linux-kernel - Re: building in 32bit chroot on x86

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Date:   Wed, 6 Jun 2018 12:31:10 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     tmb@...eia.org, Ulf Magnusson <ulfalizer@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: building in 32bit chroot on x86_64 host broken

Hi Linus,

2018-06-06 11:19 GMT+09:00 Linus Torvalds <torvalds@...ux-foundation.org>:
> On Tue, Jun 5, 2018 at 6:54 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> But once you *have* that particular Kconfig, I do think that "make
>> oldconfig" should just work. And it apparently used to.
>>
>> So I think this is a behavioral regression.
>
> That doesn't necessarily mean that he fix should be to revert.


If this is a regression, I am OK with the revert,
and it is the only quick solution.



> Maybe the fix is to simply change how we generate the ARCH variable.
>
> Right now, in the Makefile, it is
>
>     ARCH ?= $(SUBARCH)
>
> so basically "if the user didn't specify ARCH, we pick it from SUBARCH".
>
> But that doesn't make much sense for "make oldconfig" does it?
>
> So maybe we could make the rule be that if the user didn't specify
> ARCH explicitly, we take it from SUBARCH, _except_ if we are doing
> "make oldconfig", in which case we take it from the .config file.
>
> That makes a certain amount of sense, wouldn't you agree? Doing
> "oldconfig" and silently changing ARCH under the user seems pretty
> user-hostile.
>
> In fact, I think it would _always_ make sense to take ARCH from the
> config file, _unless_ we're actively generating a new config file
> entirely (ie "make *config", not counting "oldconfig").
>
> Hmm?
>
>                 Linus


This is a big hammer.

It is difficult to make a quick answer.


In fact, I saw a patch series a few years ago.

https://lkml.org/lkml/2014/9/1/70

It was not accepted.
(I was not a maintainer at that time)

I do not remember the details,
but I thought it was a double-edged sword.




-- 
Best Regards
Masahiro Yamada