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

Knut Omang
2019-08-14T05:51:11Z

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?

What I am trying to do is to build kernel **and** user mode components
under tools/testing/selftests/ktf and to keep the kernel test code out
of the tree. The only way I was able to do this was by means of the module build,
eg. 'make TARGETS="ktf" kselftest' will cause a toplevel 'make M=tools/testing/selftests/ktf'
which is what builds the lot. One can argue that this is a misuse of that mechanism,
but as I argue in the cover letter, I think there is a need to make it possible
to have kernel code that is not going to be part of the installed kernel
somewhere else than in the normal build path of the kernel, which is what
I am trying to achieve.

The toplevel Makefile logic for this is in patch 17 of the series in
tools/testing/selftests/ktf/Makefile
and for ktf/kernel/Makefile and ktf/lib/Makefile and ktf/user/Makefile
in patches 2, 12 and 16 respectively.

It is a bit of a hack still, since the hostcxxprogs-y and hostcxxlib-y
targets in ktf/user and ktf/lib do not get invoked "automatically"
from __build like the obj-m targets. I haven't been able to figure out
yet how to achieve that, and was hoping I could get help on it :-)

Thanks!
Knut

> > > 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=arm-linux-gnueabihf- 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
>
>
>
>
>
>
>