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

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 22/08/2019 11:20, Wieczorkiewicz, Pawel wrote:
> > On 22. Aug 2019, at 12:07, Julien Grall <julien.grall@xxxxxxx 
> > <mailto:julien.grall@xxxxxxx>> wrote:
> > On 22/08/2019 08:44, Wieczorkiewicz, Pawel wrote:
> > > > > 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.
> > > What would be you suggestion then?
> > Cross-compiler are nowadays widely available. So build testing your changes in 
> > common code would be the minimum.
> I wish it was that simple. Nevertheless, I will try to prepare an environment to 
> perform such builds.
Cross-compiling the hypervisor is really easy ;).

1) Download the cross-compiler tarball (here one [1]) and uncompress it. You can 
also install the one provided by your distro.
2) Build Xen hypervisor. Here an example for arm64:

42sh> cd xen.git/xen
42sh> make XEN_TARGET_ARCH=arm64 CROSS_COMPILER=<triplet>-

In my case, I am using the Arm toolchain AArch64 GNU/Linux target 
(aarch64-linux-gnu). So the <triplet> would be aarch64-linux-gnu.
This is assuming you have the compilers binary in your PATH. If not, you can use 
give the full path:
CROSS_COMPILER=/opt/gcc-arm-8.3-2019.03-x86_64-aarch64-linux-gnu/bin/aarch64-linux-gnu-

> > In this case, as you dropped the const from the prototype, you will need to do 
> > the same in the declaration.
> Yes, but I see 2 options here:
> - Enable the feature also for Arm (I prefer that, but will not be able to test 
> that in nearest future)
I think some of the code can be made common. So we could possibly rely on x86 
for that. Additionally, IIRC, Konrad has a setup on the cubietruck for testing 
livepatch.
> - Keep Arm excluded and sprinkle code with #ifdef CONFIG_X86
Please no #ifdef CONFIG_X86 in the common code. If you don't plan to support 
Arm, then we should introduce a new Kconfig that will gate all those changes.
Cheers,

[1] 
https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-a/downloads
--
Julien Grall

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