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Date:   Wed, 6 Feb 2019 15:17:53 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Julian Stecklina <jsteckli@amazon.de>
Cc:     Julian Stecklina <js@alien8.de>, x86@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, hpa@zytor.com,
        linux-kernel@vger.kernel.org, jschoenh@amazon.de,
        Dave Jiang <dave.jiang@intel.com>,
        Kees Cook <keescook@chromium.org>, Baoquan He <bhe@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] x86/boot: increase maximum number of avoided KASLR
 regions
Message-ID: <20190206141753.GE7314@zn.tnic>
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On Wed, Feb 06, 2019 at 01:50:57PM +0100, Julian Stecklina wrote:
> Because at this point, we are not in a good position to handle an
> unlimited amount of regions.

We could save only the regions which are ok to kaslr into. And we do,
apparently:

static struct slot_area slot_areas[MAX_SLOT_AREA];

but I guess there was a reason to do the mem_avoid thing too instead of
collecting only OK ranges directly. Maybe Kees will know.

> As for the choice of "16", I took our usecase and multiplied it by two.
> FWIW, this could be even larger.

Because our kernel is not fat enough huh?

Btw, you missed a spot:

static unsigned long find_random_phys_addr(unsigned long minimum,
                                           unsigned long image_size)
{
        /* Check if we had too many memmaps. */
        if (memmap_too_large) {
                debug_putstr("Aborted memory entries scan (more than 4 memmap= args)!\n");
								^^^^^^^^^^^^^
-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.