linux-kernel - Re: [PATCH] arm64: kaslr: Reserve size of ARM64_MEMSTART

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Message-ID: <BLUPR13MB02892B82F5EB663B2FECF20EDFB40@BLUPR13MB0289.namprd13.prod.outlook.com>
Date:   Tue, 25 Dec 2018 02:30:32 +0000
From:   Yueyi Li <liyueyi@...e.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:     "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "markus@...rhumer.com" <markus@...rhumer.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in
 linear region

Hi Ard,


On 2018/12/24 17:45, Ard Biesheuvel wrote:
> Does the following change fix your issue as well?
>
> index 9b432d9fcada..9dcf0ff75a11 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -447,7 +447,7 @@ void __init arm64_memblock_init(void)
>                   * memory spans, randomize the linear region as well.
>                   */
>                  if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
> -                       range = range / ARM64_MEMSTART_ALIGN + 1;
> +                       range /= ARM64_MEMSTART_ALIGN;
>                          memstart_addr -= ARM64_MEMSTART_ALIGN *
>                                           ((range * memstart_offset_seed) >> 16);
>                  }

Yes, it can fix this also. I just think modify the first *range* 
calculation would be easier to
  grasp, what do you think?



Thanks,
Yueyi