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    Subject[PATCH 11/21] trace: Use -mcount-record for dynamic ftrace
    Date
    From: Andi Kleen <ak@linux.intel.com>

    gcc 5 supports a new -mcount-record option to generate ftrace
    tables directly. This avoids the need to run record_mcount
    manually.

    Use this option when available.

    So far doesn't use -mcount-nop, which also exists now.

    This is needed to make ftrace work with LTO because the
    normal record-mcount script doesn't run over the link
    time output.

    It should also improve build times slightly in the general
    case.

    Cc: rostedt@goodmis.org
    Signed-off-by: Andi Kleen <ak@linux.intel.com>
    ---
    scripts/Makefile.build | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/scripts/Makefile.build b/scripts/Makefile.build
    index cb8997ed0149..8179563bcd85 100644
    --- a/scripts/Makefile.build
    +++ b/scripts/Makefile.build
    @@ -219,6 +219,11 @@ cmd_modversions_c = \
    endif

    ifdef CONFIG_FTRACE_MCOUNT_RECORD
    +# gcc 5 supports generating the mcount tables directly
    +ifneq ($(call cc-option,-mrecord-mcount,y),y)
    +KBUILD_CFLAGS += -mrecord-mcount
    +else
    +# else do it all manually
    ifdef BUILD_C_RECORDMCOUNT
    ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
    RECORDMCOUNT_FLAGS = -w
    @@ -264,6 +269,7 @@ objtool_args += --no-unreachable
    else
    objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable)
    endif
    +endif

    # 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
    # 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
    --
    2.13.6
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