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    Subject[PATCH AUTOSEL 5.4 17/58] MIPS: vdso: Wrap -mexplicit-relocs in cc-option
    Date
    From: Nathan Chancellor <natechancellor@gmail.com>

    [ Upstream commit 72cf3b3df423c1bbd8fa1056fed009d3a260f8a9 ]

    Clang does not support this option and errors out:

    clang-11: error: unknown argument: '-mexplicit-relocs'

    Clang does not appear to need this flag like GCC does because the jalr
    check that was added in commit 976c23af3ee5 ("mips: vdso: add build
    time check that no 'jalr t9' calls left") passes just fine with

    $ make ARCH=mips CC=clang CROSS_COMPILE=mipsel-linux-gnu- malta_defconfig arch/mips/vdso/

    even before commit d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in
    vdso code").

    -mrelax-pic-calls has been supported since clang 9, which is the
    earliest version that could build a working MIPS kernel, and it is the
    default for clang so just leave it be.

    Fixes: d3f703c4359f ("mips: vdso: fix 'jalr t9' crash in vdso code")
    Link: https://github.com/ClangBuiltLinux/linux/issues/890
    Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
    Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
    Tested-by: Nick Desaulniers <ndesaulniers@google.com>
    Signed-off-by: Paul Burton <paulburton@kernel.org>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: linux-mips@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Cc: clang-built-linux@googlegroups.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/mips/vdso/Makefile | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
    index 08c835d48520b..3dcfdee678fb9 100644
    --- a/arch/mips/vdso/Makefile
    +++ b/arch/mips/vdso/Makefile
    @@ -29,7 +29,7 @@ endif
    cflags-vdso := $(ccflags-vdso) \
    $(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
    -O3 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
    - -mrelax-pic-calls -mexplicit-relocs \
    + -mrelax-pic-calls $(call cc-option, -mexplicit-relocs) \
    -fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
    $(call cc-option, -fno-asynchronous-unwind-tables) \
    $(call cc-option, -fno-stack-protector)
    --
    2.20.1
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