Re: [PATCH v2] kbuild: strip whitespace in cmd_record_mcount findstring

[Nicholas Piggin <npiggin@gmail.com>]

Joe Lawrence's on March 27, 2019 3:33 am:
> On Tue, Mar 26, 2019 at 02:29:47PM +0900, Masahiro Yamada wrote:
>> On Tue, Mar 26, 2019 at 1:05 AM Joe Lawrence <joe.lawrence@redhat.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@redhat.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
>> 
> 
> Hi Masahiro,
> 
> Agreed on the shell command ugliness, however I still think we need to
> strip the search pattern here.  With your suggestion:
> 
> % rm -f kernel/trace/trace_selftest_dynamic.o 
> % make kernel/trace/trace_selftest_dynamic.o
>   CALL    scripts/checksyscalls.sh
>   CALL    scripts/atomic/check-atomics.sh
>   CC      kernel/trace/trace_selftest_dynamic.o
> 
> % eu-readelf --sections kernel/trace/trace_selftest_dynamic.o | grep mcount
> (nothing)
> 
> Adding it back as, as below, restores those sections and the self tests
> work again.

Thanks for finding and fixing this, nice work!

Thanks,
Nick

> 
> Regards,
> 
> -- Joe
> 
> -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8-- -->8--
> 
> From 6a85e8ecf4179b3e80601a327ec43d8d49f0e3cd Mon Sep 17 00:00:00 2001
> From: Joe Lawrence <joe.lawrence@redhat.com>
> Date: Tue, 26 Mar 2019 10:50:28 -0400
> Subject: [PATCH v2] kbuild: strip whitespace in cmd_record_mcount findstring
> 
> 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.
> 
> Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com> (refactoring)
> Fixes: 6977f95e63b9 ("powerpc: avoid -mno-sched-epilog on GCC 4.9 and newer").
> Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
> ---
>  scripts/Makefile.build | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 2554a15ecf2b..76ca30cc4791 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 $(strip $(CC_FLAGS_FTRACE)),$(_c_flags)),	\
> +	$(sub_cmd_record_mcount))
>  endif # CC_USING_RECORD_MCOUNT
>  endif # CONFIG_FTRACE_MCOUNT_RECORD
>  
> -- 
> 2.20.1
> 
>