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

[Christoph Hellwig]

On Fri, Sep 18, 2020 at 02:40:12PM +0100, Al Viro wrote:
> >  	/* Vector 0x110 is LINUX_32BIT_SYSCALL_TRAP */
> > -	return pt_regs_trap_type(current_pt_regs()) == 0x110;
> > +	return pt_regs_trap_type(current_pt_regs()) == 0x110 ||
> > +		(current->flags & PF_FORCE_COMPAT);
> 
> Can't say I like that approach ;-/  Reasoning about the behaviour is much
> harder when it's controlled like that - witness set_fs() shite...

I don't particularly like it either.  But do you have a better idea
how to deal with io_uring vs compat tasks?