Re: [Xen-devel] [PATCH 09/14] livepatch: Add per-function applied/reverted state tracking marker

[Julien Grall <julien.grall@xxxxxxx>]

Hi Pawel,

On 8/21/19 9:19 AM, Pawel Wieczorkiewicz wrote:
> Livepatch only tracks an entire payload applied/reverted state. But,
> with an option to supply the apply_payload() and/or revert_payload()
> functions as optional hooks, it becomes possible to intermix the
> execution of the original apply_payload()/revert_payload() functions
> with their dynamically supplied counterparts.
> It is important then to track the current state of every function
> being patched and prevent situations of unintentional double-apply
> or unapplied revert.
>
> To support that, it is necessary to extend public interface of the
> livepatch. The struct livepatch_func gets additional field holding
> the applied/reverted state marker.
>
> To reflect the livepatch payload ABI change, bump the version flag
> LIVEPATCH_PAYLOAD_VERSION up to 2.
>
> The above solution only applies to x86 architecture for now.
Is this going to break livepatch on Arm? If so, do you have any plan to 
fix it?
[...]

> diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h
> index 2aec532ee2..a93126f631 100644
> --- a/xen/include/xen/livepatch.h
> +++ b/xen/include/xen/livepatch.h
> @@ -117,7 +117,7 @@ int arch_livepatch_quiesce(void);
>   void arch_livepatch_revive(void);
>   
>   void arch_livepatch_apply(struct livepatch_func *func);
> -void arch_livepatch_revert(const struct livepatch_func *func);
> +void arch_livepatch_revert(struct livepatch_func *func);
I doubt livepatch on Arm will compile after this change.

>   void arch_livepatch_post_action(void);
>   
>   void arch_livepatch_mask(void);
Cheers,

--
Julien Grall

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