On Sat, Sep 19, 2020 at 4:24 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> 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?
In effect, it would work like this:
/* Arch-specific, but there's a generic case for sane architectures. */
enum syscall_arch {
SYSCALL_NATIVE,
SYSCALL_COMPAT,
SYSCALL_X32,
};
DEFINE_MULTIARCH_SYSCALLn(args, arch)
{
args are the args here, and arch is the arch.
}
> 2) have you counted the syscalls that do and do not need that?
No.
> 3) how many of those realistically *can* be unified with their
> compat counterparts? [hint: ioctl(2) cannot]
There would be no requirement to unify anything. The idea is that
we'd get rid of all the global state flags.
For ioctl, we'd have a new file_operation:
long ioctl(struct file *, unsigned int, unsigned long, enum syscall_arch);
I'm not saying this is easy, but I think it's possible and the result
would be more obviously correct than what we have now.
