ARM64: Domain Equivalent support in ARMv8

ARM64: Domain Equivalent support in ARMv8

[Ganapat Rao P Kulkarni]

Hi,

I want to make kernel code ( all sections/blocks mapped to kernel
code) as RO and change to R/W,  when ever hot-patch of kernel code is
required.
Also, R/W access changes should be available/visible to the core which
sets R/W and all other cores continue to have RO access.

This was easily done using Domain feature(by making Kernel Domain as
Manager, using DACR) on ARMv7.
However, on ARMv8, i see there is no domain support(in AARCH64) and
not able to find the alternative optimal way.

please suggest/share, if you have any ideas to do so.

regards,
Ganapat

ARM64: Domain Equivalent support in ARMv8

[Ganapat Rao P Kulkarni]

Hi Will/Catalin,

The requirement what i posted is doable on ARMv8?
If yes, can you please suggest the way to do it!

regards
Ganapat

On Tue, Dec 10, 2013 at 1:17 PM, Ganapat Rao P Kulkarni
<gpkulkarni@gmail.com> wrote:
> Hi,
>
> I want to make kernel code ( all sections/blocks mapped to kernel
> code) as RO and change to R/W,  when ever hot-patch of kernel code is
> required.
> Also, R/W access changes should be available/visible to the core which
> sets R/W and all other cores continue to have RO access.
>
> This was easily done using Domain feature(by making Kernel Domain as
> Manager, using DACR) on ARMv7.
> However, on ARMv8, i see there is no domain support(in AARCH64) and
> not able to find the alternative optimal way.
>
> please suggest/share, if you have any ideas to do so.
>
> regards,
> Ganapat



-- 
regards,
Ganapat

ARM64: Domain Equivalent support in ARMv8

[Catalin Marinas]

On Thu, Dec 12, 2013 at 07:48:19AM +0000, Ganapat Rao P Kulkarni wrote:
> On Tue, Dec 10, 2013 at 1:17 PM, Ganapat Rao P Kulkarni
> <gpkulkarni@gmail.com> wrote:
> > I want to make kernel code ( all sections/blocks mapped to kernel
> > code) as RO and change to R/W,  when ever hot-patch of kernel code is
> > required.
> > Also, R/W access changes should be available/visible to the core which
> > sets R/W and all other cores continue to have RO access.
> >
> > This was easily done using Domain feature(by making Kernel Domain as
> > Manager, using DACR) on ARMv7.
> > However, on ARMv8, i see there is no domain support(in AARCH64) and
> > not able to find the alternative optimal way.

Note that even on ARMv7, if you use LPAE domains are no longer
available.

So I'm not aware of any way other than creating a temporary mapping in a
per-CPU pgd. You could use a low address and TTBR0 so that it doesn't
interfere with the real kernel mapping.

-- 
Catalin

ARM64: Domain Equivalent support in ARMv8

[Ganapat Rao P Kulkarni]

Thanks.

On Thu, Dec 12, 2013 at 5:25 PM, Catalin Marinas
<catalin.marinas@arm.com> wrote:
> On Thu, Dec 12, 2013 at 07:48:19AM +0000, Ganapat Rao P Kulkarni wrote:
>> On Tue, Dec 10, 2013 at 1:17 PM, Ganapat Rao P Kulkarni
>> <gpkulkarni@gmail.com> wrote:
>> > I want to make kernel code ( all sections/blocks mapped to kernel
>> > code) as RO and change to R/W,  when ever hot-patch of kernel code is
>> > required.
>> > Also, R/W access changes should be available/visible to the core which
>> > sets R/W and all other cores continue to have RO access.
>> >
>> > This was easily done using Domain feature(by making Kernel Domain as
>> > Manager, using DACR) on ARMv7.
>> > However, on ARMv8, i see there is no domain support(in AARCH64) and
>> > not able to find the alternative optimal way.
>
> Note that even on ARMv7, if you use LPAE domains are no longer
> available.
>
> So I'm not aware of any way other than creating a temporary mapping in a
> per-CPU pgd. You could use a low address and TTBR0 so that it doesn't
> interfere with the real kernel mapping.
>
> --
> Catalin



-- 
regards,
Ganapat