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kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7
commit16fd20aa98
upstream. When building using GCC 4.7 or older, -ffunction-sections & the -pg flag used by ftrace are incompatible. This causes warnings or build failures (where -Werror applies) such as the following: arch/mips/generic/init.c: error: -ffunction-sections disabled; it makes profiling impossible This used to be taken into account by the ordering of calls to cc-option from within the top-level Makefile, which was introduced by commit90ad4052e8
("kbuild: avoid conflict between -ffunction-sections and -pg on gcc-4.7"). Unfortunately this was broken when the CONFIG_LD_DEAD_CODE_DATA_ELIMINATION cc-option check was moved to Kconfig in commite85d1d65cd
("kbuild: test dead code/data elimination support in Kconfig"), because the flags used by this check no longer include -pg. Fix this by not allowing CONFIG_LD_DEAD_CODE_DATA_ELIMINATION to be enabled at the same time as ftrace/CONFIG_FUNCTION_TRACER when building using GCC 4.7 or older. Signed-off-by: Paul Burton <paul.burton@mips.com> Fixes:e85d1d65cd
("kbuild: test dead code/data elimination support in Kconfig") Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1102,6 +1102,7 @@ config LD_DEAD_CODE_DATA_ELIMINATION
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bool "Dead code and data elimination (EXPERIMENTAL)"
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depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
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depends on EXPERT
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depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
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depends on $(cc-option,-ffunction-sections -fdata-sections)
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depends on $(ld-option,--gc-sections)
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help
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