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Date:   Thu, 16 May 2019 18:34:16 +0100
From:   James Morse <james.morse@....com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Miles Chen <miles.chen@...iatek.com>,
        Andrew Murray <andrew.murray@....com>,
        Mark Rutland <mark.rutland@....com>,
        Jun Yao <yaojun8558363@...il.com>, Yu Zhao <yuzhao@...gle.com>,
        Robin Murphy <robin.murphy@....com>,
        Laura Abbott <labbott@...hat.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v3 2/3] arm64: implement update_fdt_pgprot()

Hi!

On 16/05/2019 17:48, Hsin-Yi Wang wrote:
> On Thu, May 16, 2019 at 11:32 PM Rob Herring <robh+dt@...nel.org> wrote:
>> Doesn't kexec operate on a copy because it already does modifications.

It does!

> This patch is to assist "[PATCH v3 3/3] fdt: add support for rng-seed"
> (https://lkml.org/lkml/2019/5/16/257). I thought that by default
> second kernel would use original fdt, so I write new seed back to
> original fdt. Might be wrong.
> 
> ** "[PATCH v3 3/3] fdt: add support for rng-seed" is supposed to
> handle for adding new seed in kexec case, discussed in v2
> (https://lkml.org/lkml/2019/5/13/425)
> 
> By default (not considering user defines their own fdt), if second
> kernel uses copied fdt, when is it copied and can we modify that?

Regular kexec's user-space already updates the dtb for the cmdline and maybe the initrd.
For KASLR, it generates its own seed with getrandom():

https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/tree/kexec/arch/arm64/kexec-arm64.c#n483

If user-space can do it, user-space should do it!


Thanks,

James

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