Re: [PATCH v2 02/13] uprobes: allow ignoring of probe hits

[David Long]

Sorry for the delay, all this week it's me that's traveling.


On 10/28/13 14:54, Oleg Nesterov wrote:
> David, sorry for delay.
>
> On 10/19, Oleg Nesterov wrote:
> > On 10/15, David Long wrote:
> > > @@ -1732,9 +1732,6 @@ static void handle_swbp(struct pt_regs *regs)
> > >   		return;
> > >   	}
> > >
> > > -	/* change it in advance for ->handler() and restart */
> > > -	instruction_pointer_set(regs, bp_vaddr);
> > > -
> >
> > Well, this looks obviously wrong. This SET_IP() has the comment ;)
> >
> > Note also that with this breaks __skip_sstep() on x86.
>
> Hmm. Thinking more, it seems that this patch has another problem.
>
> IIUC, the whole point of arch_uprobe_ignore() is to avoid
> handler_chain() if the condition was not satisfied, so you need
> to call it before handler_chain() ?

Yes, you're right.  I can see now that is a bad merge of an earlier 
version of the patch.  I have just tested the fix.  Thanks for finding this.

> Otherwise this logic should go into can_skip_sstep() and we simply
> do not need the new hook, just we need to tweak the (ugly)
> UPROBE_SKIP_SSTEP logic.
>
> Oleg.


-dl

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