linux-kernel - Re: [PATCH] kbuild: strip whitespace in cmd_record

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Date:   Mon, 25 Mar 2019 12:21:20 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     linux-kbuild@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH] kbuild: strip whitespace in cmd_record_mcount
 findstring

On Mon, 25 Mar 2019 12:04:38 -0400
Joe Lawrence <joe.lawrence@...hat.com> wrote:

> CC_FLAGS_FTRACE may contain trailing whitespace that interferes with
> findstring.
> 
> For example, commit 6977f95e63b9 ("powerpc: avoid -mno-sched-epilog on
> GCC 4.9 and newer") introduced a change such that on my ppc64le box,
> CC_FLAGS_FTRACE="-pg -mprofile-kernel ".  (Note the trailing space.)
> When cmd_record_mcount is now invoked, findstring fails as the ftrace
> flags were found at very end of _c_flags, without the trailing space.
> 
>   _c_flags=" ... -pg -mprofile-kernel"
>   CC_FLAGS_FTRACE="-pg -mprofile-kernel "
>                                        ^
>     findstring is looking for this extra space

Wow, what a bug.

> 
> Remove the redundant whitespaces from CC_FLAGS_FTRACE in
> cmd_record_mcount to avoid this problem.
> 
> Fixes: 6977f95e63b9 ("powerpc: avoid -mno-sched-epilog on GCC 4.9 and newer").
> Signed-off-by: Joe Lawrence <joe.lawrence@...hat.com>

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
> 
> Standard disclaimer: I'm not a kbuild expert, but this works around the
> problem I reported where ftrace and livepatch self-tests were failing as
> specified object files were not run through the recordmcount.pl script:
> 
> ppc64le: ftrace self-tests and $(CC_FLAGS_FTRACE) broken?
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2019-March/187298.html
> 
>  scripts/Makefile.build | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 2554a15ecf2b..74d402b5aa3c 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -199,10 +199,10 @@ sub_cmd_record_mcount = perl $(srctree)/scripts/recordmcount.pl "$(ARCH)" \
>  	"$(if $(part-of-module),1,0)" "$(@)";
>  recordmcount_source := $(srctree)/scripts/recordmcount.pl
>  endif # BUILD_C_RECORDMCOUNT
> -cmd_record_mcount =						\
> -	if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" =	\
> -	     "$(CC_FLAGS_FTRACE)" ]; then			\
> -		$(sub_cmd_record_mcount)			\
> +cmd_record_mcount =							\
> +	if [ "$(findstring $(strip $(CC_FLAGS_FTRACE)),$(_c_flags))" =	\
> +	     "$(strip $(CC_FLAGS_FTRACE))" ]; then			\
> +		$(sub_cmd_record_mcount)				\
>  	fi
>  endif # CC_USING_RECORD_MCOUNT
>  endif # CONFIG_FTRACE_MCOUNT_RECORD