linux-kernel - [PATCH 4.9 01/33] Makefile.extrawarn: Move -Wunaligned-access to W=1

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Date:   Mon, 21 Feb 2022 09:48:54 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: [PATCH 4.9 01/33] Makefile.extrawarn: Move -Wunaligned-access to W=1

From: Nathan Chancellor <nathan@...nel.org>

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@...r.kernel.org
Link: https://github.com/llvm/llvm-project/commit/35737df4dcd28534bd3090157c224c19b501278a
Link: https://github.com/ClangBuiltLinux/linux/issues/1569
Link: https://github.com/ClangBuiltLinux/linux/issues/1576
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
[nathan: Fix conflict due to lack of afe956c577b2d]
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 scripts/Makefile.extrawarn |    1 +
 1 file changed, 1 insertion(+)

--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -71,5 +71,6 @@ KBUILD_CFLAGS += $(call cc-disable-warni
 KBUILD_CFLAGS += $(call cc-disable-warning, format-zero-length)
 KBUILD_CFLAGS += $(call cc-disable-warning, uninitialized)
 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast)
+KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access)
 endif
 endif