commit 1cf5f151d25fcca94689efd91afa0253621fb33a upstream.
-Wunaligned-access is a new warning in clang that is default enabled for arm and arm64 under certain circumstances within the clang frontend (see LLVM commit below). On v5.17-rc2, an ARCH=arm allmodconfig build shows 1284 total/70 unique instances of this warning (most of the instances are in header files), which is quite noisy.
To keep a normal build green through CONFIG_WERROR, only show this warning with W=1, which will allow automated build systems to catch new instances of the warning so that the total number can be driven down to zero eventually since catching unaligned accesses at compile time would be generally useful.
Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19... Link: https://github.com/ClangBuiltLinux/linux/issues/1569 Link: https://github.com/ClangBuiltLinux/linux/issues/1576 Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Masahiro Yamada masahiroy@kernel.org [nathan: Fix conflict due to lack of afe956c577b2d] Signed-off-by: Nathan Chancellor nathan@kernel.org ---
I am not sure how many people are using ToT clang with ARCH=arm on stable but given how noisy this warning can be, I think it is worth applying this to all applicable stable branches.
This applies to 4.9 through 5.4 with 'patch -Np1'.
scripts/Makefile.extrawarn | 1 + 1 file changed, 1 insertion(+)
diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index ca08f2fe7c34..854e2ba9daa2 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -49,6 +49,7 @@ KBUILD_CFLAGS += -Wno-format KBUILD_CFLAGS += -Wno-sign-compare KBUILD_CFLAGS += -Wno-format-zero-length KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) +KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) endif
endif
base-commit: 52871671099d1bb3fca5ed076029e4b937bfc053