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

[Al Viro]

On Sat, Sep 19, 2020 at 03:53:40PM -0700, Andy Lutomirski wrote:

> > It would not be a win - most of the syscalls don't give a damn
> > about 32bit vs. 64bit...
> 
> Any reasonable implementation would optimize it out for syscalls that don’t care.  Or it could be explicit:
> 
> DEFINE_MULTIARCH_SYSCALL(...)

1) what would that look like?
2) have you counted the syscalls that do and do not need that?
3) how many of those realistically *can* be unified with their
compat counterparts?  [hint: ioctl(2) cannot]