linux/lib/Kconfig.ubsan
Anders Roxell 1a6a1dbeb7 lib/ubsan: default UBSAN_ALIGNMENT to not set
When booting an allmodconfig kernel, there are a lot of false-positives.
With a message like this 'UBSAN: Undefined behaviour in...' with a call
trace that follows.

UBSAN warnings are a result of enabling noisy CONFIG_UBSAN_ALIGNMENT
which is disabled by default if HAVE_EFFICIENT_UNALIGNED_ACCESS=y.

It's noisy even if don't have efficient unaligned access, e.g.  people
often add __cacheline_aligned_in_smp in structs, but forget to align
allocations of such struct (kmalloc() give 8-byte alignment in worst
case).

Rework so that when building a allmodconfig kernel that turns everything
into '=m' or '=y' will turn off UBSAN_ALIGNMENT.

[aryabinin@virtuozzo.com: changelog addition]
Link: http://lkml.kernel.org/r/20181217150326.30933-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-07 18:32:02 -08:00

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config ARCH_HAS_UBSAN_SANITIZE_ALL
bool
config UBSAN
bool "Undefined behaviour sanity checker"
help
This option enables undefined behaviour sanity checker
Compile-time instrumentation is used to detect various undefined
behaviours in runtime. Various types of checks may be enabled
via boot parameter ubsan_handle
(see: Documentation/dev-tools/ubsan.rst).
config UBSAN_SANITIZE_ALL
bool "Enable instrumentation for the entire kernel"
depends on UBSAN
depends on ARCH_HAS_UBSAN_SANITIZE_ALL
# We build with -Wno-maybe-uninitilzed, but we still want to
# use -Wmaybe-uninitilized in allmodconfig builds.
# So dependsy bellow used to disable this option in allmodconfig
depends on !COMPILE_TEST
default y
help
This option activates instrumentation for the entire kernel.
If you don't enable this option, you have to explicitly specify
UBSAN_SANITIZE := y for the files/directories you want to check for UB.
Enabling this option will get kernel image size increased
significantly.
config UBSAN_NO_ALIGNMENT
bool "Disable checking of pointers alignment"
depends on UBSAN
default y if HAVE_EFFICIENT_UNALIGNED_ACCESS
help
This option disables the check of unaligned memory accesses.
This option should be used when building allmodconfig.
Disabling this option on architectures that support unaligned
accesses may produce a lot of false positives.
config UBSAN_ALIGNMENT
def_bool !UBSAN_NO_ALIGNMENT
config TEST_UBSAN
tristate "Module for testing for undefined behavior detection"
depends on m && UBSAN
help
This is a test module for UBSAN.
It triggers various undefined behavior, and detect it.