Steven Rostedt píše v Pá 08. 11. 2013 v 07:43 -0500:
> On Fri, 08 Nov 2013 21:04:26 +0900
> Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote:
>
> > (2013/11/08 18:12), Petr Mladek wrote:
> > > This change is inspired by the int3-based patching code used in
> > > ftrace. See the commit fd4363fff3d9 (x86: Introduce int3
> > > (breakpoint)-based instruction patching).
> > >
> > > When trying to use text_poke_bp in ftrace, the result was slower than
> > > the original implementation.
> > >
> > > It turned out that one difference was in text_poke vs. ftrace_write.
> > > text_poke did many extra operations to make sure that the change
> > > was atomic.
> >
> > AFAIK, the main reason why text_poke is used is avoiding
> > RODATA protection (by alias mapping).
>
> That is correct, and the reason ftrace didn't do that is because it
> would be quite expensive to map 22,000 addresses for each change.
I see. I am going to prepare v3 with the following changes:
+ use text_poke in text_poke_bp back again because it is not
effective to make the pages rw only for a single address;
the alias mapping is faster here
+ use the faster text_poke_part only in text_poke_bp_iter;
the caller of this function will be responsible for
making the code rw
+ I will rework the error handling as suggested in the other
mails; I will try to add some also for text_poke.
Thanks a lot for hints.
Best Regards,
Petr
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