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authorNathan Chancellor <nathan@kernel.org>2022-03-31 01:45:27 +0200
committerMasahiro Yamada <masahiroy@kernel.org>2022-04-01 17:05:28 +0200
commitcf300b83c793c25c6b485fdaf7a4447d8ea4c655 (patch)
treef094949a5a81b095c6073c630450f1a5e33adc12 /Makefile
parentkbuild: fix empty ${PYTHON} in scripts/link-vmlinux.sh (diff)
downloadlinux-cf300b83c793c25c6b485fdaf7a4447d8ea4c655.tar.xz
linux-cf300b83c793c25c6b485fdaf7a4447d8ea4c655.zip
kbuild: Remove '-mno-global-merge'
This flag is specific to clang, where it is only used by the 32-bit and 64-bit ARM backends. In certain situations, the presence of this flag will cause a warning, as shown by commit 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS"). Since commit 61163efae020 ("kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang") that added this flag back in 2014, there have been quite a few changes to the GlobalMerge pass in LLVM. Building several different ARCH=arm and ARCH=arm64 configurations with LLVM 11 (minimum) and 15 (current main version) with this flag removed (i.e., with the default of '-mglobal-merge') reveals no modpost warnings, so it is likely that the issue noted in the comment is no longer relevant due to changes in LLVM or modpost, meaning this flag can be removed. If any new warnings show up that are a result of the removal of this flag, it can be added back under arch/arm{,64}/Makefile to avoid warnings on other architectures. Signed-off-by: Nathan Chancellor <nathan@kernel.org> Tested-by: David Gow <davidgow@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile4
1 files changed, 0 insertions, 4 deletions
diff --git a/Makefile b/Makefile
index 18ecb49f1af6..3b3cd75bba87 100644
--- a/Makefile
+++ b/Makefile
@@ -793,10 +793,6 @@ ifdef CONFIG_CC_IS_CLANG
KBUILD_CPPFLAGS += -Qunused-arguments
# The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable.
KBUILD_CFLAGS += -Wno-gnu
-# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
-# source of a reference will be _MergedGlobals and not on of the whitelisted names.
-# See modpost pattern 2
-KBUILD_CFLAGS += -mno-global-merge
else
# gcc inanely warns about local variables called 'main'