Re: Any future plan supporting livepatching in kernel for AArch64?

[Andrew Pinski <pinskia@gmail.com>]

On Wed, Sep 18, 2019 at 9:24 PM Bin.Cheng <amker.cheng@gmail.com> wrote:
>
> Hi,
> I read through previous messages which tried to support livepatching
> in kernel for AArch64.
> Following is the patch supporting mfentry:
> https://gcc.gnu.org/ml/gcc-patches/2016-03/msg00756.html
> And this is the last message about above thread:
> https://gcc.gnu.org/ml/gcc-patches/2016-04/msg01093.html
>
> Here is another patch trying to support a general option, however. it
> was not merged either.
> https://gcc.gnu.org/ml/gcc-patches/2016-12/msg01791.html
>
> If I read messages correctly, kernel part is not merged (partly)
> because of waiting for GCC.  As a result, we have to apply local
> patches, I am wondering if there is any future plan to support it on
> AArch64, or no one really uses it?

A GCC patch was merged for this already and is included in GCC 9.1.0 and above.
See https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Common-Function-Attributes.html#index-patchable_005ffunction_005fentry-function-attribute
And
https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/Instrumentation-Options.html#index-fpatchable-function-entry

Someone did not add it to the GCC 9 release notes though to highlight it.

Thanks,
Andrew Pinski

>
> I CCed patch authors as well as who joined previous discussions,
> please let me know if you don't want to be cced in this thread.
>
> Thanks,
> bin