linux-kernel - Re: Compiling with old gcc breaks when CONFIG

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Message-ID: <5e7dfdc9-8680-91f6-4d7e-aa14fbb6def8@oracle.com>
Date:   Tue, 4 Dec 2018 21:57:22 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:     Meelis Roos <mroos@...ux.ee>, Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Cc:     LKML <linux-kernel@...r.kernel.org>, yamada.masahiro@...ionext.com
Subject: Re: Compiling with old gcc breaks when CONFIG_RETPOLINE is off

Since commit '315bab4e972d kbuild: fix endless syncconfig in case arch 
Makefile sets CROSS_COMPILE',

arch/$(SRCARCH)/Makefile is moved ahead of include/config/%.conf 
synchonization in root Makefile.

So all the CONFIG_* option used in arch/$(SRCARCH)/Makefile may have 
stale value if they were just updated in .config.

This looks like an issue. I'm not familiar with kbuild. Ccing Yamada for 
help.


Thanks

Zhenzhong

On 2018/12/4 17:58, Meelis Roos wrote:
> Just tried 4.20-rc5 on an old K6-2 PC with gcc 5.3.1, got an error 
> about non-retpoline compiler,
> turned CONFIG_RETPOLINE off and retried.
>
> To my surprise, compilation still breaks with
> arch/x86/Makefile:224: *** You are building kernel with non-retpoline 
> compiler, please update your compiler..  Stop.
>
> As I read the Makefile, it should error only when CONFIG_RETPOLINE is 
> enabled, but it still breaks.
>
> $ grep -r CONFIG_RETPOLINE .config
> # CONFIG_RETPOLINE is not set
>
> $ grep -r CONFIG_RETPOLINE include/
> include/generated/autoconf.h:#define CONFIG_RETPOLINE 1
> include/config/auto.conf:CONFIG_RETPOLINE=y
>
> So the headers have not been updated yet, maybe?
>