Re: [PATCH v3 2/3] arm64: implement update_fdt_pgprot()

[James Morse]

Hi!

On 16/05/2019 17:48, Hsin-Yi Wang wrote:
> On Thu, May 16, 2019 at 11:32 PM Rob Herring <robh+dt@xxxxxxxxxx> 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