From: Arnd Bergmann <[email protected]> Testing randconfig builds on s390 with gcc-15, I came across a number of seemingly unrelated build failures that ended up all being caused by the -fsanitize=alignment option:
s390-linux-ld: kernel/sched/build_policy.o: in function `thread_group_cputime': include/linux/seqlock.h:1286:(.text+0x1f738): undefined reference to `__scoped_seqlock_bug' lib/tests/overflow_kunit.c: In function 'same_type_test': lib/tests/overflow_kunit.c:1008:13: note: variable tracking size limit exceeded with '-fvar-tracking-assignments', retrying without fs/fat/fat_test.c: In function 'fat_clus_to_blknr_test': fs/fat/fat_test.c:33:1: error: the frame size of 4736 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] lib/crypto/chacha-block-generic.c: In function 'chacha_permute': lib/crypto/chacha-block-generic.c:65:1: error: the frame size of 2000 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] lib/crypto/sha3.c: In function 'sha3_keccakf_generic': lib/crypto/sha3.c:175:1: error: the frame size of 2248 bytes is larger than 1536 bytes [-Werror=frame-larger-than=] lib/zstd/decompress/huf_decompress.c: In function 'HUF_decompress4X2_usingDTable_internal_default': lib/zstd/decompress/huf_decompress.c:1512:1: error: the frame size of 1352 bytes is larger than 1280 bytes [-Werror=frame-larger-than=] What I observe here is a huge increase in generated calls to __ubsan_handle_type_mismatch_v1() that ends up thowing off a number of compiler optimizations that the kernel relies on. I have not been able to figure out why this happens on s390 but not arm64, arm or x86, if other toolchain versions are affected by the same thing, and if this is a problem in gcc or in the kernel itself, e.g. some variable being identified as unaligned when it should be aligned. This clearly needs more investigation to figure out properly what is going on, but turning it off is currently required for randconfig testing. Cc: Kees Cook <[email protected]> Cc: Marco Elver <[email protected]> Cc: Andrey Konovalov <[email protected]> Cc: Andrey Ryabinin <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Heiko Carstens <[email protected]> Cc: Vasily Gorbik <[email protected]> Cc: Alexander Gordeev <[email protected]> Cc: Christian Borntraeger <[email protected]> Cc: Sven Schnelle <[email protected]> Cc: [email protected] Signed-off-by: Arnd Bergmann <[email protected]> --- lib/Kconfig.ubsan | 1 + 1 file changed, 1 insertion(+) diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan index 1ecaae7064d2..3fc03a6b5af4 100644 --- a/lib/Kconfig.ubsan +++ b/lib/Kconfig.ubsan @@ -152,6 +152,7 @@ config UBSAN_ENUM config UBSAN_ALIGNMENT bool "Perform checking for misaligned pointer usage" + depends on !S390 || BROKEN default !HAVE_EFFICIENT_UNALIGNED_ACCESS depends on !UBSAN_TRAP && !COMPILE_TEST depends on $(cc-option,-fsanitize=alignment) -- 2.39.5
