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SubjectRe: [PATCH 1/2] vmalloc: New flag for flush before releasing pages
On Thu, 6 Dec 2018 at 20:21, Andy Lutomirski <luto@kernel.org> wrote:
>
> On Thu, Dec 6, 2018 at 11:04 AM Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
> >
> > On Thu, 6 Dec 2018 at 19:54, Andy Lutomirski <luto@kernel.org> wrote:
> > >
>
> > > That’s not totally nuts. Do we ever have code that expects __va() to
> > > work on module data? Perhaps crypto code trying to encrypt static
> > > data because our APIs don’t understand virtual addresses. I guess if
> > > highmem is ever used for modules, then we should be fine.
> > >
> >
> > The crypto code shouldn't care, but I think it will probably break hibernate :-(
>
> How so? Hibernate works (or at least should work) on x86 PAE, where
> __va doesn't work on module data, and, on x86, the direct map has some
> RO parts with where the module is, so hibernate can't be writing to
> the memory through the direct map with its final permissions.

On arm64 at least, hibernate reads the contents of memory via the
linear mapping. Not sure about other arches.

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