Re: [PATCH] Add a text_poke syscall v2

Jiri Kosina
2013-11-29T23:25:06Z

On Fri, 29 Nov 2013, Oleg Nesterov wrote:

> > > Andi, et al. I am going to discuss the things I do not really
> > > understand, probably this can't make any sense, but...
> >
> > I think it's enough to set the dirty bit in the underlying
> > struct page, no need to play games with the PTE.
>
> Ah, sorry for confusion, I guess you misunderstood.
>
> I meant, perhaps sys_text_poke() doesn't the in-kernel text_poke
> machinery altogether?
>
> Can't we invalidate pte (so that any user will stuck in page fault),
> update the page(s), restore the pte and drop the locks?

Do you think this'd be faster than the int3-based aproach?

We have moved from using stop_machine() to int3-based patching exactly
because it's much more lightweight.

> This way sys_text_poke() won't be x86-specific, and it will be per-mm.

Good point, it'd be really nice to have this as an alternative on archs
where breakpoint-based patching wouldn't be possible for some reason.

--
Jiri Kosina
SUSE Labs