Re: [PATCH 1/9] kernel: add a PF_FORCE_COMPAT flag

Arnd Bergmann
2020-09-20T20:49:29Z

On Sun, Sep 20, 2020 at 9:28 PM Andy Lutomirski <luto@kernel.org> wrote:
> On Sun, Sep 20, 2020 at 12:23 PM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > On Sun, Sep 20, 2020 at 08:10:31PM +0100, Al Viro wrote:
> > > IMO it's much saner to mark those and refuse to touch them from io_uring...
> >
> > Simpler solution is to remove io_uring from the 32-bit syscall list.
> > If you're a 32-bit process, you don't get to use io_uring. Would
> > any real users actually care about that?
>
> We could go one step farther and declare that we're done adding *any*
> new compat syscalls :)

Would you also stop adding system calls to native 32-bit systems then?

On memory constrained systems (less than 2GB a.t.m.), there is still a
strong demand for running 32-bit user space, but all of the recent Arm
cores (after Cortex-A55) dropped the ability to run 32-bit kernels, so
that compat mode may eventually become the primary way to run
Linux on cheap embedded systems.

I don't think there is any chance we can realistically take away io_uring
from the 32-bit ABI any more now.

Arnd