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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Kees Cook <keescook@chromium.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Lendacky <Thomas.Lendacky@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [patch 02/15] x86/cpu: Uninline CR4 accessors
In-Reply-To: <20200420090102.GB24518@infradead.org>
References: <20200419203137.214111265@linutronix.de> <20200419203335.856333226@linutronix.de> <20200420090102.GB24518@infradead.org>
Date:   Mon, 20 Apr 2020 19:25:20 +0200
Message-ID: <87v9luax33.fsf@nanos.tec.linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
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Christoph Hellwig <hch@infradead.org> writes:
>> --- a/arch/x86/kernel/cpu/common.c
>> +++ b/arch/x86/kernel/cpu/common.c
>> @@ -387,7 +387,30 @@ void native_write_cr4(unsigned long val)
>>  			  bits_missing);
>>  	}
>>  }
>> -EXPORT_SYMBOL(native_write_cr4);
>> +#if IS_MODULE(CONFIG_LKDTM)
>> +EXPORT_SYMBOL_GPL(native_write_cr4);
>> +#endif
>
> While this is better than what we had before we really need to have
> a discussion on lkdtm - it needs a lot of crap that otherwise wouldn't
> be exported, and I'm really worried about people enabling it and thus
> adding exports even if they are conditional.  Can we force the code
> to be built in require a boot option for it to be activated?

I can live with that :)