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kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7
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 commit 90ad405 ("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 commit e85d1d6 ("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 <[email protected]> Fixes: e85d1d6 ("kbuild: test dead code/data elimination support in Kconfig") Reported-by: Geert Uytterhoeven <[email protected]> Cc: Nicholas Piggin <[email protected]> Cc: [email protected] # v4.19+ Signed-off-by: Masahiro Yamada <[email protected]>
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