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

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Message-ID: <CAK7LNARyD=tG0JhwN_mjdyDRSPAF8UoZKvqAT3Ah_v7GfymCPg@mail.gmail.com>
Date:   Tue, 26 Mar 2019 14:29:47 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicholas Piggin <npiggin@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] kbuild: strip whitespace in cmd_record_mcount findstring

On Tue, Mar 26, 2019 at 1:05 AM 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
>
> 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>
> ---
>
> 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
> --
> 2.20.1
>



I do not see a point in using the shell command here
in the first place.

Instead of adding crappy workarounds,
I guess the following simple code should work:


index 2554a15..5f13021 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -199,11 +199,8 @@ 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)                        \
-       fi
+cmd_record_mcount = $(if $(findstring $(CC_FLAGS_FTRACE),$(_c_flags)),\
+                 $(sub_cmd_record_mcount))
 endif # CC_USING_RECORD_MCOUNT
 endif # CONFIG_FTRACE_MCOUNT_RECORD



-- 
Best Regards
Masahiro Yamada