linux-kernel - Re: [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/

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Date:   Wed, 8 Jul 2020 08:52:23 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Haren Myneni <haren@...ibm.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Jiri Kosina <jikos@...nel.org>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>,
        Tal Gilboa <talgi@...lanox.com>, kunit-dev@...glegroups.com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, live-patching@...r.kernel.org
Subject: Re: [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/

On Tue 2020-07-07 18:21:17, Masahiro Yamada wrote:
>   ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> 
> exists here in sub-directories of lib/ to keep the behavior of
> commit 2464a609ded0 ("ftrace: do not trace library functions").
> 
> Since that commit, not only the objects in lib/ but also the ones in
> the sub-directories are excluded from ftrace (although the commit
> description did not explicitly mention this).
> 
> However, most of library functions in sub-directories are not so hot.
> Re-add them to ftrace.
> 
> Going forward, only the objects right under lib/ will be excluded.
 
> diff --git a/lib/livepatch/Makefile b/lib/livepatch/Makefile
> index 9abdf615b088..295b94bff370 100644
> --- a/lib/livepatch/Makefile
> +++ b/lib/livepatch/Makefile
> @@ -2,8 +2,6 @@
>  #
>  # Makefile for livepatch test code.
>  
> -ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
> -
>  obj-$(CONFIG_TEST_LIVEPATCH) += test_klp_atomic_replace.o \
>  				test_klp_callbacks_demo.o \
>  				test_klp_callbacks_demo2.o \

With this change it might be possible to remove also the last few
lines that explicitly added $(CC_FLAGS_FTRACE) for two test modules.

The two modules really needed these flags. But they are fine also
for the other modules.

We could do this later as a followup patch but it would be nice
to do so here.

Best Regards,
Petr

PS: BTW: The livepatch selftests fail in Linus's master now. But it
seems to be for another reason. I am going to dig into it.