Please Please put back Sys/io.h emulation for armhf and possibly aarch64

[Phil Blundell]

On Wed, Jun 16, 2021 at 12:14:29PM +0100, Luís Palma Nunes Mendes via Libc-alpha wrote:
> The commit that removed the support, according to Carlos O'Donell was
> this one:
> The rationale is given in the commit:
> 
> commit 6b33f373c7b9199e00ba5fbafd94ac9bfb4337b1
> Author: Florian Weimer
> Date:   Wed May 29 16:53:09 2019 +0200
> 
>     arm: Remove ioperm/iopl/inb/inw/inl/outb/outw/outl support
> 
>     Linux only supports the required ISA sysctls on StrongARM devices,
>     which are armv4 and no longer tested during glibc development
>     and probably bit-rotted by this point.  (No reported test results,
>     and the last discussion of armv4 support was in the glibc 2.19
>     release notes.)

I must admit I hadn't noticed this commit at the time.  I believe Florian is
correct that only StrongARM devices actually exposed any ISA ports as part
of the default kernel configuration, though you're also correct that it's
still possible even today to patch your kernel to do that.

I don't know offhand (and I haven't checked the archives to find out)
whether this code was causing any particular problem or whether Florian
just removed it for reasons of general hygiene because it seemed to be
unused.

Equally, there's no reason that the code that was removed by this commit
needs to live in glibc.  You could just as easily build it into a separate
library, "libioperm" or something, and link your application against that.
So on balance, I'm not sure there's a compelling reason to put this code
back into glibc.

p.