linux-kernel - Re: [PATCH v1 2/3] selftests/nolibc: fix up O= option support

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Message-Id: <20230804074342.28248-1-falcon@tinylab.org>
Date:   Fri,  4 Aug 2023 15:43:42 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     thomas@...ch.de
Cc:     arnd@...db.de, falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, tanyuan@...ylab.org, w@....eu
Subject: Re: [PATCH v1 2/3] selftests/nolibc: fix up O= option support

Hi, Thomas

> On 2023-08-03 22:45:52+0800, Zhangjin Wu wrote:
> > To avoid pollute the source code tree and avoid mrproper for every
> > architecture switch, the O= argument must be supported.
> > 
> > Both IMAGE and .config are from the building directory, let's use
> > objtree instead of srctree for them.
> > 
> > If no O= option specified, means building kernel in source code tree,
> > objtree should be srctree in such case.
> > 
> > Suggested-by: Willy Tarreau <w@....eu>
> > Link: https://lore.kernel.org/lkml/ZK0AB1OXH1s2xYsh@1wt.eu/
> > Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
> > ---
> >  tools/testing/selftests/nolibc/Makefile | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
> > index 51fef5e6a152..af590aee063a 100644
> > --- a/tools/testing/selftests/nolibc/Makefile
> > +++ b/tools/testing/selftests/nolibc/Makefile
> > @@ -9,6 +9,9 @@ ifeq ($(srctree),)
> >  srctree := $(patsubst %/tools/testing/selftests/,%,$(dir $(CURDIR)))
> >  endif
> >  
> > +# add objtree for O= argument, required by IMAGE and .config
> > +objtree ?= $(srctree)
> 
> Isn't this already set by the included tools/scripts/Makefile.include?
>

Good question, but it is empty if no O= specified, checked it several
times before ;-)

> Also I'm not entirely if O= works as intended currently.
> When using O=foo in the $LINUX/tools/testing/selftests/nolibc directory

It does work, I have used it to test all of the run targets of the
tinyconfig patches like this:

    $ make run O=kernel-$arch RUN_OUT=run.$arch.out ...

Everything about the kernel will be built in $(O).

Just rechecked the O variable in top-level Makefile, selftests/nolibc Makefile
and tools/nolibc Makefile, all of them get the right O value from command line.

>From my Makefile experience, an option from command line will be passed
to every sub Makefile via $(-*-command-variables-*-), it has the highest
priority then the others, except when we use 'override' keyword
internally.

> the build instead is happening in $LINUX/foo. But the Makefile first
> validates that $LINUX/tools/testing/selftests/nolibc/foo exists.
>

Sorry, I didn't get your meaning above?

Do you mean this line:

    srctree := $(patsubst %/tools/testing/selftests/,%,$(dir $(CURDIR)))

by removing tools/testing/selftests/ of curdir's dir (means no nolibc itself),
srctree above is just the top-level kernel source code tree.

> It seems we need to pass $(COMMAND_O) to the recursive calls to $(MAKE),
> too?
>

So, no need to pass O or COMMAND_O.

Thanks,
Zhangjin

> > +
> >  ifeq ($(ARCH),)
> >  include $(srctree)/scripts/subarch.include
> >  ARCH = $(SUBARCH)
> > @@ -217,12 +220,12 @@ kernel: initramfs
> >  
> >  # run the tests after building the kernel
> >  run: kernel
> > -	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> > +	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(objtree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> >  	$(Q)$(REPORT) $(CURDIR)/run.out
> >  
> >  # re-run the tests from an existing kernel
> >  rerun:
> > -	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(srctree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> > +	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(objtree)/$(IMAGE)" -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> >  	$(Q)$(REPORT) $(CURDIR)/run.out
> >  
> >  # report with existing test log
> > -- 
> > 2.25.1
> >