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x86/boot/compressed: Move CLANG_FLAGS to beginning of KBUILD_CFLAGS

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[ Upstream commit 5fe392ff9d1f7254a1fbb3f72d9893088e4d23eb ]

When cross compiling i386_defconfig on an arm64 host with clang, there
are a few instances of '-Waddress-of-packed-member' and
'-Wgnu-variable-sized-type-not-at-end' in arch/x86/boot/compressed/,
which should both be disabled with the cc-disable-warning calls in that
directory's Makefile, which indicates that cc-disable-warning is failing
at the point of testing these flags.

The cc-disable-warning calls fail because at the point that the flags
are tested, KBUILD_CFLAGS has '-march=i386' without $(CLANG_FLAGS),
which has the '--target=' flag to tell clang what architecture it is
targeting. Without the '--target=' flag, the host architecture (arm64)
is used and i386 is not a valid value for '-march=' in that case. This
error can be seen by adding some logging to try-run:

  clang-14: error: the clang compiler does not support '-march=i386'

Invoking the compiler has to succeed prior to calling cc-option or
cc-disable-warning in order to accurately test whether or not the flag
is supported; if it doesn't, the requested flag can never be added to
the compiler flags. Move $(CLANG_FLAGS) to the beginning of KBUILD_FLAGS
so that any new flags that might be added in the future can be
accurately tested.

Fixes: d5cbd80e302d ("x86/boot: Add $(CLANG_FLAGS) to compressed KBUILD_CFLAGS")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211222163040.1961481-1-nathan@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Nathan Chancellor 2021-12-22 09:30:41 -07:00 committed by Greg Kroah-Hartman
parent 70eec71f32
commit aea5302d9d
1 changed files with 5 additions and 2 deletions
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7
arch/x86/boot/compressed/Makefile
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@ -28,7 +28,11 @@ KCOV_INSTRUMENT := n
targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst
KBUILD_CFLAGS := -m$(BITS) -O2
# CLANG_FLAGS must come before any cc-disable-warning or cc-option calls in
# case of cross compiling, as it has the '--target=' flag, which is needed to
# avoid errors with '-march=i386', and future flags may depend on the target to
# be valid.
KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
cflags-$(CONFIG_X86_32) := -march=i386
@ -46,7 +50,6 @@ KBUILD_CFLAGS += -D__DISABLE_EXPORTS
# Disable relocation relaxation in case the link is not PIE.
KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mrelax-relocations=no)
KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
KBUILD_CFLAGS += $(CLANG_FLAGS)
# sev-es.c indirectly inludes inat-table.h which is generated during
# compilation and stored in $(objtree). Add the directory to the includes so