Subject: [PATCH v30 05/11] arm64: kdump: protect crash dump kernel memory

From: [email-masked] (Mark Rutland)
Date: Fri, 27 Jan 2017 18:56:13 +0000

On Sat, Jan 28, 2017 at 02:15:16AM +0900, AKASHI Takahiro wrote:
> On Fri, Jan 27, 2017 at 11:19:32AM +0000, James Morse wrote:
> > Hi Akashi,
> >
> > On 26/01/17 11:28, AKASHI Takahiro wrote:
> > > On Wed, Jan 25, 2017 at 05:37:38PM +0000, James Morse wrote:
> > >> On 24/01/17 08:49, AKASHI Takahiro wrote:
> > >>> To protect the memory reserved for crash dump kernel once after loaded,
> > >>> arch_kexec_protect_crashres/unprotect_crashres() are meant to deal with
> > >>> permissions of the corresponding kernel mappings.
> > >>>
> > >>> We also have to
> > >>> - put the region in an isolated mapping, and
> > >>> - move copying kexec's control_code_page to machine_kexec_prepare()
> > >>> so that the region will be completely read-only after loading.
> > >>
> > >>
> > >>> Note that the region must reside in linear mapping and have corresponding
> > >>> page structures in order to be potentially freed by shrinking it through
> > >>> /sys/kernel/kexec_crash_size.

Ah; I did not realise that this was a possibility.

> Now I understand why we should stick with page_mapping_only option.

Likewise, I now agree.

Apologies for guiding you down the wrong path here.

Thanks,
Mark.
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