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SubjectRe: [PATCH v2] kbuild: strip whitespace in cmd_record_mcount findstring
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
>
>

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