[PATCH v2] kbuild: strip whitespace in cmd_record_mcount findstring

[Joe Lawrence]

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@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >
> > 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.

Regards,

-- Joe

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