Re: [RFC 01/19] kbuild: Fixes to rules for host-cshlib and host-cxxshlib

Masahiro Yamada
2019-08-21T01:48:11Z

On Wed, Aug 14, 2019 at 9:53 PM Knut Omang <knut.omang@oracle.com> wrote:
>
> On Wed, 2019-08-14 at 07:52 +0200, Knut Omang wrote:
> > On Wed, 2019-08-14 at 11:02 +0900, Masahiro Yamada wrote:
> > > Hi Knut,
> > >
> > > On Wed, Aug 14, 2019 at 1:19 AM Knut Omang <knut.omang@oracle.com> wrote:
> > > > On Tue, 2019-08-13 at 23:01 +0900, Masahiro Yamada wrote:
> > > > > On Tue, Aug 13, 2019 at 3:13 PM Knut Omang <knut.omang@oracle.com> wrote:
> > > > > > C++ libraries interfacing to C APIs might sometimes need some glue
> > > > > > logic more easily written in C.
> > > > > > Allow a C++ library to also contain 0 or more C objects.
> > > > > >
> > > > > > Also fix rules for both C and C++ shared libraries:
> > > > > > - C++ shared libraries depended on .c instead of .cc files
> > > > > > - Rules were referenced as -objs instead of the intended
> > > > > > -cobjs and -cxxobjs following the pattern from hostprogs*.
> > > > > >
> > > > > > Signed-off-by: Knut Omang <knut.omang@oracle.com>
> > > > >
> > > > > How is this patch related to the rest of this series?
> > > >
> > > > This is just my (likely naive) way I to get what I had working
> > > > using autotools in the Github version of KTF) translated into something
> > > > comparable using kbuild only. We need to build a shared library consisting
> > > > of a few C++ files and a very simple C file, and a couple of simple binaries,
> > > > and the rule in there does seem to take .c files and subject them to the
> > > > C++ compiler, which makes this difficult to achieve?
> > >
> > > Looking at the diff stat of the cover-letter,
> > > the rest of this patch series is touching only
> > > Documentation/ and tools/testing/kselftests/.
> > >
> > > So, this one is unused by the rest of the changes, isn't it?
> > > Am I missing something?
> > >
> > >
> > >
> > > > > This patch breaks GCC-plugins.
> > > > > Did you really compile-test this patch before the submission?
> > > >
> > > > Sorry for my ignorance here:
> > > > I ran through the kernel build and installed the resulting kernel
> > > > on a VM that I used to test this, if that's what you are asking
> > > > about?
> > > >
> > > > Do I need some unusual .config options or run a special make target
> > > > to trigger the problem you see?
> > > >
> > > > I used a recent Fedora config with default values for new options,
> > > > and ran the normal default make target (also with O=) and make selftests
> > > > to test the patch itself.
> > >
> > > I just built allmodconfig for arm.
> > >
> > > (The 0-day bot tests allmodconfig for most of architectures,
> > > so you may receive error reports anyway.)
> > >
> > >
> > > With your patch, I got the following:
> > >
> > >
> > > masahiro@grover:~/ref/linux$ make ARCH=arm
> > > CROSS_COMPILE=- allmodconfig all
> > > HOSTCC scripts/basic/fixdep
> > > HOSTCC scripts/kconfig/conf.o
> > > HOSTCC scripts/kconfig/confdata.o
> > > HOSTCC scripts/kconfig/expr.o
> > > LEX scripts/kconfig/lexer.lex.c
> > > YACC scripts/kconfig/parser.tab.h
> > > HOSTCC scripts/kconfig/lexer.lex.o
> > > YACC scripts/kconfig/parser.tab.c
> > > HOSTCC scripts/kconfig/parser.tab.o
> > > HOSTCC scripts/kconfig/preprocess.o
> > > HOSTCC scripts/kconfig/symbol.o
> > > HOSTLD scripts/kconfig/conf
> > > scripts/kconfig/conf --allmodconfig Kconfig
> > > #
> > > # configuration written to .config
> > > #
> > > SYSHDR arch/arm/include/generated/uapi/asm/unistd-common.h
> > > SYSHDR arch/arm/include/generated/uapi/asm/unistd-oabi.h
> > > SYSHDR arch/arm/include/generated/uapi/asm/unistd-eabi.h
> > > HOSTCC scripts/dtc/dtc.o
> > > HOSTCC scripts/dtc/flattree.o
> > > HOSTCC scripts/dtc/fstree.o
> > > HOSTCC scripts/dtc/data.o
> > > HOSTCC scripts/dtc/livetree.o
> > > HOSTCC scripts/dtc/treesource.o
> > > HOSTCC scripts/dtc/srcpos.o
> > > HOSTCC scripts/dtc/checks.o
> > > HOSTCC scripts/dtc/util.o
> > > LEX scripts/dtc/dtc-lexer.lex.c
> > > YACC scripts/dtc/dtc-parser.tab.h
> > > HOSTCC scripts/dtc/dtc-lexer.lex.o
> > > YACC scripts/dtc/dtc-parser.tab.c
> > > HOSTCC scripts/dtc/dtc-parser.tab.o
> > > HOSTCC scripts/dtc/yamltree.o
> > > HOSTLD scripts/dtc/dtc
> > > CC scripts/gcc-plugins/latent_entropy_plugin.o
> > > cc1: error: cannot load plugin ./scripts/gcc-plugins/arm_ssp_per_task_plugin.so
> > > ./scripts/gcc-plugins/arm_ssp_per_task_plugin.so: cannot open
> > > shared object file: No such file or directory
> > > cc1: error: cannot load plugin ./scripts/gcc-plugins/structleak_plugin.so
> > > ./scripts/gcc-plugins/structleak_plugin.so: cannot open shared
> > > object file: No such file or directory
> > > cc1: error: cannot load plugin ./scripts/gcc-plugins/latent_entropy_plugin.so
> > > ./scripts/gcc-plugins/latent_entropy_plugin.so: cannot open shared
> > > object file: No such file or directory
> > > cc1: error: cannot load plugin ./scripts/gcc-plugins/randomize_layout_plugin.so
> > > ./scripts/gcc-plugins/randomize_layout_plugin.so: cannot open
> > > shared object file: No such file or directory
> > > make[3]: *** [scripts/Makefile.build;281:
> > > scripts/gcc-plugins/latent_entropy_plugin.o] Error 1
> > > make[2]: *** [scripts/Makefile.build;497: scripts/gcc-plugins] Error 2
> > > make[1]: *** [Makefile;1097: scripts] Error 2
> > > make: *** [Makefile;330: __build_one_by_one] Error 2
> >
> > Ok, I see!
> >
> > I'll recall this target and look into it!
>
> Ok, so I have tried installing the arm-linux-gnueabihf cross compiler and compiled the kernel for arm,
> but allmodconfig does not seem to enable any GCC plugins per default even on ARM and I haven't been able
> to figure out how to enable any.

Linaro toolchain supports gcc plugins.

https://releases.linaro.org/components/toolchain/binaries/latest-7/arm-linux-gnueabihf/

kernel.org one supports it as well.

https://mirrors.edge.kernel.org/pub/tools/crosstool/

> A plain allmodconfig generated config compiles perfectly for me both native x86 and w/arm cross compile,
> but it doesn't seem to enable any gcc plugins.
>
> Anyway, maybe I am getting this wrong anyway:
> Having played with cross compile, it starts to become clear to me that HOSTCC rules
> might not be the right rules to use, as it will generate host user land binaries as opposed to
> target user land binaries (in a cross compile world obviously these differ)
>
> Now, I started off with using the rules in the selftests makefiles for this, but they do not play that well with
> kernel module building. My goal is to be able to do both user land and kernel module **target** compiles
> from the same subtree. Any hints on how to accomplish this appreciated :-)

tools/ is out of scope of kbuild because it adopted a different (more
adhoc) build system.
I have no idea. Please talk to the kselftest maintainer.

>
> Thanks,
> Knut
>

--
Best Regards
Masahiro Yamada