build.
An important note is that KMSAN is not intended for production use,
because it drastically increases kernel memory footprint and slows
the whole system down.
See <file:Documentation/dev-tools/kmsan.rst> for more details.
if KMSAN
config HAVE_KMSAN_PARAM_RETVAL
# -fsanitize-memory-param-retval is supported only by Clang >= 14.
depends on HAVE_KMSAN_COMPILER
def_bool $(cc-option,-fsanitize=kernel-memory -fsanitize-memory-param-retval)
config KMSAN_CHECK_PARAM_RETVAL
bool "Check for uninitialized values passed to and returned from functions"
default y
depends on HAVE_KMSAN_PARAM_RETVAL
help
If the compiler supports -fsanitize-memory-param-retval, KMSAN will
eagerly check every function parameter passed by value and every
function return value.
Disabling KMSAN_CHECK_PARAM_RETVAL will result in tracking shadow for
function parameters and return values across function borders. This
is a more relaxed mode, but it generates more instrumentation code and
may potentially report errors in corner cases when non-instrumented
functions call instrumented ones.
config KMSAN_KUNIT_TEST
tristate "KMSAN integration test suite" if !KUNIT_ALL_TESTS
default KUNIT_ALL_TESTS
depends on TRACEPOINTS && KUNIT
help
Test suite for KMSAN, testing various error detection scenarios,
and checking that reports are correctly output to console.
Say Y here if you want the test to be built into the kernel and run
during boot; say M if you want the test to build as a module; say N
if you are unsure.
endif