Re: [PATCH 11/13] kconfig: do not use allnoconfig_y option

From: Guenter Roeck <linux@roeck-us.net>
To: Nick Desaulniers <ndesaulniers@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Howells <dhowells@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	KP Singh <kpsingh@google.com>, Kees Cook <keescook@chromium.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Terrell <terrelln@fb.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mips@vger.kernel.org
Subject: Re: [PATCH 11/13] kconfig: do not use allnoconfig_y option
Date: Mon, 5 Apr 2021 07:56:30 -0700	[thread overview]
Message-ID: <1e4295c5-9008-e161-c74e-19a317a562b4@roeck-us.net> (raw)
In-Reply-To: <CAKwvOdmNUMJTjyc7hAhNRzmWmRQa5TCayTSpwiiVnO4HH-YTOQ@mail.gmail.com>

On 3/31/21 11:25 AM, Nick Desaulniers wrote:
> On Wed, Mar 31, 2021 at 10:12 AM Guenter Roeck <linux@roeck-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@kernel.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.
> 

Agreed.

Guenter

>>
>> 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
>>>
> 
> 
> 