linux-kernel - Re: [PATCH 11/13] kconfig: do not use allnoconfig

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Date:   Wed, 31 Mar 2021 11:25:04 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        KP Singh <kpsingh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Terrell <terrelln@...com>,
        Valentin Schneider <valentin.schneider@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        LKML <linux-kernel@...r.kernel.org>, linux-mips@...r.kernel.org
Subject: Re: [PATCH 11/13] kconfig: do not use allnoconfig_y option

On Wed, Mar 31, 2021 at 10:12 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On Sun, Mar 14, 2021 at 04:48:34AM +0900, Masahiro Yamada wrote:
> > allnoconfig_y is a bad hack that sets a symbol to 'y' by allnoconfig.
> >
> > allnoconfig does not mean a minimum set of CONFIG options because a
> > bunch of prompts are hidden by 'if EMBEDDED' or 'if EXPERT', but I do
> > not like to do a workaround this way.
> >
> > Use the pre-existing feature, KCONFIG_ALLCONFIG, to provide a one
> > liner config fragment. CONFIG_EMBEDDED=y is still forced under
> > allnoconfig.
> >
> > No change in the .config file produced by 'make tinyconfig'.
> >
> > The output of 'make allnoconfig' will be changed; we will get
> > CONFIG_EMBEDDED=n because allnoconfig literally sets all symbols to n.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> With this patch in place, mips:allnoconfig fails to build with
> the following error.
>
> Error log:
> WARNING: modpost: vmlinux.o(.text+0x9c70): Section mismatch in reference from the function reserve_exception_space() to the function .meminit.text:memblock_reserve()
> The function reserve_exception_space() references
> the function __meminit memblock_reserve().
> This is often because reserve_exception_space lacks a __meminit
> annotation or the annotation of memblock_reserve is wrong.
> ERROR: modpost: Section mismatches detected.
> Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.
> make[2]: *** [scripts/Makefile.modpost:62: vmlinux.symvers] Error 1
> make[2]: *** Deleting file 'vmlinux.symvers'
> make[1]: *** [Makefile:1292: vmlinux] Error 2
> make: *** [Makefile:222: __sub-make] Error 2

Thanks for the report. I suspect this is related to allnoconfig
disabling CONFIG_ARCH_KEEP_MEMBLOCK, which changes the definition of
__init_memblock in include/linux/memblock.h.

So allnoconfig would unselect CONFIG_ARCH_KEEP_MEMBLOCK, making
__init_memblock equivalent to __meminit triggering the above warning.

arch/mips/Kconfig
14:     select ARCH_KEEP_MEMBLOCK if DEBUG_KERNEL

so DEBUG_KERNEL is probably also disabled by allnoconfig.

commit a8c0f1c634507 ("MIPS: Select ARCH_KEEP_MEMBLOCK if DEBUG_KERNEL
to enable sysfs memblock debug")

probably should drop the `if DEBUG_KERNEL` part.

>
> Guenter
>
> > ---
> >
> >  init/Kconfig                    | 1 -
> >  kernel/configs/tiny-base.config | 1 +
> >  scripts/kconfig/Makefile        | 3 ++-
> >  3 files changed, 3 insertions(+), 2 deletions(-)
> >  create mode 100644 kernel/configs/tiny-base.config
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 46b87ad73f6a..beb8314fdf96 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1769,7 +1769,6 @@ config DEBUG_RSEQ
> >
> >  config EMBEDDED
> >       bool "Embedded system"
> > -     option allnoconfig_y
> >       select EXPERT
> >       help
> >         This option should be enabled if compiling the kernel for
> > diff --git a/kernel/configs/tiny-base.config b/kernel/configs/tiny-base.config
> > new file mode 100644
> > index 000000000000..2f0e6bf6db2c
> > --- /dev/null
> > +++ b/kernel/configs/tiny-base.config
> > @@ -0,0 +1 @@
> > +CONFIG_EMBEDDED=y
> > diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
> > index 7df3c0e4c52e..46f2465177f0 100644
> > --- a/scripts/kconfig/Makefile
> > +++ b/scripts/kconfig/Makefile
> > @@ -102,7 +102,8 @@ configfiles=$(wildcard $(srctree)/kernel/configs/$@ $(srctree)/arch/$(SRCARCH)/c
> >
> >  PHONY += tinyconfig
> >  tinyconfig:
> > -     $(Q)$(MAKE) -f $(srctree)/Makefile allnoconfig tiny.config
> > +     $(Q)KCONFIG_ALLCONFIG=kernel/configs/tiny-base.config $(MAKE) -f $(srctree)/Makefile allnoconfig
> > +     $(Q)$(MAKE) -f $(srctree)/Makefile tiny.config
> >
> >  # CHECK: -o cache_dir=<path> working?
> >  PHONY += testconfig
> > --
> > 2.27.0
> >



-- 
Thanks,
~Nick Desaulniers