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Date: Thu, 16 May 2019 10:44:28 -0700 From: Stephen Boyd <swboyd@...omium.org> To: Hsin-Yi Wang <hsinyi@...omium.org>, James Morse <james.morse@....com> 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>, Kees Cook <keescook@...omium.org> Subject: Re: [PATCH v3 2/3] arm64: implement update_fdt_pgprot() Quoting James Morse (2019-05-16 10:34:16) > 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! > Doesn't it need to be done in two places? Userspace and also in the kernel when kexec_file_load() is used? At least, I see a bit of code that does kaslr seed updates to the copied dtb in setup_dtb() of arch/arm64/kernel/machine_kexec_file.c that probably needs to get an update for this new property too.
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