linux-kernel - Re: [PATCH v2 2/2] x86/KASLR/64: Determine kernel text mapping size at runtime

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Message-ID: <20161210122757.GE1034@x1>
Date:   Sat, 10 Dec 2016 20:27:57 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     linux-kernel@...r.kernel.org, tglx@...utronix.de, hpa@...or.com,
        mingo@...hat.com, x86@...nel.org, keescook@...omium.org,
        yinghai@...nel.org, thgarnie@...gle.com, kuleshovmail@...il.com,
        luto@...nel.org, mcgrof@...nel.org, anderson@...hat.com,
        dyoung@...hat.com, xlpang@...hat.com
Subject: Re: [PATCH v2 2/2] x86/KASLR/64: Determine kernel text mapping size
 at runtime

On 12/10/16 at 11:31am, Borislav Petkov wrote:
> On Fri, Dec 09, 2016 at 10:41:58PM +0800, Baoquan He wrote:
> > X86 64 kernel takes KERNEL_IMAGE_SIZE as the kernel text mapping size,
> > and it's fixed as compiling time, changing from 512M to 1G as long as
> > CONFIG_RANDOMIZE_BASE is enabled, though people specify kernel option
> > "nokaslr" explicitly.
> > 
> > This could be a wrong behaviour.
> 
> A bunch of changes just because "this could be a wrong behavior". I'm
> not really persuaded.


Well, then apologize for this wrong expression. It should be "This is
a wrong behaviour."

Whether CONFIG_RANDOMIZE_BASE is yes or not, with 'nokaslr' specified,
Kernel text mapping size should be 512M, just the same as no kaslr code
compiled in.

Thanks
Baoquan