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    Subject[PATCH 5.2 116/313] powerpc/Makefile: Always pass --synthetic to nm if supported
    Date
    From: Michael Ellerman <mpe@ellerman.id.au>

    [ Upstream commit 117acf5c29dd89e4c86761c365b9724dba0d9763 ]

    Back in 2004 we added logic to arch/ppc64/Makefile to pass
    the --synthetic option to nm, if it was supported by nm.

    Then in 2005 when arch/ppc64 and arch/ppc were merged, the logic to
    add --synthetic was moved inside an #ifdef CONFIG_PPC64 block within
    arch/powerpc/Makefile, and has remained there since.

    That was fine, though crufty, until recently when a change to
    init/Kconfig added a config time check that uses $(NM). On powerpc
    that leads to an infinite loop because Kconfig uses $(NM) to calculate
    some values, then the powerpc Makefile changes $(NM), which Kconfig
    notices and restarts.

    The original commit that added --synthetic simply said:
    On new toolchains we need to use nm --synthetic or we miss code
    symbols.

    And the nm man page says that the --synthetic option causes nm to:
    Include synthetic symbols in the output. These are special symbols
    created by the linker for various purposes.

    So it seems safe to always pass --synthetic if nm supports it, ie. on
    32-bit and 64-bit, it just means 32-bit kernels might have more
    symbols reported (and in practice I see no extra symbols). Making it
    unconditional avoids the #ifdef CONFIG_PPC64, which in turn avoids the
    infinite loop.

    Debugged-by: Peter Collingbourne <pcc@google.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Will Deacon <will@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/Makefile | 2 --
    1 file changed, 2 deletions(-)

    diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
    index c345b79414a96..403f7e193833a 100644
    --- a/arch/powerpc/Makefile
    +++ b/arch/powerpc/Makefile
    @@ -39,13 +39,11 @@ endif
    uname := $(shell uname -m)
    KBUILD_DEFCONFIG := $(if $(filter ppc%,$(uname)),$(uname),ppc64)_defconfig

    -ifdef CONFIG_PPC64
    new_nm := $(shell if $(NM) --help 2>&1 | grep -- '--synthetic' > /dev/null; then echo y; else echo n; fi)

    ifeq ($(new_nm),y)
    NM := $(NM) --synthetic
    endif
    -endif

    # BITS is used as extension for files which are available in a 32 bit
    # and a 64 bit version to simplify shared Makefiles.
    --
    2.20.1


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