Re: change "microcode: Use fallthrough attribute on clang 10 and 11 too." broke the build for me

[Chris Hanson]

Where did you find out about W^X ?

I have an x86-64 machine running macos 11.2 and scheme works fine there, 
mostly. Specifically, if I build the normal binaries, they seem to run 
just fine. However, if I build a macos app, it fails to run at all. 
Perhaps the W^X restriction applies only to apps?

On 2/15/21 9:11 AM, Taylor R Campbell wrote:

> > Date: Mon, 15 Feb 2021 00:17:45 -0800
> > From: Chris Hanson <cph@chris-hanson.org>
> >
> > > > I'll make the change and cherry-pick to release-11, unless you want to
> > > > do it.
> > > Go for it!
> > Done.
> Thanks!
>
> > I notice that there are several other microcode changes that seem
> > related to the new macs. Should those be cherry-picked too? If you agree
> > could you please select the relevant ones?
> >
> > I'd like to release 11.2 with working support for the new macs.
> Feel free to cherry-pick them, but unfortunately it's not that easy --
> after making enough changes to get the microcode built, I learned that
> W^X is now mandatory on macOS/aarch64.
>
> So we need to teach the ucode (declare-compiled-code-block and gc) to
> store compiled blocks in a separate PROT_READ|PROT_EXEC heap written
> with the MAP_JIT API, and keep the main heap PROT_READ|PROT_WRITE.